Problem low rpm jetting on a fcr 41mm remade to 44mm.

CUL8ER · May 17, 2006

Hey..
Have a question if anyone could answer it... we have made a 44mm carb out of a 41mm keihin carb with no tps on. But i have trouble to get it to run properly on low rpms. The big problem is that when i have put in the proper slow jet and turned in the fuel screw properly it idels great.. have rev meeter so i see the revs go down perfectly and stops there... but when you riding the bike, when you coaming in full speed into a corner and drop throttle of and start breaking its popping and banging like its way to lean.. so i had to put bigger slow jet in but then its to rich at idle and are hard to start... but dosent popping and banging when running...
Could this be a problem du to carb is 44 and you mabe need to change the slow air jet? If so is it a bigger or smaller slow air jet i need to test?

// Thx in Advance

husabutt · May 17, 2006

CUL8ER said:
Hey..
Have a question if anyone could answer it... we have made a 44mm carb out of a 41mm keihin carb with no tps on. But i have trouble to get it to run properly on low rpms. The big problem is that when i have put in the proper slow jet and turned in the fuel screw properly it idels great.. have rev meeter so i see the revs go down perfectly and stops there... but when you riding the bike, when you coaming in full speed into a corner and drop throttle of and start breaking its popping and banging like its way to lean.. so i had to put bigger slow jet in but then its to rich at idle and are hard to start... but dosent popping and banging when running...
Could this be a problem du to carb is 44 and you mabe need to change the slow air jet? If so is it a bigger or smaller slow air jet i need to test?

// Thx in Advance

I am nowhere near a carb guru, but........

I would be inclined to try using a slow jet that allows for proper starting but going as large as possible and also using the next richer slide. Since you have opened up the carb so much all of your settings will probably need to be richened to make up for loss of venturi signal.

Taffy · May 20, 2006

cul8er

when the carb was bored did you make sure that you machined all 3mm off the top and 1.5 from each side? did you leave the bottom of the carb alone?

secondly, don't go by the popping and banging. you should have set the PS to the best snap wheelie position and THEN and only THEN do you worry.

if all was as you say, which i doubt (sorry but what do you wanna hear?) you need a leaner needle straight for re-starting when warm and idle. whatever your third suffix letter is - increase it so EKP needs to be EKR or EKS. if you gimme your code i'll check one out for you and the clip pocition.

regards

Taffy

Problem low rpm jetting on a fcr 41mm remade to 44mm.

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