Hi i had my mcd rally car out today, towards the end of the tank it just cut out like it was starving for fuel ive checked spark plug and reset coil also vented tank already. plenty of fuel in bulb......got me scratching my head ?

i would bet that it overheated and the ring seized , unbolt the topend and check the inside cylinder walls and ring , i bet that the cylinder walls will have scrape lines and the ring toasted

I refer you to both the points in my post in your thread... http://www.rcuniverse.com/forum/fb.asp?m=8104629

Hopefully it's a back pressure issue, as I had. Indeed the symptoms sound the same. Starving for fuel after half tank. Hopefully, it's not related to that filter you have, but it could be, they are not that good.

Does it run ok now that it has cooled down and has a full tank? Try running with the fuel cap 'loose', just a turn or so. Does that help? If so, it's the breathing issue.

I tried loosening fuel cap but it will still not start, spark plug is light brown in colour, its as tho its lost compression......what air filter do you recommend ?

Filter, the FG foam one with an outerwear. The HPI Baja filter is also very good.

Plug should be a dark chocolate colour, light brown is not a disaster (grey and burnt would be indicative of seriously overlean), but may indicate lean running. Have you changed the needle settings? If so, check my FAQ at the top for stock settings and try again.

Check the ring and cylinder as splcrazy said, I hope your engine is not damaged. []

Foxy, yes i have changed needles, will try what you guys suggested, thanks for your help[sm=thumbup.gif]

what oil and ratio are you running?

do not use outboard oil

you might have stuck the ring, if the bore isnt damaged just get a new piston/ring then have a buddy with a lathe take .002" off the diameter of the piston down to just above the wrist pin hole

Exhaust plugged?

Hi guys, got it started but it reved its nuts off, had to give it heaps of fuel to get going tried to get it to idle but it cut out, had to keep choking to get it going seems like its not getting enough fuel, i loosened fuel cap......might need bigger fuel tubing maybe ?

it may not be toast after all.......also set needles to factory settings

yeah man sounds like the ring is buggered , if your priming the bulb to keep the engine running sounds like its having a hard time sucking in fuel , in that case its proberly spitting fuel out the carb insted of sucking into the motor .( as you said it lost compression ) no compression means it will have a hard time sucking fuel into the motor thats why your priming the heck out of it to keep the engine running lol

Ok so it is toast !!.....il have to get a new topend then

unbolt the topend and check first to see whats happened , check the ring and piston for damage , you will maybe need a new piston and ring and clips . if the cylinder has only slight scoring lines you can still use the cylinder , but it might not run as efficient .

just stripped engine down, it has slight scoring in cylinder and has toasted the top of the piston, i even picked out a small fragment of metal

yeah if ya really want to save money you can still run the head only if that scoring isnt too deep , but its upto you if you want to just get a brand new topend . what you will need now is a new piston kit and make sure the pin clips are included , maybe buy a few more clips just incase , they are sliperylittle springy things lol and are real easy to loose . flush out the crankcase with fuel to make sure there are no more metal bits floating in the bottom case then if ya have an air compressor blast it all clean . to me it sounds like the engine ran too hot , increase the amount of oil mix you usually put in the fuel .

remember the dot or arrow on top of piston faces exhaust outlet .

Ive just ordered a new topend kit, i will flush bottom end out like you suggested and also gonna run more oil and outerwears prefilter, maybe cut rear window out for more cooling too......thanks a heap for all you guys help.[sm=thumbup.gif]