30MM KeiHein Carb Tuning

Newt232 · 09-08-2019, 09:34 PM

Hi all,

I upgraded the carb on my Tomoto/Hawk/Whatever to a 28 or 30MM carb. This was about a year ago. I had some consternation with the throttle cable no longer being long enough, and then the longer replacement having too little travel. I got it all sorted out, and have the bike tuned to where I can reliably kick-start it and jettisoned the battery. Since swapping the carb to a larger diameter and attempting to increase the jet size to the maximum that came with the bike, I can not get the thing to put out nearly as much power as I had with the stock carb. I can get up to about 6-7K RPM and then the throttle isn't wide open, maybe 1/2 or 3/4, but if I give it more gas it just makes the engine rpms unsteady, and the exhaust note becomes more cacophonous. If I hold the throttle wide open, I feel jerks as if the motor wants to take off, and then drops back down in rpm's. It's very odd, and I'm not sure if I can get a fix for this but it's bugging me as my top end has really taken a hit due to the change and I was hoping for the exact opposite effect.

What do I do to fix this? I've already swapped around the jets and I think I've moved the circlip on the needle around too... I don't like feeling like I'm going slower than traffic and building up a line of drivers behind me, so I've not been riding much since the changeover.

09-08-2019, 09:34 PM	#1
Newt232 Join Date: Oct 2018 Posts: 25	30MM KeiHein Carb Tuning Hi all, I upgraded the carb on my Tomoto/Hawk/Whatever to a 28 or 30MM carb. This was about a year ago. I had some consternation with the throttle cable no longer being long enough, and then the longer replacement having too little travel. I got it all sorted out, and have the bike tuned to where I can reliably kick-start it and jettisoned the battery. Since swapping the carb to a larger diameter and attempting to increase the jet size to the maximum that came with the bike, I can not get the thing to put out nearly as much power as I had with the stock carb. I can get up to about 6-7K RPM and then the throttle isn't wide open, maybe 1/2 or 3/4, but if I give it more gas it just makes the engine rpms unsteady, and the exhaust note becomes more cacophonous. If I hold the throttle wide open, I feel jerks as if the motor wants to take off, and then drops back down in rpm's. It's very odd, and I'm not sure if I can get a fix for this but it's bugging me as my top end has really taken a hit due to the change and I was hoping for the exact opposite effect. What do I do to fix this? I've already swapped around the jets and I think I've moved the circlip on the needle around too... I don't like feeling like I'm going slower than traffic and building up a line of drivers behind me, so I've not been riding much since the changeover.
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