300 fourtrax help!!!

[jcs327]

I have an 88 300 fourtrax 4x4. problem is, it bogs after 1/8 throttle. cleaned carb, new air filter. stock settings-120 main, 40 pilot, 2 turns out on air screw. everything is clean and tight. needle clip is in 3rd position right now but I have had it in every position and the bog is still there. It does idle fine. It will not accelerate when rolled on smooth, but will when the throttle is pumped, it will gradually increase rpms when it is pumped. airbox lid is on. its getting plenty of fuel. I have done everything I know to do to the carb. could it be an exhaust valve problem, or possibly a problem with the exhaust system itself? thanks in advance.

[bwamos]

Being that it is an 88.. it is very likley that the carbs o-ring deals have hardened, and it's allowing air to get sucked in causing you to run very lean. I'd check there.. then check to make sure the intake boot on the motor isn't leaking.

After that, I'd check your cam timing and your spark (may not be a full spark should be blue not yellow).

[jcs327]

thanks. I checked the carb o rings. it runs fine at idle. I will look at replacing the intake boot.

[krt400ex]

Your compression is probably low. I would re-build it. That will probably solve your problem.

[jcs327]

it will accelerate well if you pump the throttle, then when it picks up rpm's it runs great. the prob is when you roll the throttle on without pumping it it bogs, like not getting enough fuel. have checked everything from fuel petcock to jetting and still ????????