34mm Mikuni flat slide carb adjustment

[Saxon_20]

New guy here.. I bought a stock 1998 Banshee and proceeded to do BF4 reeds, Toomey T5’s, 34mm flat slide Mikuni’s, Pro Design Coolhead and a +6 swing arm. I’m in Salt Lake City, UT with an elevation of roughly 4300ft. Does anyone have a recommendation for jet sizes?? I currently have a 270 main which seems kind of small. Bike starts right up, idles great, but once I hit the throttle in first it will kinda spudder before the power band. Any information would be appreciated!!

Edited March 16, 2018 by Saxon_20
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[Ducman]

I used to have 34mm FS Mikunis.  (still have them in a box)  The main jet size and pilot size are pretty similar to what a stock banshee carb would take.  The main jets are interchangeable with the stock carb jets, the pilots are not.  Do you still have the airbox?  Lid on or off?  Type of filter?  270 is probably not far off where you need to be depending on the air box restrictions, but maybe a little lean.

 

The needle jet is a little trickey.  You can raise or lower the needle same as stock for leaner or richer, but rather than changing the needle altogether for a leaner needle you change the dump tube that surrounds the needle.  When I got my 34mm mikunis out of the box they came with way too rich of a dump tube so I had to get a much leaner one.  That may be your problem.  When you ride at WOT, if it cleans up and gets on the pipe and revs out, then its probably just the needle giving you the problem.  You probably need a leaner dump tubes.

[Ducman]

Funny thing, when I recently got my banshee built at Redline, Cam and I discussed keeping the 34mm Mikunis.  Cam was more familiar with the kehins and said he could probably get them tuned better and If I made changes he could give me better recommendations If I had kehins, so I went with the Kehin 35pwk.  He said that most builders use Kehins except for the builders in the UT area and they tend to use Mikunis for some odd reason.  Maybe you should ask a builder in UT what dump tubes to run.  I could tell you which ones I ran if I go home and take one of my old carbs appart, but I'm at sea level, and you are at 4300, so you might need an even leaner dump tube than I did.