Jetting issues...

[motomike388]

ok i have a 02 yz 250f which i had a white brothers R4 exhaust on it and when i put it on i put a bigger main jet which was a 180 stock is 178.... I scrapped that exhaust and i put a yoshimura stainless slip on exhaust and i also put on a power now carb thingy and then i dropped back down to a 178 main jet ... The power now directions say it will cause the bike to run a tad bit rich ... So now my bike runs awsome but theres some back fire happening. My spark plugs looks good but should go down to a 175 main jet or change the clip on the needle? Thanks Mike #388

[thump353]

richen up your fuel mixture by turning in the air/fuel mixture screw on the bottom front of the carb (if you look at the bottom of the carb it's the only screw that's a flathead in the recessed part of the carb) start by turning the screw in (like your tightening it) 1/4 of a turn. if it still backfires, turn it in another 1/4 turn. if you look thru the jetting forum you will find a lot of help with this issue. also to make things easier for your self, get a zip ty fuel screw or storm racing fuel screw. it will make this adjustment very easy.

[motomike388]

thank you!!

[thump353]

also do a search for popping on decel at the top of the page, you will find more than enough info on this subject if your still having the problem

[thump353]

also do a search for "popping on decel" at the top of the page, you will find more than enough info on this subject if your still having the problem