Thread: Carb woes
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Old January 4th, 2022, 11:55 PM   #108
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

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MOTY - 2018, MOTM - Nov '17
Quote:
Originally Posted by marshallsmith27 View Post
@Danno XYZ by the time it was warm using the choke wanted to kill the engine. I definitely had to use the choke at first since the bike hadn't ran in a couple of months.
Idle is way too rich if choke kills it. Put factory 38 pilots in.

Quote:
Originally Posted by marshallsmith27 View Post
Doesn't the A/F adjustment screws only affect low RPM's?
Yes, set them according to manual. I think only later new-gen '08+ models have different L/R needles and different L/R mixture-screw settings

Quote:
Originally Posted by marshallsmith27 View Post
I went out there just now and tried it one more time since the battery isn’t dead anymore and now that it’s warm the it won’t idle at a normal rpm. it wants to shoot up to around 3500 and stay.
You're very close! Adjust idle-speed knob to set warmed-up idle to 1500rpms.

Then use choke for cold-starts. Choke will work as intended if idle-mixtures are stock. Won't be able to do it without stock pilots.

Remember, these bikes ran PERFECTLY when new leaving showroom floor. There's no reason to change anything. People only noticed going to bigger jets improved things only because they had dirty clogged carbs over time and were too lazy or clueless to properly clean them. So yeah, bigger jets and richer settings may compensate for dirty clogged carbs temporarily, but those deposits will continue to build and in couple months, they have to go to even larger jets again and again. But bike never actually runs as well as factory-fresh condtion. Now that your carbs may be factory-fresh clean, you'll want to use factory jet sizes and settings for everything.

BTW - right carb may have vacuum-leak. Inspect rubber-manifolds to head. Maybe swap them to see if fluctuations changes sides. Inspect slide diaphragm for leaks. Vacuum-ports/passages at front of venturis may be clogged.

Did you set valve-clearances identically for both cylinders?
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