2006 yfz help weird problem

[yfzrider619]

i have a 2006 yfz450 ive had it for about 2 years and i have ran the same jetting as always 165 main and 45 pilot. i have a tc exhaust and a k@n pro flow kit. i even had a high comp piston in it and ran the same jetting, it ran fine, but last summer my oil pump blew causing my motor to completly seize up, that was when i had the high comp piston in it. i got the whole motor rebuilt and put back together, but now its running really weird, at cruising speed it spits and spudders, and when im really putting it seems likes it choking out on fuel or loading up, and it sometimes stalls out of no where. also backfires alot when i let off the gas. plz any help would be appreciated.Thanks

[chadbarger18]

it sounds lean if its backfiring but thats about all i know about jetting

[Ride1Rob]

I'm thinking you're running too rich. Maybe your fuel/air screw needs to be readjusted. It's something to do with your jetting. I think that you need to come down on your pilot to a 42, change your main to a 162, and see how that changes it. If it gets a tad better go down on your main another size. When I had a HC piston in my bike I was running a 178 main and 45 pilot. Got rid of the HC and went back to the stock piston and had to go to a 160 main and down to a 40 pilot for it run right.

[yfzrider619]

it just seems weird though i even ran the same jetting before i had the high comp piston and i ran the same when i had it in, do u think my bike got used to the high comp piston and now that i dont have it, its running weird?

[Ride1Rob]

What else have you done to the bike. Pipe, intake, cams, etc...

[yfzrider619]

a tc exhaust and a k@n pro flow kit . ive ran the same jetting same everything throughout the whole 2 years ive had it and it ran fine. but since my motor blew up and i got it rebuilt its running messed up

[yfzrider619]

figured out the problem guys, air/fuel screw needed adjusted. it was a few turns out of wack. Thx for the help.

[Ride1Rob]

Told ya ;) . Glad you figured it out