Mikuni pilot jet size

[Mike Hufnagel]

With the 1 hour break in the rain today :)I was able to take my 250 up and down the street the street to work on the jetting. It was fully warmed up but would hesitate when whacked open. No hesitaion with the choke on.

I feel I'm having problems with the pilot jet. It doesn't really idle very well unless the screw is fully turned in.m Since it is a big pain in the ass to mess with the carb since there is very little room to work on it, I was wondering since it doesn't idle unless fully turned in, should I go up 2 pilot sizes or start with going up one pilot size? (It has a 35 right now.

Cheers


74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[Ed Chesnut]

IF it idles pretty well with the air screw turned all the way in with the 35 . . . then my guess would be go up to a 40.

(but I could be wrong . . . and you may end up with a 45)

Still, that's what I'd do.

Ed

Keep the rubber side down!

[Mike Hufnagel]

Thanks.   With the hassle of accessing the jets due to lack of space I wanted to skip a step to save some hassle.

Cheers

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[tomale]

I realize that it is a pain in the back side but skipping a step is not a good idea, you have not talked about the position of the needle. The needle jet and the pilot jet overlap in the metering of fuel and if the needle is too far down in the needle jet it could effect the size of the pilot jet. So before you go any farther, I would check the position, if the clip on the needle is in center groove and you still have to turn the air mixture screw all the way in to get it to run, then yes, going to a 45 is probably where you will end up, but you could end up with a 50 but I kind of doubt it.. The nice thing about finding the right pilot jet is that you need not ride the bike to get it right. Here is how you can tell if it is right, if it idles right and there is no hesitation when you blip the trottle and the airmixture screw is about 1-2 turns out... hope this helps. by the way, adjusting the airmixture screw is something that needs to happen depending on the weather.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74'250 hare scrambler (project)
74' 1/2 440 maico
78' 440 maico
72' cr125 Husky (project)
74' TM125 suzuki
93' RMx 250 suzuki