Ep 15: Rebuilding a Nitro Engine

[00:00:10] RC Plane Lab, a podcast for anyone interested in rc airplane. We’ll share tips and tricks on how to build models and talk about successful flights, epic crashes and everything in between. Visit us at rcplane labcom to sign up for our email list and to ask us questions. You can also text us or leave us a voicemail at 818-351-9846. Please help us out by rating and reviewing us in your favorite podcast app. Thanks for spending time with us today. Now here are your hosts: Ron and Tom hello.

[00:00:38] Everyone and welcome to the RC Plane Lab podcast. This is Ron and I’m Tom. On today’s episode, we’re going to be kind of continuing from last week’s with our nitro episode theme and we’re going to be talking about rebuilding nitro engines. These, these engines last a long time as long as you take care of them, and one of the steps to taking care of them is keeping them running right by rebuilding them from time to time when they need it. So I actually have never rebuilt.

[00:01:09] An airplane engine. I have done them for nitro cars before, but never for a nitro airplane engines. You’ve been flying for a long time, so how many engines have you rebuilt, conservatively speaking?

[00:01:23] 15. Oh, let’s say yeah, so quite a few. Then, yeah, yeah, I’m, I’m not an expert, I’m not clarence lee, who is a legend in the airplane engine market, if you will, or realm or arena, but yeah, I’ve done my fair share and they, they all have run after I’ve rebuilt them, so I consider that a.

[00:01:46] Success yeah so you brought him up in the last episode we talked about too I’m not familiar with him.

[00:01:53] Who is that? So, clarence, lee is like I said, he’s, if you’ve been flying for a long time, you the name at least, and he’s. He’s been affiliated with a lot of different model engine companies, I think, but primarily kmb, which is a manufacturer. That long story short, they’re. They’re not operating as they used to, they’re operating under a, a big umbrella.

[00:02:25] Company now called the model engine corporation or model engine company of america, mcoa for short. But anyway, clarence lee was involved with kmb and he was a tuner. He produced custom engines. So you would order an engine from clarence lee and it would usually be a kmb and depending on what you wanted, it was a 61 or maybe it was a 40 or whatever. But he would do things, he would. He would modify them for max performance, he would. He would fiddle with the porting by grinding on the

[00:02:57] On the sleeve or he’d he’d fill in ports in the crankcase and re. I don’t want to say recast them, but just basically tweaking these two-stroke model engines for maximum performance, mostly for racing guys. But his engines were very. They ran very, very well and he also for a long time. He contributed to a lot of the paper magazines that you don’t see around.

[00:03:29] Around much anymore thanks to the internet and google and forums and things like that. But he used to write a column in rcm and I mean you could write into rcm with a with an engine question and he would write an answer and then the following issue in the next month’s issue and he always had the answer. I mean the guy- and he’s still alive. Actually he’s still producing high-end knb engines that you can order and he does it. He does things the old way you can.

[00:04:02] You can call him to order and you can. You can mail him a check and order. That way he doesn’t do anything online. But yeah, just yeah. I have a tremendous amount of respect for the guy just because of his knowledge and skill with these two-stroke nitro motors. So when are you talking like the? The heyday for all that would have been? Oh, certainly, certainly the 80s and early 90s, for sure, and I imagine with his, with the, the level of skill and knowledge that he had, I imagine.

[00:04:37] He probably started with engines in the 50s and 60s I bet as a kid that’s probably why I haven’t.

[00:04:43] Heard of him then because that’s way before my time in the hobby yeah just do a just do a quick.

[00:04:48] Like google search clarence lee model engine and there’ll be a lot of stuff out there.

[00:04:53] On him okay I should remember to do that after this so that’s cool yeah one of these days.

[00:04:59] I’m going to get my hands on one of his engines and it’ll be a it’ll be a cherished possession.

[00:05:05] For sure. So if he still does it, though, you can just order him like: I mean, what do you do? Tell him? Tell him, like the size you need, what you’re putting it on, and he goes from there, or? Or? How does that all?

[00:05:14] Yeah, that’s basically exactly. You call him up and either his wife, I think, answers or he answers the phone. You call him up and you say: hey, I want to order an engine. And then he’ll probably ask you a few questions like: okay, well, what size? What are you using it for? Is it, is it a pylon racing engine? Is it a pattern plane engine? What are you? What are you going to do with this thing? And then he will tune it and tweak it accordingly and then in about a month or so he’ll send it to you when he’s done with it, like he makes them to order. Well, why haven’t you done it?

[00:05:48] Yet well, from like, I don’t know for sure, but I imagine they’re. They’re probably fairly pricey, fairly expensive, worth every penny, I’m sure. But so far I haven’t, I haven’t had a need for an engine that performs like that. I’m okay with my little sport airplanes that have just basic stock engines. But one of these days, one of these days- yeah, well, it almost sounds.

[00:06:14] Like time might be, might be running out, so maybe you ought to just get one, to have one on hand. Well, I mean, I don’t mean to sound bad about it, but no, no, if he was around the 50s and 60s- and this is something you’re you’re talking about- that you’d like to cherish.

[00:06:27] In a prized possession. Maybe it’s time just to order it, and- and you might be right, yeah, yeah, maybe with this big economic stimulus that the government’s going to give us, maybe I’ll spend a little bit of.

[00:06:37] That on one of these things, there you go, see plans already, there we go anyway, don’t even have it yet. That’s the easiest way to spend it, yeah, isn’t it all right? Well, let’s, let’s get back. I’m. I’m sorry, I didn’t mean to get us off topic on that. So yeah, rebuilding nitro engines: how do?

[00:06:58] When it’s time to rebuild. Yeah, there’s. There’s a couple different ways to know. For me, one of the one of the biggest telltale signs is a difficulty starting an engine. That hasn’t been difficult to start before and that’s usually related to compression and you can feel that you can over time. It’s hard to tell when an engine is losing compressing, because you’re flying it and if you hand start it, like I do, you have a hands-on feel when the compression what, what it should feel like. But basically I mean you should not be able.

[00:07:33] To turn an engine over with a prop on it with one finger. If you can take one finger and pull the propeller through the compression stroke and, and passed, chances are it’s time for a rebuild. But difficulty starting and then loss of performance are the two factors that

[00:07:52] I that I sort of look for, and so that’s something that obviously depends on the engine how long they last. But, like usually, and so that’s a it’s probably an unfair question, but how long, like how long should you expect to get out of an engine between the time you buy it, if you break it in properly, if you treat it well, how long should you get, like, gallons of fuel wise before you?

[00:08:17] Normally have to rebuild them. Yeah, that’s, that’s a good question. Actually, it is hard to tell because so many variables play into how long one of these little engines will last. But I mean, if it’s, if you run them on the conservative side, which is what I do, you run them on the kind of the rich side and you don’t get them hot, and the heat is, is really the biggest enemy, because these things are air cooled, they’re not liquid cooled, so they’re they’re.

[00:08:47] Highly dependent on airflow over the fins to cool them. So the installation plays a plays a big role, like even if even a properly tuned engine can still run hot if there’s not enough air.

[00:09:00] Flowing over it to cool it so like if it’s inside of a cowl that doesn’t get the airflow that’s.

[00:09:05] Gonna exactly hurt. It’s okay. So that’ll hurt his life exactly okay. So and- and that was something I’d like to try to circle back to later about, about cooling and cowling and things like that, but anyway it an engine that’s, that’s installed such that it gets plenty of airflow and you run it conservatively. I mean five gallons of fuel. I mean I’ve got, I’ve got an engine on this old contender over here. It’s an old SuperTigre, so it’s exposed, it’s not a fully cowled in engine.

[00:09:37] And I run it conservatively, I don’t tune it for max performance. This engine is jeez. It’s 15, 16 years old and I’ve never rebuilt it. It runs like it, like it did the day it was new, and I probably have two and a half to- I’m estimating here- but two and a half to four gallons of fuel through it and it’s showing no signs of needing a rebuild. So if you take care of them, they really will last a good long time. Well, that’s the thing too about them really is.

[00:10:07] You’re not using them every day exactly, so it’s it’s not something to where, it’s like a car where you drive it every day and you’re worried about going through it. So really, to me five gallons doesn’t sound like a lot. But in the grand scheme of things, when you go out to a field and fly it three or four times in a day, you’re running what? Eight ounce tank 16, 32 ounces through it maybe, yeah, so you’re not running much through it at all in that amount of time. So right, and I you don’t get out there every weekend most of the time either, especially for us.

[00:10:37] Where we have the, the cold weather that hits in and we can’t always get out windy days and such. So yeah, I mean I guess- and most people don’t just have one plane they fly either- so going through them- that I guess those, those five gallons get spread out over many years and you

[00:10:52] Don’t really even think about it. Yeah, yeah, that’s exactly right and I would say that’s probably on one end of the spectrum. On the other end of the spectrum is somebody who constantly flies for max performance. They fly at wide, open throttle the whole time and maybe their engine is cowled in and not getting the cooling it needs. That engine may not last a gallon of fuel, it may not last a flying season. So it’s it’s highly dependent on a lot of variables. But, like, like I said just a little bit ago, the, the

[00:11:26] Biggest factors to look for when it’s time is difficulty. Starting that’s for me is like the first, the first kind of aha and then loss of performance is usually a good indicator.

[00:11:40] Too like difficulty starting the first thing you should always do though am I correct is check.

[00:11:44] Your glow plug, absolutely. Yep. Yeah, if you, if you’ve eliminated most of the stuff that we covered in the last episodes about starting, you’ve got good glow heat and you’ve got a good prime and the engine still kind of refuses to fire off and it and it just kind of feels weak or lazy on the compression, then it’s time to start looking at, looking at- pull the head off, look at the cylinder, look at the piston, and you can usually tell by looking.

[00:12:15] At them. So when it’s okay, when you’ve gone through all that and it’s time to do it like roughly, how long does it take to rebuild an engine? Not long if you have all the parts.

[00:12:27] And- and you have a good technique- it you can rebuild one of these little suckers in an hour. I mean, no, okay, yeah, that’s less than I was thinking, yep, doesn’t take long at all. And then, like when you

[00:12:41] Go to order the kit then what’s what’s included in the rebuild kit for airplane engines they’re not.

[00:12:47] They’re not really sold as a rebuild kit per se. Usually you can buy a sleeve and liner together, which is the- I’m sorry, the piston and liner together as a match set especially for abc engines. But on the airplane engine side that they’re usually sold just in the pieces. So you order the parts you need for your rebuild and that is your kit. I know on, I think, on some of the car engines- yeah, the nitro engines for cars- I think they may be sold like what you’re.

[00:13:23] Talking about. Yeah, so the only experience I have rebuilding a nitro engine was a traxis 3.3 And that was gosh, probably 10, 12 years ago, so I don’t remember exactly how I did it, but it was. It was a kit. It came with everything you needed and you didn’t have to go and get separate parts, so I didn’t realize the.

[00:13:40] Airplanes were a little bit different, right, yeah, and for me a rebuild is basically, I guess there’s different levels. If you want to, if you want to get into that, you can for what the parts cost. These days to completely rebuild an engine like all new parts, it’s almost just cheaper to buy a new engine, but it but you can actually get away. And the parts that wear are really the piston and the sleeve, usually the connecting rods are, are usually pretty.

[00:14:14] Durable. They get a lot of lubrication from our, from our fuel, even when they run a little bit on the lean side. The wear really shows up on the piston more than anything. So usually what? What I do when it’s time for a rebuild is I’ll order the piston and sleeve and then any necessary gaskets. Usually there’s a head gasket maybe, or a shim if you will, and there’s usually a back plate gasket. On some of the older engines- like I’m looking at my old irvine 40 here that I’m planning-

[00:14:47] On putting on the dualist project. It’s, it has a what I call a two-piece crankcase, so the snout of the crankcase is actually a bolt-on affair and it also requires a gasket. So that’s what I do: I order a piston and sleeve or a ring for the piston if. If it’s a ringed engine, which that’s semi-uncommon, right it’s. It’s not as common as it used to be, but you can still actually buy ringed engines out there. I think the, I think the os 55ax I might be mistaken, but there are still. There are still ringed.

[00:15:22] Engines out there and actually a ringed engine makes the rebuild a lot cheaper if you just stick to replacing the ring for the piston and the liner if the liner is showing, where usually on a ringed engine a fresh ring will restore the compression usually- not always- but so that’s what I do. I start with a piston and a sleeve or a ring if it’s a ringed engine, and then a set of bearings and that’s usually, and any gaskets and that’s usually all I usually replace. Because if you

[00:15:54] Start buying connecting rods or crankshafts usually you don’t need to replace those because they’re.

[00:15:59] Usually in pretty good shape after you rebuild it is. Is that pretty much like a new engine? Then can you expect the same duration out of that rebuild that you can from a new engine, or do you get less?

[00:16:09] Life out of it. Nope, you can. You can absolutely get the. You can expect to get the same amount of life, because they’re factory original parts and in the case of abc engines you really have to buy the piston and sleeve as a match set because that’s how they’re manufactured and, yeah, I mean, when you put those in there, it’s, it’s, it’s a new engine, I mean you’re. You have to go through the break-in process just like it was a new engine. They’re factory parts so they’re made to the same specs as the engines that roll out of the factory. So, yeah, for you can, you could reasonably expect.

[00:16:40] To get the same amount of life after a rebuild yep walk us through the process then.

[00:16:46] What are the steps to doing it well you disassemble it and put it back together.

[00:16:52] Well, that’s easy then. So, right, right. So, yeah, there’s, there’s a technique that I’ve used, that I learned a long time ago from reading, or what have you. But yeah, basically you, I mean you, you do, you take, take the engine apart and you clean it as best you can. There’s lots of, there’s lots of ways to do that. I’m not going to get into cleaning an engine, because we could talk hours about different methods of getting them clean, but whatever method you choose, try to get all the gunk and stuff, especially off of the fins on the outside of the engine, because we’ve

[00:17:25] Talked about that. Right, the fins are what cools the engine. If they can’t do their job, then you got a hot running engine and it requires a rebuild more often, and then we’re talking about this again. So, disassemble the engine, clean it, and then there’s some little tricks that you, when disassemble engine, that you’ll need to know to completely disassemble engine and specifically to get the piston and the sleeve out. Usually there’s some little process that you have to follow in order to get those pieces out of there, and usually what that consists of is you have to, obviously pull.

[00:18:00] The head off, pull the back plate off and then somehow you have to get the sleeve out of the cylinder with the piston still in the cylinder, because you can’t slide the piston off of the crank pin- yeah, because it’s connected to the connecting rod right. With the sleeve still in there’s not enough play. So that’s the real trick is getting that sleeve out of the engine with the piston in there. And a little trick I learned a long, long time ago is in our flight boxes we keep usually old glow plug.

[00:18:34] Washers, those little copper washers that crush when you put the blow plug on. I usually, I usually hang on to the old ones. I don’t know why. It’s just a bad habit, but it’s a good thing I do because what I do is I’ll, once you have the head off the engine, in the back plate I move the piston to bottom, dead center, and I take a couple of those copper washers and I’ll throw them down there on top of the piston. And if you look down into the top of the engine, down at the piston, you’ll see the exhaust port and

[00:19:04] The intake ports and all these little ports that are cut into the sleeve so what I’ll do is I’ll take.

[00:19:10] That copper washer. So hold on. Sorry, I don’t. I don’t mean to interrupt you, but well, okay, so when you pull the head off the, the head is separate from where the sleeve and piston is, so the sleeve and piston.

[00:19:21] Stay on the engine and the head comes off right. Yeah, I’m sorry. Yeah, it’s not a. It’s not a jug like an old volkswagen engine- if you’re familiar- or are real airplane engines. On the four strokes, they’re that way, but we’re not. I’m not talking about four strokes. Okay, on these two strokes. Yeah, the head is just what it says. It’s just the cap, basically to the cylinder of the of the engine, so the jug itself doesn’t come off. So, yeah, we’re looking down at the top, down through the through, where the head would be down at the top of the piston, and I’ve got my couple of brass washers.

[00:19:54] In there. What I’ll do is I’ll move that piston up just a little bit and I’ll move those brass washers such that they’re partially in either the exhaust port or one of those intake ports or whatever, and then I can use that piston kind of as leverage against that washer to put pressure on the sleeve to push it out of the crank case, because it doesn’t matter because the ports you’re

[00:20:18] You’re talking about that you can mess up are going to be replaced with a new sleeve right that’s all.

[00:20:23] Built in, right, right, okay, and even if you were, even if you were rebuilding a ringed engine, you could use the same process, because that copper washer will crush and not deform any steel or aluminum parts, because it’s softer than those. Okay, yeah, so, and then I, I also use a little heat, so I’ll, I’ll grab my, excuse me, I’ll grab my, my covering, not my iron, but my heat gun that I use for covering, and I’ll, I’ll heat that, that cylinder up, and you want to wear.

[00:20:59] Gloves, but usually a little bit of heat and those copper washers to apply the pressure will usually allow you to kind of push that sleeve out to the point where you can grab it with your glove and then pull it the rest of the way out. That’s. That’s a little trick I learned a long time ago. Yeah, I.

[00:21:14] Kind of seem to remember there was a an oven involved when I did the, the rc car engine a long time ago, but I didn’t know if that was right or not, so I didn’t want to say anything until you said:

[00:21:23] Something about heat, because I didn’t want to sound weird. The oven, the oven, the oven method is what I use, and I’ll talk about this in a little bit to get the bearings out of the crank case.

[00:21:33] Okay another little trick and maybe that’s what I used it for I don’t I don’t remember it’s been a long.

[00:21:37] Time, yep, yep. So once you’ve got the sleeve out, then you can. You can reach in there and pull the connecting rod off, the crank pin, which will usually have the piston attached to it, and pop that out of the engine, and if that’s all you’re replacing, you don’t have to take it apart any further. Myself, I usually do bearings as well, and the reason I do that is because I do have a bad habit occasionally of forgetting to put after run oil and over years after.

[00:22:10] I’m done running and over years bearings do get gritty and usually by the time one of my engines needs a rebuild, the bearings are due for replacement as well. So to get those out, that’s where the oven trick comes in. Obviously you’re going to pull the prop nut and the washer off and then you have to get that prop drive washer off too, and there’s lots of different ways that those are attached to the engine. Some of them use a what I call a woodruff key. So that’s like you.

[00:22:44] Know if you’ve ever taken apart like a briggs and stratton engine. There’s that kind of half moon shaped key that’s fits in a recess, and the crankshaft and then the flywheel fits over that same idea. Or there’s a tapered collet which, when you slide the drive washer on it, fits over that tapered collet and then first time you crank the prop down on it, it sets that drive washer in place- semi permanently, I’ll add, because they’re hard to get off, especially if it’s an engine that’s been

[00:23:16] Through a lot of heat cycles. So to get that drive- the prop, drive hub or drive washer or whatever you want to call it off- I use a cool little tool that I modified just slightly so I’m not. You could use a screwdriver, and I’ve seen people use screwdrivers and heat, but usually that ends up in leaving gouges on your crankcase. I like my stuff to look nice, so I don’t. I don’t want those gouges on my crankcase. So what I did is I went to autozone. It’s been a years ago, I’m sure they still.

[00:23:48] Sell them- and I bought a tool- it’s called a, a battery terminal puller, and it’s actually a little two. Yeah, it’s actually a little two jaw puller. That’s very small because it’s only designed for battery terminals. It’s not like a flywheel pull or anything like that. I did modify the jaws slightly. I ground them kind of to a point so that I could get behind that drive washer with those jaws and use that to pull the washer off. And it works great. I mean, I’ve used it for years and years. In fact, I don’t even try to pull them off by hand anymore, I just grab that tool.

[00:24:23] Put it on there and they pops them right off. So once you’ve got the drive washer off or the drive hub- it’s called a lot of different things, I call it a drive washer- then you basically either get the crankshaft out- and heat always helps here, because those crankshafts are usually- I don’t want to say they’re- press fit, because they’re not, but over time with the heat and cold and heat and cold and the and the oil that’s in our fuel getting baked on there, those crankshafts are usually stuck on the inner races of the bearings. So sometimes they need a little help.

[00:24:57] And heat is the is the help, and what I do is I just basically I take the engine, set it on its, on the back plate or where the back plate would be, and then I take a piece of wood on the on the end of the crankshaft and then give it a good smack with a, with a handle of a screwdriver or something. Usually that’s enough to pop them out of there if you can’t get them out any other way. And then at that point you’ve pretty much got a bare crankcase, you’ve got the sleeve and the piston, the connecting rod, those are all out. You’ve got the head obviously off, and

[00:25:32] The back plate off. Hopefully by now you’ve you’ve taken the carburetor off because you don’t want to break it in the in the course of manhandling this thing to try to get the pieces off, and now you have the crankshaft out. So now you’ve got this basically bare engine block with the bearings still in it, and the trick I use to get the bearings off is: I said don’t tell my wife this, but I set the oven to 250 degrees. I take a, an old pan, set the engine in this.

[00:26:03] Pan, put it in that oven for about 10 to 15 minutes, let it get good and warm, and then, with a pair of gloves- that’s very important, don’t grab it with your bare hands. Please grab that, take that engine out of there. And then this sounds really, really barbaric. But what I do is I’ve got this big wooden it’s. It’s like a two by four, two by six plank kind of a thing, but it’s not pine, it’s harder than that, it’s a maple. It doesn’t matter, as long as you got some wooden block, that’s.

[00:26:35] Softer than the engine. You basically, just now that the engine’s hot, you take it, you grab it and you basically smack it on this wooden thing as flat as you can, on the back plate, where the barrel, where the back plate mounts, and usually that is enough to knock the bearing out of the back.

[00:26:53] It may take a couple tries until you develop your technique or whatever, but I’ve gotten to where I can usually get them on the first try without having to reheat them. So that’ll get the rear bearing out. The front bearing is a little trickier and a little trick that I use is same thing: heat from the oven or a heat gun, if you want to use that, and what I do is I’ll take the crankshaft and instead of putting it in the engine from the back, I’ll turn around and put it.

[00:27:23] In from the front and usually the friction of that crankshaft, and I can usually wiggle it when it’s hot and pull that front bearing out, and then that’s it. The assembly is the exact opposite of that. You start with the bearings, put those in. A little trick that helps me is I’ll I’ll put the new bearings in the freezer like before I get started, so when I’m ready for them they’ll be nice and cold and just slightly smaller than the bores that they’re going into, and usually I can pull them out of the freezer and they’ll slide right in the crankshaft as they warm up. They get that nice tight.

[00:27:56] Fit and then yeah put it back together just exactly the way it came apart and then after it’s.

[00:28:03] Done make sure you break it in like it’s a new engine exactly yep yeah the bearings are fine you.

[00:28:08] Know everything, all the pieces are fine. The only thing we’re doing is we’re trying to wear in that new piston and sleeve fit so you get that good, nice seal and you get a good long life.

[00:28:17] Yeah break it in just like it was a new engine yep that way you’re not doing this again in a couple.

[00:28:22] Months exactly. Yeah, hope I didn’t confuse anybody. But once you get it down, you get a develop or a technique developed it goes pretty quick. Like I said, I can if I don’t run into any weird issues like a, a seized bearing that’s welded itself to the crankshaft, which I’ve had that before. As long as you don’t run into anything like that, an hour easy. So two stroke versus

[00:28:49] Four stroke on those, then okay, like, which one lasts longer, or is there a difference? Like, when I say last longer, I mean like if you’re taking care of it the same way and all things equal, do you get a longer, more fuel run through a two stroke or a four stroke? So I’ll have to be honest.

[00:29:07] Of all the four strokes I’ve ever owned, I have not had to rebuild any of them ever. I don’t know now. I mean I don’t know if that’s because they’re just that much more durable. It could also be that I just haven’t used them as much as I’ve used the two strokes over the years. I have rebuilt a few, not because they were worn out. Well, maybe not because they were worn out, but they were used engines that I purchased and they felt low on compression. So I would go ahead and do a rebuild just to.

[00:29:39] Just to know that I’m starting off with something good. Or you’ve never had one. You bought brand new that you had to rebuild, not once, yep, yeah. So, like I said, take that with a grain of salt. It could be because I don’t I don’t run as much fuel through them because they’re I don’t have as many of them. So, yeah, take that for what it’s worth, but I have not had to rebuild a four stroke because it was worn out, at least not one that I wore out the difference.

[00:30:09] Between rebuilding them. Then what’s is there any more? I mean, obviously there’s going to be more that goes into to doing a four stroke, because it’s it’s a little more involved engine. But

[00:30:21] Is it much more difficult to do? I wouldn’t really say the difficulty is any greater than a two stroke. It’s just that there’s more pieces and it’s it’s very important to put those pieces back where they go and to not have extra pieces when you’re done. But no, the process really isn’t any more difficult now. Having said that, I would say that if you’ve never rebuilt even just a two stroke before you tackle a four stroke, maybe go ahead and do it. But

[00:30:56] Maybe have some- I don’t want to say supervision, but maybe have somebody around who’s done it before- because it is very easy to lose parts that are under spring pressure, especially when we’re talking about the valve train and also there’s a. There’s a key element when, when you’re dealing with four stroke is that is that valve timing, so these four strokes use a camshaft to actuate the valves, which is driven off the crankshaft, and that the timing of those two, how they’re geared together, is extremely important. You get that wrong. I mean, obviously the engine is not going to run right, but

[00:31:32] Also, if you get it really wrong, you can. You can smack the piston with a valve and that’s not good, we don’t, we don’t want anybody doing that. So if you’re going to try to tackle one yourself, it’s fine, you can do it. But just be very, very careful with that, with that camshaft crankshaft interface, because take pictures with your phone as you’re taking it apart, or just or make a mental note. Some people, they, they- scratch little lines on. I don’t recommend doing.

[00:32:05] That I’m not a big fan of scratching on engine parts, but just do whatever you can to make sure you get that interface exactly right when you put them back together. Otherwise, I mean, it’s it’s just a mechanical little thing and if you take it apart and you put it back together the way it came,

[00:32:24] Apart, it should run just fine. So it doesn’t sound like there’s too much to them, like in general. Obviously the four strokes are a little bit more difficult, but it doesn’t sound like there’s too much to these engines and it’s it’s a good thing that if you need to just kind of try and tackle it yourself, if you’re comfortable, if you feel like you can do it, don’t be afraid of it. Just give it a shot and see what. What comes of it. Yeah, if you have even just average mechanical

[00:32:47] Ability. You can. You can definitely rebuild one of these, and we say rebuild because we’re just taking old parts out and putting new parts in. If we were actually gonna had to do some machining and lapping of the valves and which you can do- then we’re talking about remanufacturing and that’s. That’s not what we’re talking about. Yeah, it kind of sounds.

[00:33:09] More in depth when you say rebuilding when really it’s not all that big of a deal yeah.

[00:33:14] We’re just, we’re just replacing parts, yeah, yeah, internal parts, but still, well, right, right, and they’re important parts. I mean they, they’re kind of important to the operation of the of the engine and the power plant of our airplanes, but they’re not rocket science, it’s not. It’s not. It’s not terribly difficult to do if you, if you just take your time and pay attention to

[00:33:38] What you’re doing a little bit earlier you said you wanted to circle back to cooling and cowling.

[00:33:42] Oh, right, right. So sort of plays into the maintenance when, when you’re, when you’re building your airplane, or if you get a used airplane, especially an airplane that has a cowled in engine, the rule of thumb is double the exit. So what that means is, let’s say we’re talking about a, an edge airplane that has like a, like the full-size airplane, has the two open holes, one on either side of the spinner, right, like as if it had a light combing engine or something like that.

[00:34:16] So that’s your inlet, right, that’s the air that is allowed to go into the cowl to cool the engine, assuming that the engine isn’t hanging out the side of the cowl. So you want, if you to get to get real airflow and so you’re not choking up the air in there, you really need the exit to be roughly twice, if you can, as large as the intake, and usually we do that by kind of trying to cut a hole, if you will, or some sort of maybe vents or something in the cowl, such that the surface area

[00:34:52] Of those is roughly double the surface area- or lack of surface area, if you want to use that term- of the intake. That’s how you get proper cooling. You have to have more exhaust than intake. Yeah, that’s.

[00:35:03] That’s a that’s good to know and that does make sense, though, because you want to make sure that any air that gets in there can easily escape, so it can be replaced with new, cooler air, right?

[00:35:11] There. There are some folks out there that will argue that and they say: well, you want to make sure the air hangs around inside the cowl long enough for that transfer of heat energy to happen. Well, yeah, got it. But over the years that I’ve been doing this, I’ve had way better results with a lot of exit air, as opposed to choking that off and going for scale. Looks, now I do. I will admit that I do have airplanes that are that I’m cheating, but I don’t fly.

[00:35:46] Those airplanes very often and I fly them very, very rich, so I try to make up for it with extra fuel and oil. Yeah, and worst case scenarios: you just have to replace the, the bearings and stuff sooner, or the.

[00:35:58] The piston and sleeve right, which gives me. It gives me a reason to tinker with my airplanes, and that’s never a bad thing, nope. So but yeah, that’s, that’s basically. That’s basically how, how I go about rebuilding one, a two-stroke and a four-stroke. I’ll just- it’s not a lot different. I mean the, the bearings in the crankshaft, they’re, they’re sort of pressed in, just like a two-stroke, there’s all these extra little bits on the top of the cylinder but on in the case of four strokes. Well, at least with satos, the nice thing about those is:

[00:36:32] You can four screws and the whole jug comes off, which is pretty, pretty slick if you don’t want to take the valves and stuff apart or the valve train- excuse me, the os’s are a little bit better- like, usually the head comes off with the valve. Well, the head does come off with all the valves and stuff attached to it, but it’s not the whole cylinder. So you still have to go through that whole process of pulling the sleeve out and stuff like that, whereas the sato it, the jug, comes off and there you go, your piston’s right there. So I will say sato does.

[00:37:04] Make things a little bit easier on the maintenance side. But as far as, as far as rebuilding them, the process is very similar, just making sure you get those pieces back in the right order and in the right position. Well, and I guess the four strokes- I guess we do tend to, we do have a little bit more concern with the valve lash, stuff like that. So on a rebuild on a four stroke, I’ve never actually had to replace valve components, but I suppose if you did, you would have to go through that, adjusting the valve lash as you would periodically on a four stroke, that’s in.

[00:37:39] Service and you do that according to, however, the instructions that came with the engine direct you or whatever you find online, but usually when an engine is cold, you want two to five thousandths. I think it is last time I read my sato instructions, but, yeah, that’s really the only other hiccup that you that you might encounter with a four stroke over a two stroke.

[00:38:00] So is there anything else you want to cover or you think we got it all or should I say do you.

[00:38:05] Think you got it all because I didn’t do much talking well, I mean well, you talked about your, your experience with that old traxxas engine, and that doesn’t. That doesn’t count for this.

[00:38:17] It’s a two-stroke engine. Well, I guess that’s true, sure, but I mean you could put that in an airplane. I put a small prop on it, though no, I think I think that pretty much covers it. I’m, I, I’m, I’m sitting here looking at this irvine that I’m getting ready to put back together. I don’t think I’ve missed anything. If I have, hopefully somebody will, will.

[00:38:40] Call me out. You said that you could put like a, the traxxas engine in an airplane. What is the difference between now like, what is the difference between an rc airplane engine and like an rc car engine? I mean, I know they’re, they’re close and one has a starter that you don’t have, obviously, like on an airplane, but what’s the difference? Car engines are designed to run in an

[00:39:01] Entirely different environment. They’re designed for high rpm, so the porting is different. They’re designed to run without the assistance of a lot of air moving over them, so they generally speaking have larger heads and more pronounced fins and things like that on the crankcase and so on, and usually the carburation is quite a bit different too. On some of the larger car engines, when we get into the, into the 21s and 25s and larger, they incorporate

[00:39:34] Things like slide valve carburetors which are more responsive, which is what you want if you’re racing. So yeah, to put a to put a car engine in an airplane, it can be done, but you have to. I mean, you have to realize that they’re designed to be run at 18, 20 000 rpm as opposed to 10 to 12, so you have to prop it accordingly, okay. Well, I’m just curious that I wasn’t sure what the difference was. So, yeah, yeah, yeah, they’re. They’re just designed to run in a different environment, but they run on the same principle. Just one more thing: I mentioned the ringed engines.

[00:40:08] And I meant to have one here to remind me. But a ringed engine you really, if you’re replacing a ring on a piston, number one those rings are- are made out of a fairly high tensile, strength steel and usually they’re they’re hardened and chromoly usually, but they’re designed to not be very, very flexible. So you have to be really careful when you, when you’re stretching a new ring over a piston, don’t go too far, and then also when you’re sliding the sleeve back over that.

[00:40:40] Piston. You have to make sure very, very careful that you’re compressing that ring somehow before the sleeve slides over. Now most sleeves are tapered at the bottom, on the insert side, which means as you’re sliding the sleeve down over the piston it usually has a built-in sort of taper to help with that compressing this, the ring, as it goes into the cylinder. But that’s just one thing. You got to be careful, otherwise you’re going to be breaking that ring trying to jam it in.

[00:41:08] The in the liner, and that’s not good either. Let’s see, when I rebuilt I rebuilt an old ford motor for a mustang and on that one. When I did it, I had, well, first off a ring compression tool- when you’re putting it back in yep- and then I also had, like the, the ring expansion pliers- I guess is what you call it- that actually, yep expanded the rings out. Do they make the same thing then for?

[00:41:32] These engines or do you just kind of have to do it without that? For car engines? I’ve seen. I’ve I think I’ve seen the ring compress compressor sleeve tool thing like for rc car engines. Yeah, but rc car engines for the most part don’t use rings anymore so we don’t really have to worry about that anymore. But I don’t, I’ve never seen those types of tools for model airplane engines. Okay, I just I’m just really, really careful about when I’m sliding and I use lots of lubrication. When I’m putting an engine back together after run, oil is what I use. I just wasn’t sure if

[00:42:04] Those tools specialty tools or anything that would make it easier so yeah there would be.

[00:42:09] I mean, if they made a micro version of a of a ring expander and a compressor, that’d be awesome, but I can imagine the market for something like that would be really small. Yeah, probably may not be cost effective to produce something like that. As long as you’re careful, you can do it.

[00:42:28] Yeah, and I guess that’s the other thing too. Like with all these smaller engines, if you do have rings on them, the sizes are going to vary so much that it would be hard to try and make one that would cover from a tiny 40 size all the way up to like a 50 cc.

[00:42:43] And upwards. So right, yeah. And generally speaking, the bigger they are, the easier they are to work on and replace parts. Generally speaking, all right. Well, good deal then. Do you have anything?

[00:42:54] Else you want to cover? No, no, that pretty much. Pretty much does it. Yeah, I? I think we’ve covered everything. So until next time, I’m Ron and I’m Tom, we’ll see you later. Goodbye, we hope you.

[00:43:08] Enjoyed this episode of the RC Plane Lab podcast. For topic suggestions, to ask questions or to give anything back, connect with us at rcplanelab.com or email us direct at either Ron at rcplanelab.com or com at rcplanelab.com. You can also text us or leave us a voicemail at 818-351-9846. Please subscribe, rate and review us on your favorite podcast app. Until next time. May your landings be gentle.