Tuning help

mase911j

mase911j

Location
virginia beach
I've seen several tuning recommendations for the keihin CDK II blue race carbs, but none of the motors were like mine. Im also going to rebuild it since i dont know what pop off spring is in there (or the size of the jets for that matter). So any suggestions on that would be great too.

Any help would be great, thanks in advance!

- Higher comp head (mariner), standard pistons
- lightened flywheel
-dual cooling (doesnt matter for this i dont think)
-west coast manifold and head
-supertrapp exhaust
-stock 5-wire electronics
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kevbo

kevbo

Location
dfw
A 15.5 will likely be a little on the high side for a 650 with a Westcoast pipe. You can make them run a lot smoother and reduce load by bending the leading edges down and trailing edges up .1 inches or so. You can reduce wear on the splines by cleaning, greasing, and adding some sealant in front of the O-ring after the dirveshaft is installed. Solas impellers need only a good stock seal.
 
mase911j

mase911j

Location
virginia beach
kevbo said:
A 15.5 will likely be a little on the high side for a 650 with a Westcoast pipe. You can make them run a lot smoother and reduce load by bending the leading edges down and trailing edges up .1 inches or so. You can reduce wear on the splines by cleaning, greasing, and adding some sealant in front of the O-ring after the dirveshaft is installed. Solas impellers need only a good stock seal.
Click to expand...
Do you have any suggestions for the jets and pop off spring?

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kevbo

kevbo

Location
dfw
Pilot jets are sensitive, an 82-85 will usually work depending on popoff. Main jets should be in the 150-160 range. Just power tune the top screw and see how where it ends up at peak power. Change the jet until its around one turn out. I have never found the Pop-off pressure to be very critical on single Keihins other than affecting the bottom screw and pilot jet. And remember, the bottom screw is for adjusting low idle mixture only.
 
Last edited:
mase911j

mase911j

Location
virginia beach
kevbo said:
Pilot jets are sensitive, an 82-85 will usually work depending on popoff. Main jets should be in the 150-160 range. Just power tune the top screw and see how where it ends up at peak power. Change the jet until its around one turn out. I have never found the Pop-off pressure to be very critical on single Keihins other than affecting the bottom screw and pilot jet. And remember, the bottom screw is for adjusting low idle mixture only.
Click to expand...
Awesome. Thanks!

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mase911j

mase911j

Location
virginia beach
kevbo said:
Pilot jets are sensitive, an 82-85 will usually work depending on popoff. Main jets should be in the 150-160 range. Just power tune the top screw and see how where it ends up at peak power. Change the jet until its around one turn out. I have never found the Pop-off pressure to be very critical on single Keihins other than affecting the bottom screw and pilot jet. And remember, the bottom screw is for adjusting low idle mixture only.
Click to expand...
I just got around to messing with it. I havent messed with the high screw yet, but i cant get it to idle (at any point from 1 1/8 to 4 turns out on the low screw), it dies as soon as i let off the throttle after dumping fuel down the carb. The carb was rebuilt a few years ago and it sat empty (no fuel), so not sure if i need to do it again. I did pressurize the tank to see if that would help, and it didnt. Any thoughts?

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