Engine. Problems, problems...

[Dandare]

I have an 8th .25 engine which is new, i have run 5 tanks through it, the last race evening it was still set rich for 2 heats then just before the finals the pull start snapped (5th one overall, lol)

Now, i've bought an SMD starter box, set it up fine. I've removed the pull start from the engine but used the plastic housing to cover things up as i don't yet have a backplate.

Here's where things go wrong. When i started the engine on the box in my garage the engine suddenly raced but, the throttle slider was in the idling position ie, 1mm or so gap. i had to close it down pronto before it done any damage. At this point i didn't have the electrics on, i just manually operated the throttle. This happened yesterday.

Today i try again, same thing, though when it fired, the idle was eratic then it raced so i had to shut it off, again, the throttle was either on idle or very near so.

I now don't know what to do, all needle settings are as per the last race evening where it ran 2 heats fine.

Is there something i'm missing when converting from pull start to a box or has some dirt miraculously got into the carb inbetween use? I don't know.

I've had such rotten luck with these damn things lately it makes me want to race 10th electric, lol.

Any suugestions welcome.

Dan.

[mark christopher]

put the back plate back on, it seals the crank case

[Dandare]

I don't have a backplate at the moment. The one way bearing on my other engine slides onto the crank & locates into the pullstart, on this one there is no visible one way bearing but a nut/shaft (one piece of metal) & the nut end locates onto the pullstart & the shaft slides into a hole (the crank?) but you can't actually see a one way bearing. Maybe removing this shaft has caused the problem ?

[racingdwarf]

is the pull start still fitted as if you were going to use it? so it is the back plate?

Nitrotec......Nitrotec......Nitrotec

[mark christopher]

Originally Posted by Dandare

I don't have a backplate at the moment. The one way bearing on my other engine slides onto the crank & locates into the pullstart, on this one there is no visible one way bearing but a nut/shaft (one piece of metal) & the nut end locates onto the pullstart & the shaft slides into a hole (the crank?) but you can't actually see a one way bearing. Maybe removing this shaft has caused the problem ?

rebuild it as it was, you have removed somthing to make an air leak.
the engine will still work on a starter box with a pull start installed

[Dandare]

You are both right !

Took the engine off & peered into the hole where that shaft was located to see.... the conrod staring back at me, lol.

I guess air coming in from the above 'void' was making it run massively lean (& hot very quickly!) ? I think it all makes sense now

I nearly threw that pull start away too, glad i bagged it up now !

Well i've put it back on, minus the coil & string, gave it another go & it both started & ran as sweet as

(Dave, i hear where you're coming from, lol. Next time i'll invest wisely...)

Cheers chaps.

(ps, i think had i done the same with my other engines i wouldn't have had the same problem as removing the one way bearing & pull start mechanism wouldn't leave a gap as the bearing just slides directly off the crank)