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Crazy jetting problem!!!

1013 Views 6 Replies 5 Participants Last post by  sumo bill
This is driving me crazy!!!!!!!!!!!!!

As some of you know, I installed a 30mm Kehin PD Carb on my CRF230 replacing the stock 26mm PD

It has a 40 pilot, 1.75 turns out on the fuel screw, 37D slide, 85A needle, and a 158 main.

Engine has a 11:1 piston, BBR Cam, BBR Pipe and some mild head porting.

When running the bike at WOT, and then rolling off the throttle (not chopping the throttle) the engine momentarily cuts out, and then recovers.

Not a huge issue when in the dirt, but when mid corner racing SM, it could really ruin my day....can you say highside!!!!!!!!!!!!!!!!
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Also consider the following:

A carby needs a certain "air speed" to create enough suction at the venturi for a good mixture.
If a smaller engine, like your 230, is fitted with a carb too big for the application it may very well be that at lower rpm the negative pressure, due to lack of wind speed, is not high enough to create a good enough mixture.

Just a thought ... haven't had a chance to find out what the biggest size carby for a certain application may be.
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