I just got my 686 back and, installed.. I'm still running the breakin tanks but, it is running STRANGE!

My builder thought it should be all set w/ jetting but it has to be wrong. Off idle it sputters. If i "slow roll" as in turning around for another lap and, slowly get onto the gas - it sputters and, hesitates (as if it was hitting a rev limiter but, no it is not) then slowly cleans out and, begins to accellerate normally. It also does this after a quick whack of the throtte = for instance, I do a small wheelie drop the front end and, get back on the throttle, it cuts out and, starts the sputtering and, sometimes dies.

Please, if any of you Raptor guru's can lend a hand it would be much appreciated. I believe i have 175/172 jets and, the clips on the 4th position. I will be calling my builder tomorrow but, i'd like a few opinions.

Also, my plug is kinda dark as in rich but, before the work when it was just piped and, jetted it was the same color but, ran perfect.

My builder is in AZ and, said he had the jetting spot on for my alt since his was the same (500ft-900ft). But, i think our high humidity may be a factor?? Thanks a bunch guys, i'm pretty green w/ tuning and, now i'm petrified to ride it.

 

float level?

 

That would be the first thing I would check. And depending on your cam, piston, and porting that sounds a little lean on the mains to me, but all of them are different.

 

Can some one explain exactly what float level is and, how to fix it or test if it is wrong?

I'm lost when it comes to tuning carbs.

 

Floats are what allows your bowls to fill up with fuel,,,,for the carberator to use.

If they overfill,,,,the excess fuel creates a very rich condition at low Rpm's (especially on uphill grades)(lot of lost power, torque).
If they underfill,,,you might run out of fuel at wide open throttle.

Search (sixsixt, float) in the yamaha forum.

(it is hard to tune your carbs if your floats are off) Use a clear tube to check your fuel level in your bowls.

 

I doubt it is the floats then. When it was on the Dyno in AZ it made Huge HP and, there were no drop offs in the power range. It must be something in the jetting from Mesa, AZ to here in Chicago, IL. They had my carbs with it and, asummedly made all the adjustments.

Something in the carbs that controls the low speed i'm thinking?

I've also been told to check that my choke plunger was seated properly when I put it back together. Can't wait to get home.

 

Too dark too rich. Try 165-170 & then see how it runs......

 

does your reverse light come on??

 

Float levels can be checked with a clear tube with one end connected to the carb drain nozzle(on bottom of carb), the other end of the tube then bent 180 degrees up against the carb. The level of gas should rise to the carb mating surface(where top & bottom end meet) in the center of the carb(left to right).

Other way(harder) is to remove carb bottom & with float leaning at approx 30 degrees away from you the float tang should just rest up against the needle valve but not be depressing it when the float is approx 1/2 " above the mating surface. Or jsut make sure the float is parallel with the mating surface under same conditions. Yes, this way is very hard to explain in writing & is best left to having someone who knows show you how or just keep trying yourself until you understand it.