yz125 KIEHIN jetting

[confusedtech]

I took the mikuni off my sons 2002 yz125 and put on a 59mm Kiehin. The main jet in it was a 170. The bike runs good low and mid but sputters on top end. I have gone up on the main to a 205(5 at a time) and it hasn't fixed it yet. Should I go down? Is it a rich sputter? It doesnt foul the plugs. I had Eric do a 144 bore for me but it just doesnt seem to have the top I think it should. Just wondering if anyone else runs a Kiehin on a 125.
thanks confusedtech

 

[Eric Gorr]

Sputtering could be too rich but it depends what needle you have. You had the problem of the wrong crankshaft in your bike, did you ever fix that?

 

[confusedtech]

Yes I have. Eric you have a good memory for thinking about that. I run 32-1 110 race fuel with amsoil dominator oil.BR9 NGK race plugs. I've advanced and retarded timing with no help. I have not changed the needle and really have not looked very closely at it. I put the 170 main back in and am going to try a more oil to fuel ratio to see about leaning it a little once it warms up some,currently 20 degrees around here.

 

[confusedtech]

Ok Eric I took the slide out of the carb to get the numbers the slide has a star symbol and a 6 or a 9 ( *6 or 9*) more like an hourglass shape than a star. the needle has R1469N with an -S under those numbers.
thanks confusedtech

 

[hot125mod]

is your bike a 98 or 99 by any chance

 

[hot125mod]

and i hope you ment 39mm instead of 59mm carb