Topic: Carb jet sizes for CB400F Yoshimura Kit

[Steve Reeves]

Hi all,
i'm after some advice regards what size main jets i need for a yoshi 466 400/4.
Bike currently runs stock pipe, K+N individual filters.
The motor is taken to 466.  It has a really bad flat spot starting at about 4500rpm.
At present standard mains are fitted (75 i think).

[turboguzzi]

I wouldnt run a 466 400 on the tiny stock carbs in the first place, but that's me....

[Triffecpa]

I run 85 main jets in my 400F track bikes.  I run open velocity stacks and basically open exhaust, but I'm also at 5000' elevation.  I can also get away with occasionally using 90's, but 95's are definately too rich.

I don't know that more displacement necessarily means bigger jets though. 

Repalcement jets for the 400's aren't easy to find.  There is a seller on Ebay that sells a set of 16 jets but they are near $50 plus shipping.

Sudco has some of the correct Keihin jets, but they have some funky sizes.

I've had good luck with buying .80mm and .85mm drills and drilling out the stock 75 jets.

Nothing unique about jetting a 400F compared to any other application.  Put in a new set of plugs, run it at high RPM first and do a plug chop and see how they look.  Make sure that your carbs are clean and that the floats are set to teh correct height first.

Tracy

[Steve Reeves]

Cheers Tracy,

I will do abit more research.  Thanks for the help.

Steve R