The car is a Kyosho inferno 7.5 sports RTR. Stock engine.

When i fireup the engine it starts going backwards ! If i hit the throttle, the car die. But if i let the car go warm, about 70-80 degrees Celsius, then hit the throttle, the engine makes a loud bang noise, and the starts to go the right way.
It have never happened before, but now it suddenly is doing this everytime i start it.

This cant be very good right ?
Anyone know whats making my engine do this, or what i should do to solve it ?
I have changed piston and sleeve at the start of this summer if that has anything to do with it.
Running at 15% nitro, stock glowplug.

Does the car perform better if i change the glow plug ?
Which plug should i use ? Anyone have a clue ?
And what is the maximum engine temperature ?

Thx in advance // Ivah =)

I think you put the sleeve or piston in wrong when you rebuilt it. By doing that, you made the ports deliver fuel in the wrong order, making the fuel detonate/explode too early, which makes the piston go the wrong way.

When it warms up, the timing must change just enough for it to fire somehwat correctly.

The bang is probably SEVERE detonation when the piston slams into the other direction. Makes sense.


You are destroying your engine....and the rod might be shot -- maybe the piston, too.

Reconfigure the sleeve AND the piston, because they are in the wrong way. The sleeve ports and piston skirt must be in the right position.

Are you 100 % positive the engine is spinning in the reverse direction? Make certain the flywheel is spinning backwards. Lift the car up and see if the wheels rotate in the reverse direction.

In order for this to happen your engine can not be a pull-start or roto start. It must be started by a starter box or possibly drill started without the use of a one-way bearing on a starter shaft.

Possible causes are, starter box spinning in the wrong direction.
using extremely short bursts while cranking the engine over with a starter box.

Since I highly doubt your engine is running backwards(although I have started OB boat engine backwards) I would check the flywheel and ensure it is secure.

Most sleeves can only be fitted one way only, by a key. No matter which way the sleeve is in will not cause fuel to enter any earlier than it would normally enter, as the exhaust port is always higher than the boost and side ports. Also, ignition is controlled by compression with heat not when the fuel enters the cylinder.

Ryan

the stock 21 engine in the inferno rtr does not have a key as i found out when fixing my friends buggy. I would put the sleeve in and put the cooling head on and when i would move the head for the screw holes the sleeve would move and be in the wrong area. I think the sleeve might of moved a bit when u put the head back on. have a quick look through the exaust port and see if the sleeve port is alligned correctly. and if not sure definately take it back apart and try and get it right. Make sure it is right cause u do nit want to damage or kill your engien.

I have putted the car on a box when i started it, and the wheels are spinning in the wrong direction !
The thing is i have driven the car lots before this started to happen. And it IS a pull starter [&:]
Think its very strange that it has started to happen so suddenly.
I have taken apart the engine now, and the sleeve is in what must be the right position. The only port big enough for exhaust, is in the position for the exhaust. [&:]
I did take it apart before i checked this so i didnt check the exhaust port when i took it apart. It could have been a little wrong i guess.

About the pull starter, it actually started to go the wrong way last season. Dont know what happened, but i had to dismount the pull start and change the direction of the thingie inside there so it started to go the right way again. Think the pull starter is the bad guy here somehow ?


And thx for all the help, i appreciate it !

Ok, that explains the big bang. Everytime you here that bang the one-way bearing inside the pull start goes from
inproperly working (slipping)
to slamming in to the one-way, reversing direction and working properly.

It has nothing to do with installing the sleeve incorrectly.

I would assume this one-way bearing is shot, as the engine should never be allowed to reverse direction. If the one-way worked correctly when the engine is running backwards it would have quit immediately or blew your pull-start up immediately.

Possible Solutions:
When starting the engine, crank it over faster and slightly longer
Raise the idle
Check and make certain the flywheel is secure/tight
Inspect the one-way bearing for damage. It should not spin in the reverse direction!

Good luck,
Ryan

I checked my engine first, took everything apart and reassembled the whole thing again. Didn't see anything strange. Then i tried it out, the engine started normally this time but now the pulling cord got stuck ! I couldn't pull the engine around at all. At first it thought it (don't know the word, but when the sleeve gets to tight by the heat so the cylinder cant move). But i didn't drive the car hard at all, just rolled around on the street outside my house. So the engine wouldn't move at all when i pulled the starter. Then i twisted the flywheel, and then i could pull the damn starter again. But after a few pulls it jammed. Just need to twist the flywheel a bit again, and the i was free to pull. I now realized that something was wrong with the pull start, i dismounted it and checked it out. Didn't see anything strange, the i looked closer on the bearing and on one place it seemed quite worn. Im going to get a replacer tomorrow. im just hoping this will be the end of all this =)

Thx so much for the help guys, really appreciate it !

Hope it works out, good luck

Ryan