Jets & Shims

[Pokeyjoe]

I'm thinking of bumping up the jet size on my Scrambler. I currently have TORs, K&N, and a Jenks venturi. The jets are 120s with one shim. My questions is the effect of shims on jet size. Would having two shims be the same as a 125 jet?

I think I'll stick in the extra shim to see how it runs. If its better, I was thinking I'd remove both shims and go to a 125 main.

Thoughts?

 

[CommandoRdster]

Pokey,that actually sounds like you should be in the ball park right now with jetting.What's causing you to think you might be lean?

To answer your question,no,extra shims are not the same as larger jetting. They have no effect on WOT,or small throttle openings.If you've got a lean midrange it could help though.

 

[Pokeyjoe]

I went from a Unifilter to a K&N. It doesn't seem as quick at WOT as it used to. Maybe I need a shim AND a 125...

 

[The_Dog33]

You only really need to shim if you have a mid range flat spot that doesn't warrant a larger jet. Having shims doesn't make your jet larger just changes the amount of gas at any given needle height. It sounds to me like you may need a larger jet, these bikes come lean to pass emissions. That being said at WOT a 120 is a 120 no matter how many shims you have.