OS Max 35 w/loose con rod - any good?

If you have other identical engines, save it to build cowls around -- balsa dust and drips of epoxy don't hurt engines that are already dead.

Otherwise, it's probably more expensive to rebuild than to replace.

I like your idea of using it as a template for other engines. Also you could keep your eye on ebay for another one like it to come around. A friend gave me a strange OS 40 FP years ago that had been internally modified and then run to death. It also looked as if it had spent a long time under water. I asked the folks at the flying field if anybody had a dead 40 FP, and somebody came up with an engine that had suffered a cracked crankcase in a crash before it was broken in. I put the parts of the two engines together and ended up with a very nice engine for free.

I'll have to keep my eyes open. It's an odd engine - the intake is part of the casting, not attached like all of my other OS engines are. I'll take a picture of it tonight and post it here. I bought it off of eBay, and the seller was quite deceptive in his description of it. He had to know the engine was shot - the glowplug was missing the gasket, was only hand tight, and was burned out. The back plate screws were finger tight, and the prop drive plate was gone. Someone wore it out and stripped it, and sold the carcass. At least I didn't pay that much for it. I'm not sure if the connecting rod only is loose, or if the crank itself is worn, so it's hard to say what it would take to get it running again.

Lesson to be learned - Let The Buyer Beware. I just noticed that the mixture screw is broken off. The glow plug is burned out, the prop drive washer is missing, the connecting rod is very loose. I should have become suspicious when I saw the prop drive plate was removed. The person that sold this engine should hang their head in shame for selling a worthless carcass. And I should hang my head in shame for wasting $15 on it without realizing that something was not right.

$15 is a cheap lesson. And you should be glad that you have found a great forum where you can ask for advice from a bunch of very helpful people who have a lot of experience with engines.

Just out of curiosity, when you bought this OS 35 were you looking for a cool engine to use on an unknown future airplane, or did you have a specific airplane in mind? Those old OS engines are kind of nifty because while they are somewhat low tech by today's standards, a lot of them still run well and are capable of hauling a plane around nicely. Also, I have heard that engines made 30 or 40 years ago were designed for larger props and lower RPM, which is the way I like to fly.

Anyway, don't rule out the possibility of making lemonade out of this lemon. You may still be able to come up with parts for it. If I remember correctly, this forum is where I found the wreck that turned my useless worn out junker into a good engine. Just put it away in a drawer and keep your eye on ebay, and post a "wanted" notice on the RC forums once in a while.

I am :). This forum is invaluable.

I already had a couple of them, and was wanting a few more for spare parts or more working engines. The booklet for them says to use a 9x6, 10x5, or

10x6 prop on them.

Yeah, all it really needs is a connecting rod and prop drive screw. OS stuff goes on eBay all the time, so this engine may yet run again.

"Ook" wrote

10 x 6 would be way too much prop, IMHO.

I have a lot of old engine parts in an old cookie tin. This lot was part of the large collection I bought from Vince Miller a few years ago. There are rods, drive washers, heads and a few pistons, among other things. I have no idea what most of these parts belong to. I have been thinking of selling them on ebay, on the off chance that somebody might want to buy them. Let me know if you're interested. I can send you a photo of the stuff if you want.

Yeah, I'd certainly be interested in a rod and drive washer for an OS Max

1. The only big engines I have are OS Max 35s, so only parts for that engine would be of any value to me. Any idea if any of your stuff fits that engine?

I dug through it a while ago, and I don't think there's anything for an OS 35 in there....

Waahhh....sometimes I think I'd be better off if I just bit the bullet and bought a brand new engine or two instead of playing with these antiques. I guess I'm old fashioned. I like to build with balsa, I cover my wings with silkspan, and I run without a muffler. And I fly control line. And I BBQ with charcoal....

It all depends on what your favorite hobby is. Model airplaning is made up of several different hobbies. There's flying RC, flying control line, building from balsa, scale finishing, tinkering with engines, finding the right combination of motors, propellers and batteries for a particular plane, and of course repairing crash damage. You can choose any or all of them. I like building from plans and flying just enough to see my creation in the air for a while, then I go on to the next project. I don't care much for scale detail, though. And I try not to crash because I just don't like repairing already-flown planes for some reason. For me, it's 70% building and 30% flying, and no electric motors!

I used to fly a lot of Cox 049 powered planes because I figured out how to run these engines reliably, and because they don't break when they hit the ground. To have a good time with a Cox Black Widow 049 it's a good idea to have new glow heads and new reed valves on hand. But ever since these items went up so drastically in price I haven't been as enthusiastic about it. Also, ever since I mastered the art of touch and go landings I have had a preference for .10 to 91 sized airplanes with throttled engines. I don't know exactly when it happened, but I also got kind of spoiled by flights longer than 4 minutes.

Anyway, the point is that you don't really have to follow any rules, including your own. Just try different things and see what trips your trigger. I'm kind of like you in a way. I don't get into all of the new stuff. I like non computer radios because I think the computer takes some of the fun out of it. I don't care for new engines, I have a drawer full of OS 4 stroke and OS FP 2 stroke engines from the 1980s and

90s. In fact, I counted the other day and discovered that I have around 50 old engines. I finally ventured out a bit and bought an old SuperTigre 29 to put on a New Era 20 sized pattern plane I've been wanting to build, because the 25 FP wouldn't be enough for it.

If you like old non throttled, non muffled engines, maybe you could find an internet group full of guys who know a little bit more about them and could help you find good ones. You might also try picking up an old OS FP 15 or 20 just to see if it introduces you to some enjoyable aspect of model airplanes that the old non throttled engines could not. This is what happened to me after I learned to fly with a Cox engine and then I built something with a throttle.

Come to think of it, I have just the project for an old fashioned guy like you. Check out this plan:

is a 2/3 scale rendition of the legendary 6 foot Buzzard Bombshell from the days of freeflight competition in the 1930s. Get a .10 sized Magnum, Thunder Tiger or OS engine from ebay and a radio with three mini servos, and build the plane as light as possible. You'll have more easy-flying old fashioned fun than you could imagine, combined with the reliability of a modern radio and engine. Just don't be tempted to put a Cox 09 on it because you'll miss the point because it needs a throttle. I've built two of these, and you just can't beat it. It will fly for almost an hour between idle and 1/4 throttle on two ounces of fuel. What an airplane! If you find that you miss the old fashioned equipment, you can always go back to it. (I still have a few of my old Cox engines!)

I just remembered that I actually built 3 Baby Buzzards over the years. The first one had an OS 15, which was overkill. The next one was powered by a Thunder Tiger 10, a very nice little engine. I sold that plane, but I just had to build another one eventually. It had an OS 10 FP. I wouldn't want any more or less engine on one of these.

It's definitely earlier. The intake is part of the casting instead of a seperate piece like the later ones are. I'll see if I can get the specs on the rod.