1/8 nitro buggy cuts out?

[james1976]

Hi all, hope someone can help with my problem, I have a hyper 8 buggy with a nosram RS28 evo monster engine, all is fitted and running relatively well, starts like a dream and also runs like a dream to an extent, I have done my high end which is perfect revs high with no low spots and more than enough smoke from the exhaust,bottom end to me seems fine also, but I assume there must be something wrong with this....... i set my high end then low end, done the pinch test on the low end and seems perfect revs high then low and cuts out within 5 seconds, i just need some advice on to why when i give it a good run, have a thrash about as you do, it just cuts out??? i don't apply brakes and then it cuts out, which i could understand because that would mean my idle would be too low and that would make sense, but its not that, when apply brakes there is still a 1mm gap, it just happens at random only when I'm free rolling though mostly, so no throttle or brake?? anyone have any ideas????? any constructive input would be a geat help, thanks in advance.

 

[olds97_lss]

I've had that when engines are well worn. No other symptoms but flame outs for no reason. When I took the engine apart, I could push the piston through the top of the sleeve when cold. Not all the way through, but enough to have 2-3mm of piston sticking out of the sleeve.

Sent it in for a pinch and the flameouts went away.

How old is your fuel? Really old? Have you tried a new glow plug? Couple things to rule out unless you want to try just tearing the engine down and seeing how the pinch is. If it does what the bottom two do on this, then your pinch is bad causing blow by which could be causing the flameouts like mine:

 

[james1976]

Thanks for your advice mate, that might shed a lot more light on my problem, I really don't fancy stripping the engine down unless its a last resort, my fuel wasn't old, but it was left in the garage for say 2 weeks max so could have got damp I suppose, I'm going to try a new glow plug and fuel, maybe its he fuel I'm using I was using 25%? do you think that's too much? can't see why though as long as its tuned to that fuel shouldn't be a problem? anyway I'm going to try a new plug and might go down to say 20% or even 15% fuel, thanks for your advice, not scratching my head so much now, cheers

 

[olds97_lss]

25% should be fine. That's what I run in all my engines.

 

[james1976]

Yeah I thought 25% should be fine, i gues i can check the pinch just by taking the cooling head off and the removing the glow plug cap and turning the flywheel to see where the piston sits? thanks for your time really appreciated I will keep you posted on how I go, thanks again, james.

 

[olds97_lss]

That probably won't help you much as the conrod shouldn't be stretched enough to see the pinch point. You have to disconnect from the crank and push it up manually to see how far up the piston goes.