Is my motor finished??

[aclmusic]

On Tuesday I was racing my Ofna Mutilator (correctly broken in) up and down a large expanse of concrete generating very good speed for about 4 minutes, all of a sudden, the engine sounded like it was revving higher and the truck started to slow somewhat then the engine began to smoke. I think I may have been running way too lean. I checked the glow plug and it was burnt, I cleaned off the plug and added some after run oil and readjusted the needles to a richer setting. I took the truck out again running rich and the engine began smoking again and not really producing great power (could be due to the needles) Is my engine finished? I Am am new to nitro racing. Any help would be appreciated.

 

[miketroll357]

Have you tried setting the needles back to factory settings and tune from there. That would be the first thing I would try. Hope your engine is ok. Also put in a new glow plug. If it is black it is shot.

 

[beason]

where is the smoke coming from? you could have a broken exhaust coupler, or the head could have worked loose.

 

[jon2]

Did you set the needles prior to running it?

When you say "correctly broken in" ...what do you mean?

 

[aclmusic]

Thanks for the responses. There was smoke coming from the head. As for the needles the truck was purchased used and had 1/2 gallon of fuel through it already. The needles were set but I started to tweak the low speed needle along with some throttle settings to adjust to my FM transmitter. I really think it was my fault because when I ran the truck prior to the adjustments it was fine. The previous owner followed the factory directions for motor break-in.
Thanks, I will replace the plug. I will check the head end the exhaust coupler too. I saw some moisture around the coupler during the second run too.

 

[FastEddy]

Turn the engine over by hand and see if there is any compression. if none or very little you most likely have a toasted engine.

FYI.
In RC speak, a motor uses electricity, an engine uses fuel.

 

[aclmusic]

My bad about the motor/engine thing I know better. How exactly do you do that? I'll tell you this much, the roto start was spinning very easily prior to startup on the last run. Is it possible to rebuild it?

 

[FastEddy]

The best way is to remove the engine and turn the flywheel by hand. You should get a good POP out of it. If it turns to easily or no POP its worth taking the head off and looking at it.

Rebuild kits are available but usually not much difference in price from a new mill.

 

[aclmusic]

Thanks for all the help gents.

 

[aclmusic]

OK the engine seems fine but I think I found the problem, the rear diff is not working properly causing the engine to spin to high heaven possibly creating the high temps. The rear wheels are not turning when I turn the rear shaft, I will see when I take the diff apart. I guess I have been officially inducted into nitro world.

 

[Rolex]

You're learning the hard way, just like the rest of us. The more you break, the more you learn and the sooner you can give the next guy some advise.

 

[aclmusic]

Well after I fixed the rear diff issue (the shaft set screw was just loose) I went to start the engine as I was turning the the engine over with the roto start I saw fluid (after run oil and fuel I guess) spraying lightly from the rear of the engine; it sounded like it was on the verge of starting but it never did. Could someone diagnose this one? Any thoughts would be helpful. It is a Ofna force .32

 

[Plaidfish]

first thing to do if it's a used rig is NUT AND BOLT THAT BEOTCH!!!!
yes tear every part of it down to screws and rebuild it....most hobby guys do it to a brand new RC before it's even had fuel through it....and we do it especially to a used RC.....you may very well have inherited a proverbial turd if you didn't know the owner as a friend.....but enough negativity....seriously, if you have any mechanical skill you would do yourself a huge favor by doing a complete rebuild...one you can use oil instead of grease in the diffs and loctite on all the screws into metal (like the set screw you just found loose, hope you put loc-tite on it).....the stuff leaking from the back is another issue, air leak.....shouldn't have ANY on your mill....air creeping back into the piston is like running real lean, only with a leak it's inconsistent....smoke coming from the head is not a real good sign either.....get yourself a temp gun too.....just as a benchmark while you're learning so you don't really cook your mill......also try a new plug after you fix the leak (use high temp RTV seal on all your mills seals (carb throat / exhaust port / head / rear crank plate)....again even brand new mills get this treatment from most of the guys here......point is just because it's new don't assume it's perfect....if you really want to run that sucker, learn your RC by memory so field repairs can be done quickly and have at it.....

 

[aclmusic]

Thanks for the tips. I guess the fact that it is a RTR gives me more reason to do a rebuild. The truck was great when I recieved it. I started messing with settings and that's when I had the problems. I'm going to work on that engine like you said too.

Thanks again.