Hi Guys,

Though I've had some experience with model engines from some nitro trucks, I'd like to hear your advice before I take apart my engine to repaair it.

A couple of weeks ago I had my first bad crash , a strong wind took my plane into a phone line and then it nose-crashed. Though the spinner (among other parts) was completely destroyed, the engine seemed to be ok, I cheked it carefully and had my instructor checking it as well, and besides some minor scratches in the heat sink, he aggreed it was ok. Once I got my SuperStar fixed I took it to the field to try again and it performed great, but in the second flight the engine stopped midair, my instructor glided it down to a nice touchdown but once in the ground it was hard to start the engine, when I could start it, I ran it half-throtle and it shaked and stopped again, I tried 2 or 3 more times but the engine won't stay running for more than one minute, even at half or 3/4 throtle. I thought it could be flooded so I left it rest, but then I saw oil drops hanging in the bottom of the engine, apparently comming out from the crankshaft output, what do U think?? would that be a bent crankshaft caused by the nose crash?? or maybe something else could be happening? I also noticed no wear in the crankshatf output when I move it right and left, but I did notice a small movement when i pull the propeller back and forth... not sure if that's normal though... I'll appreciate any advice or idea on what to check that you guys can give me before I try to fix my engine or replace it by a new one,

Thanks and see you!

by the way, my engine is an OS 40LA, think it doesn't have ball bearings in the output... it has only 5 or 6 flights on it

I have an OS .46 LA myself and have taken it apart several times. Meanly everytim I had a crash when hitting dirt (from the fields around us) and the carb was full of mud/sand/dust, I would just take the whole thing apart to inspect and the clean out any dirt inside.

The LA series are very easy to take apart & put back together, so don't worry there.

There everything apart, clean everything very thoroughly (I use water & soap to remove the oil etc.) Then useing some paper towels, I make sure all parts are dry.

Then, inspect every part carefully (you now have the change sice they are all clean), especially check the crankshaft for bends (roll it left/right across the edge of a table and see if it "wobbles")

Also check the housing for any cracks.

There shouldn't be any excesive forward-afterward movements on the cranckshaft especially not with a prop mounted. When the prop is removed, there can be some movement, about 0,07 inch I guess, but surtenly not more.

Also, inspect the piston for scratches, especially if there was dirt inside. Your crash may have caused dirt to go inside the carb, and while running the first time after the crash it may have damaged the piston, making it run bad afterwards. Compression would suffer, and friction would go up because of these scratches.

If any part has visual damage, replace it with a new before reassembling the engine.

You're right about the LA's don't having any Ball Bearings.


P.S Took my OS.46LA apart 4 or 5 times using the method described above, and after 3 seasons it is still working good & reliable.

P.S. Don't forget to pour some oil inside the engine after reassembly, or beter, start it u and have it run for a few minutes. This way, any moisture left on the part will evaporate, and all internal part will become protected with some grease/oil, so thing don't start to rust

Thanks a lot Dazzler_be,

This explanation makes a lot of sense to me, I was just thinking about the crankshaft but didn't think about the dirt on the ground that could scratch the engine. I've fixed some smaller engines so I think I won't have problems with this one, the only problem is that my local hobby shop is out of fixing parts for my engine so I'll have to buy at tower or something like that (which is not a problem except because I live in Costa Rica and the parts will get here in 2 weeks or so!)

Anyway, I'll take your advice and will check everything for wear... seems like an "overhaul" is waiting!

Thanks again for your help! I'll keep U posted

You should always oil engine parts before putting them back together. Starting up an engine that was put together "dry" sounds like a good way to grind the heck of the internals in the short period before the fuel gets there.

I use Automatic Transmission Oil for engine rebuilds and after-run. There are lots of other good options out there, some likely better than the ATF I use.

As for what's wrong with your engine, dirt in the carb is a good guess. It doesn't take much dirt in there to really mess with things. Espeically check the airbleed hole on the front of hte carb. A bit of dirt in there will really mess with low-end running, and it's right up front, perfect for dirt to get in to.

Oh, a small amount of "end play" is normal for many engines. Just be careful that if you push on the prop shaft and turn, you don't feel resistance or hear anything. Sometimes it's possible for the crank to rub the backplate. It's not a problem when the engine is running with a normal prop, as it will be pulled forwards, but you can shave off bits if you crank away with an electric starter. Pusher props are right out.

Be careful using water and soap, it could rust the engine.

I was assuming you wouldn't remove all the oil then let it sit around that way. Whenever I remove the oil from an engine part, I always do what I need to do, then re-oil it promptly.

Hey Guys,

tanks a lot for all your advices! I'll get to fix or replace my engine ASAP, I'll keep you posted on my progress, really thanks a lot for taking the time, I've got lots of good material to try and fix it

Cuando quieras