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  #11  
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Thanks much for all the replies!!! To answer a few questions, the carb is an early 38mm with a choke cable and NO fast idle linkage. I installed a new rubber plug in the tower that came with the carb rebuild kit after installing the 90 slow speed jet.

Based on the replies it looks like I am close with the current stock jetting. I'll play the the idle mixture screw to confirm it is not set too rich. Maybe the CR needs a longer ride open it up. Thanks much guys !!
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Set the idle mix when the oil tank is hot.
If you set it when it is cold the bike will be rich when hot.
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Quote:
Originally Posted by 02vette View Post
Based on the replies it looks like I am close with the current stock jetting. I'll play the the idle mixture screw to confirm it is not set too rich.
Yes, adjust the mixture screw for best idle. There will be a small range of adjustment that will give "best idle" and you usually want the screw set on the rich edge of that range.

These are pretty simple carbs. You can get best idle with different mixture screw settings with different size pilot jets, within reason. Changes in pilot jet size will change/affect your off-idle transition and small throttle opening cruise.

Too often this gets overlooked.
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"CV's kill high rpm power"........You are doing something wrong!
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Quote:
Originally Posted by 02vette View Post
Thanks much for all the replies!!! To answer a few questions, the carb is an early 38mm with a choke cable and NO fast idle linkage. I installed a new rubber plug in the tower that came with the carb rebuild kit after installing the 90 slow speed jet.

Based on the replies it looks like I am close with the current stock jetting. I'll play the the idle mixture screw to confirm it is not set too rich. Maybe the CR needs a longer ride open it up. Thanks much guys !!

Your .90 slow jet might be a bit too big for a restrictive standard exhaust system. Very big compared with the .75 that my XLCH left the factory with in 1977. But it had the humongous two into one monster exhaust so who knows how that compares with the CR's two into two system.
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Just found this on the forum while doing a search........

These are the jets that worked for me on a stock 38mm Keihin P28D SB13....

Initially the main jet was a 160 and the bike ran a little lean I bumped it up to 170 but the bike bogged at WOT. I settled on 165 which gave a good colour during a plug chop and no longer bogged. The slow jet I went from 90 to 100 and it improved the idle. Pump is 80.

This is with a K&N filter a little larger than stock (sticks out about 1/2") with stock looking but less restrictive small mufflers. I'll stress again these jet sizes are what worked for me. With an Ultima ignition it idles rock steady and steps out pretty well for an old Ironhead. I get 54 mpg (Imperial) which is about 45 mpg US.
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I ran this carb on my xlh with drag pipes for a bit and settled on 88 slow jet (J&P402-231) / 170 main jet (J&P 4000205). Like others mentioned - make sure you have the rubber plug in there, otherwise it'll never run right!
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@Brendan. Rubber plug is in. Just ordered a 165 and 170 main jet thru J&P along with a 88 slow speed. Also purchased a less restrictive K&N air filter. Thanks for the insight everyone !!
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Quote:
Originally Posted by Tomcatt View Post
Yes, adjust the mixture screw for best idle. There will be a small range of adjustment that will give "best idle" and you usually want the screw set on the rich edge of that range.

These are pretty simple carbs. You can get best idle with different mixture screw settings with different size pilot jets, within reason. Changes in pilot jet size will change/affect your off-idle transition and small throttle opening cruise.

Too often this gets overlooked.
Tomcatt - this is the issue I am having. Engine stumbles or has a slight bog until I get more into the throttle. Idle is great. WOT is great. Plugs look great. Just stumbles a bit around 1500 - 2000 rpm when rolling on the throttle. I think I will try a 100 slow speed jet. Just got back from a 15 mile ride.
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Maybe I'm just used to the current EFI bikes like my 2019. Been many years since I last rode Ironhead ))
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