Hi all! I'm having some problems with my engine after having a bit of a crash... The engine still starts as well as it used to, but I can't get it to rev as highly as it used to. I used to be able to get about 11,500 out of it and now only about 9,500 or so (thats a guess as i dont have the tools to measure it). Also it seems impossible to get the perfect mixture.. It used to be easy to fine tune the mixture and there was a very obvious point where the mixture was perfect and the engine revved nicely. but now when i adjust the mixture I dont seem to be able to reach that optimum point. it kind of goes from really sluggish and wet, to working ok but not brilliantly, and then the performance stays the same for about 5 clicks, and then suddenly becomes to dry and conks out. I'm not sure whether this is due to a bent needle or if the engine simply wont rev past about 9500 due to some damage elsewhere, but I've removed the needle and inspected it and there is no obvious damage at all. What can commonly cause a problem like this? The plane did suffer a reasonably serious crash, but it seems odd that it starts and runs smoothly, just that it refuses to run at the speed that it used to... Any ideas at all would be very much appreciated... By the way it's an SC 46 2-stroke.

Thanks guys!

Mike

It could be any number of things after a serious crash. Did the carb get a lot of dirt in it because of the crash? If so, how did you clean it out? Did you turn the engine over after he crash?

I would start with making sure the carb isnt dirty. My next guess would be an air leak somewhere because of the crash. Does the engine rev or run smoothly? Really need a little more info to try and narrow it down.

hi gringo, thanks for the reply! it runs relatively smoothly although sometimes when left at full throttle for a while it starts to struggle. im not sure if i got much dirt in the carb but its perfectly possible... if so how would you recommend i clean it out? i turned over the engine immediately after the crash and it turned over with no problems. ive run the engine through several tanks of fuel since the crash in the hope that it might clear it out and start to run a bit more nicely but no luck so far. at idle it seems to be quite smooth.. the throttle response is also a bit more sluggish than it was. i could just get a new engine but i just thought it might be something that could be fixed without too much trouble. whats the best way to clean it out?

mike

First of all, after a crash never turn the engine over by hand. Any gunk that got inside in the crash will do a number on the engine.

After a crash, take the carb off and flush it out. Thats what I would try first on your engine even now. Do you have a flying buddy with the same engine? Try swapping out carbs and see if your engine runs differently.

Dont give up on the engine. I would start with the carb and then go from there.

Have you checked the crankcase for any damage? Are there any visible cracks or bent portions.

Have you checked out other potential problems? Maybe it has nothing to do with the crash. Have you tried changing the glow plug, fuel tubing, tried a different can of fuel? Dont just assume its from the crash.

I was going to ask about the fuel actually. I'm currently using Duraglow 5% fuel (http://www.tayracers.co.uk/duraglow-...lon-1008-p.asp) and was thinking that maybe a richer fuel might work better... but i dont really know much about the different kinds you can get and what would be safest and best to use in my engine. I'll definately check the carb to see if i can see any dirt or gunk in there. I havn't had a thorough look for any damage to the crankcase but I havn't noticed anything. Could it be something simple like the manifold paper being in need of replacing? I could try replacing that perhaps but there doesnt seem to be any problem with fuel pressure and it is being pumped down the fuel line as it should be.

Anyway, thanks alot for your help and ill try the things that you have suggested and let you know how I get on

Mike

I am not sure what you mean by the manifold paper. Do you mean the gasket on the muffler or the seal between the carb and engine maybe? As far as muffler gaskets, I never put those on and use rtv in its place. That shouldnt make any difference one way or the other. However, if you dont have an tight seal between the carb and case that could be a problem.

You wont necessarily see dirt in the carb. Wash it with some fuel. Then get a syringe and attach a piece of fuel tubing to it. Attach where the fuel tubing attaches to the carb and blow it out several times.

If the engine ran fine on that fuel before it should run fine on it now. I was wondering if maybe the can you are using has gone bad. Like it was left open or in the sun, etc.

There are a lot of things it could be. You just need to start with the simpliest things first and one by one eliminate potential problems.

Just A passing thought but if you have A service center for glow engines close by maybe you should have your engine checked for A bent crank shaft or connecting rod??
Just A thought.

Hello Foylee
Are you using the same propeller and glow plug as before the crash?

yeah im still using the same glow plug and prop... might try replacing the plug though. im going to have a look at it today and see if i can clean it up a bit... ill let you know how i get on! thanks alot for the replies

mike

I ALWAYS completely dissasemble an engine after a crash & clean it thoroughly with fuel. I'm betting you either have a gasket leak or a tiny piece of dirt in the carb assembly. Also, you should always replace a prop that's had ANY strike damage.