86r cutting out at wide open throttle?

[dirtbike77]

today we went riding with a bunch of guys... when everyone decided to race... well it was two banshees, two 4ooex's, and a atk260 dirtbike.. well any how when we were racing it ran fine , but when i really gunned it in 6th it was catching and catching speed, but all of a sudden it starts cutting out, and it kinda bogged out but then at this point while still cruising it ran pretty good? what could it be?

[200x Basket]

well you are running out of gas, spark, or compression. it really could be any of that.

[dirtbike77]

it only did it when we were wide open throttle... but other then that i could wheelie, do anything else. it just mainly tryin to race wide open throttle.... another thing is the engine is bored.80, witha head shaved on it... i use regular gas.... could this be a problem?

[YTZ250N]

You could try to bump up the main jet one or two and see what that does.

[samster143]

Could be runnin' lean at high rpm. I agree with YZ250N. Try a bigger main jet.

[Mike Fort Laud]

80 over plus a shaved head for higher compression,running auto gas and it only does it at Wide Open Throttle. Here we go with the IT COULD BE'S......It could be that you are using low octaine auto fuel and with the higher compression you may need a higher octaine fuel. It could be that the motor is getting hot when you are holding it wide open and Pre-Detonation is occuring...Check the cooling system.... It could be that you have a spark plug that is misfiring or breaking up.... The 250R's are also bad about the plug cap going bad...mine did. Bad coil,but I doubt it. What type oil are you using and what are you mixing it at????Try high octaine fuel with a new cooler heat range plug with the engine cooling system checked. That is the cheapestt and easiest.

[TimSr]

Does it die instantly when you hit wide open, or is it after its running fine wide open for several seconds that it will suddenly bog down like its out of gas? If it does the latter, its probably just floats set too low.

[dirtbike77]

but then after that few seconds it starts to break up a bit, like its gonna cut of, its bogs down but then when i let of at a steady cruise it'll ride fine... but it'lll ride fine 1st through 6th? its just when i hold it wide open...

these are the things done to it
1 .80 over
2. head shaved
3. fmf fatty pipe
4. boyessen intake manifold
5. mixed at 32:1, (using super techniplate) (regular fuel)
6. stock main jet...(148)

[250rAL]

OK you've got a pipe and higher compression and you're still at the stock jetting? You're lucky you haven't melted it down already. I've got an FMF but without the higher compression.I've got a 36mm carb and I'm running a 172 main.

[dirtbike77]

any more suggestions to make this bike faster?

[dirtbike77]

what other wire harness can i use for this bike? or were can i find a wire harness from..

[Mike Fort Laud]

Adding a pipe you should jet up, but having a higher compression ratio would not need a bigger jet because all you are doing is compressing the fuel and air more. Anyway if you want to make it 5-8 MPH faster change the sprockets to a different gearting ratio. Stock sprockets are 13 teeth front and 39 teeth rear. For a faster bike on top end go to 14 front 36 rear. Even faster is 15/33 but you don't have the power to pull 15/33 gears. On my '85 250R I run 14/36 but I like top end. To be a quicker bike racing a short distence or on the track you would gear the sprockets the other way. But you will lose the top end speed,but be quicker off the line.

[dirtbike77]

what kinda power imgonna need to pull that 15/33 ratio? where can i get the 33 rear sprocket from?

[Mike Fort Laud]

I bought my rear 36 tooth aluminum sprocket from my local ATV fix it shop. But it is made by Sprocket Specialists and can be ordered by anybody. Chaparral sells Sprocket Specialists. Your bike would work with 15/33 but would probably take a mile to wind out 6th gear. I would not recommend putting that gearing on the bike. 15/33 is for big time motor work or 310 kits. Stuff like that.

[dirtbike77]

do u have the airbox lid on or do u have the airbox lid of? does it make a diffrence?

[Mike Fort Laud]

air box lid off.. But I also have a K&N Filter with an Outerwear on it. Carb jetted heavy.....

[dirtbike77]

will there be a noticeable diffrence from the stock gearing of 13/39