250R Jetting Question

[Live2Ride300]

Ok, I have the snorkel on, air box lid on, a uni air filter, Paul Turner mid range pipe, lrd silencer. Right now im running a 170 main jet, a 42 pilot, and i have the air screw set at stock, needle is 3rd clip from the bottom. It is running a little rich, it just fouled a plug, it had alot of oil on it. Im not sure where to set the air screw at, but will backing out the air screw lean it up enough so that its running right? Or should I drop to a 168 main? I live in New Hampshire, and its like 30-40 degrees. Thanx so much for help!

[Geoff Thomas]

Well you can back the air screw out but that probably won't fix it. That only adjusts the idle to just off idle circuit. You want it set at the point that the engine revs the highest. If you have to screw it WAY out like 4 turns or so they you need to change the jet. Also if you dno't get any change until just before it seats you need to change the jet. The best way to see if the main jet it right is to put a NEW plug in it and take it out and ride it down a straight holding it in about 4th gear WOT for a good 5-10 seconds and then hit the kill switch and pull in the clutch. Come to a stop and pull the plug being very carefull because it will be HOT! You might want to let it cool a bit first. Look at the plug and at the very base of the porciline down deep in the plug it should be a medium brownish color. If it is really dark then you need to drop it one size if it is white then you need to raise it one size. You should be able to feel the difference in how it runs when changeing the jetting and where it runs the best is where you want it. If you get it to lean it will start to detonate and you will melt the piston so be careful on how you run it. If it feels a little sluggish through the mid range you may need to lower the needle. If you lower it a little and it seems to clean up try lowering it one more until it seems to get worse or stay the same then go back one setting. Once you get in tune with your bike and get to know how it runs when it is really running good then you will be able to pick up on weather it is running lean or rich and will be able to fine tune it better. Also I would recomend mixing your fuel to 32:1. Personally I like HP2. It seems to burn nice and clean and doesn't leave a lot of residue or carbo build up.