running lean with 170 main jet

[Blysster]

OK, I have yet another problem. I am running a 170 main jet/42 pilot and it is running a little bit lean.

Should I try going to a bigger main jet or could the problem be something else? 170 seams really big already.

I live at 500 feet or less than sea level and my valves are set exactly at .005 for exhaust. Intake are at .004 inches of clearance.

Any help is appreciated.

[Kadafiy]

Correct me if I'm wrong but don't the dynojets run a little larger then the stock jets. I'm running a 160 main now and it runs great. Just go larger on the main and take a plug test.

[BornOnFire]

You may want to mess with your fuel screw. Turning it out will richen the mixture. You do not want to be out more than three turns though. If you have to go beyond that, go up one size on your jet. Also, you may want to move the clip on your needle jet down one notch to richen the carb from 1/4 throttle to the 3/4 range. Whatever you do, do a little at a time and check the results. Small adjustments can make a big difference. Good luck.

just go up on the main till it sputters at full throttle, then go down one size and it will be jetted fine.

[Blysster]

Thanks all..

Few more questions. Where can I buy 175, 180, and 185 main jets (dynojets)?

and what kind of jets are the stock ones?

i assume any shop in your area would have jets. stock jets are made by keihin. Does your bike lack a bit of power in mid range? cause if so you could try raising your needle 1 clip

that sounds kind of rich though? i have a 160 and my bike runs good, sure you're not running rich?

[Blysster]

Nope, the bike runs perfect.. it has great power throughout all of the throttle.

When I do the park plug test it is white.

[400exJOE]

If it is perfect running than it is not lean. Gas has presevatives added to it which make plug reading inaccurate. To me a 170 with just a pipe seems lean to me. Go by how it runs, not the plug color.:)

[deansfastway]

Yeah, plugs are really hard to read unless you have experience. A way to fool the motor into being richer is to tape off part of the airbox or pull the choke on halfway . If it runs better l;ike that you might want to rejet , but 170 sounds pretty rich to me. We have quite a few EXs running out here in Jersey (@sea level) on 42 pilot and @ 158 mains ,with radical motorwork, maybe your carb is loose or the intake is coming delaminated(rubber/metal) If the spark plug is loose the bike will run lean also .

[Leo]

isn't there a big difference between a keihin 170 and a dynojet 170?

I think some folks are reffering to the keihin sizes, and some are reffering to the dynojet sizes..

Makes things a big confusing :D

Leo