Hey guys I just recently purchased a 98 yz250 it runs decent but is a little boggish getting to mid range. This kid I bought it from had said the previous owner removed the power valve for "better low end torque" this is something I've never herd of and was wondering if its even possible. He also claim he replaced the main jet on the keihin pwm carb, causing plug fouls. When I looked it was a #175. Is this proper jetting? If anybody can shine some light on my situation it would be appreciated.
250 Power valve removed?
I would inspect the bike fully and tell us what you find.
I had an 84 and an 86 yz-125, I know with out the power valve your port heights wont be adjusted for low-mid-upper power out puts. I know if that apple core valve is out of adjustment or incorrectly installed it could cause a piston strike, No Bueno! My 2 red devils also have power valves, and one had em' missing, that bike ran bad. I re installed em' and no more bad running issues. Try to keep it factory stock unless you are a performance bike mech.....