Jetting FAQs

Elko - I will put an advanced section!  Thanks for the suggestion!

92, Elko already said it as well as anyone (regarding the pilot), so I won't need to repeat it

Spiderdad - hope it comes in handy someday!  
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Sarted an Advanced addition on Needles - just for you, Elko

God willing Chud doesn't read this - he get's all hot and bothered about needles, and I fear all this information would make his head explode  
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STICKYYYYYYYYYYYYYYYYYYYYYYY

Where did you learn all this from Skip?  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

23 years of working with bikes, 92  
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Yeah, I suppose so! lol

23 years.. you were how old when you started?  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

14 yrs old when I got my first bike.  14yrs old and a month when I tore down the motor and rebuilt it.  14yrs and 3 months when I rode it over to the SOB's house who sold it to me and gave him a good whooping for selling me a 'perfect' bike with a bad crankshaft.  
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I know the feeling. I was sold a 'perfect' bike, it was his 'pride and joy'! Shame he didn't know a thing about motocross bikes, running it at 25:1 and never cleaning the air filter! Oh well, we learn the hard way!  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

What was your first bike?  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

1984 Kawasaki KX125  
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Skip, I want to make my bike start easier at the ice races when its super cold out.

i guess when its 0 or less. I think in mass we r at 480 ft.

my bike runs great when warm and has perfect throttle response coming out of the corners it lofts the wheel with little effort on the ice.

i've tried to just up the pilot size from stock but it doesn't really start much easier and kinda loses that snap.
also i've done 1/4 turn increments in and out with the air screw,
any suggestions??


MODEL   MAIN   PILOT   NEEDLE   POS SCREW


YZ250   170   48   N4DG   3RD   1 1/2  

ML, is that a '97 YZ250?

I'm surprised it's running that good for you in the cold!  That jetting should be WAY lean!

You can try to richen your pilot circuit to help the starting, and then go with a lightly leaner slide cutaway to get the resulting soft throttle to be snappier..

I'm stills scratching my head as to how you're getting away with running stock jetting at sub-freezing temps.. it goes against everything I know about carbs, and the YZ250 in particular!  
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ok then i'll add this wrench.

I purposely run a UNI dual stage filter and oil the inner section extra heavily to compensate for the add air density. but only in the winter when racing. During the sumer months I run a 168 main and sometimes even a 45 pilot and keep the inner stage completely dry and only oil the outer section.

my only tru complaint with the 97 in the summer months is a slight mid throttle stumble on long steady sections like riding down fire roads or beside the railroad tracks.

i can easily roll the throttle on slightly and the condition disappears.  

If you roll the throttle on and the condition disappers, then I'd suggest you lower your needle (raise your clip) a notch and see what happens. Heck, I have 1/2 clip shims (you can get them for a few dollars a bagful at Sudco), if 1 clip position is too much of a change.

BTW - the N3EJ is a better needle for that motor  
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Skipper:
If you roll the throttle on and the condition disappers, then I'd suggest you lower your needle (raise your clip) a notch and see what happens. Heck, I have 1/2 clip shims (you can get them for a few dollars a bagful at Sudco), if 1 clip position is too much of a change.

BTW - the N3EJ is a better needle for that motor

AAH Ha!! That was my next question!! what was ur needle recommendation??


But u beat me too it.  

ok, i'll order that today.

do u know is it a different length or dia or both??  

i also have already tried moving the clip 1 step in both directions. but i feel as though it just moves the stumble to different throttle positons and never actuall clears it up.

with the differt needle would u keep the stock clip position??