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Old November 14th, 2017, 12:05 PM   #8
jkv45
Rev Limiter
 
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Name: Jay
Location: WI
Join Date: Jul 2013

Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes

Posts: A lot.
MOTM - Jun '18, Oct '16
Can you post a photo of how your vacuum hose is attached to the carbs?

As others have mentioned, if it runs fine on "Prime" but not on "On" it suggests an issue with a lack of vacuum or a malfunctioning petcock.

The photo you posted is for a PreGen carb, and yours is a NewGen - so they won't be exactly the same.

You can test that you have vacuum by removing the hose from the petcock and plugging it temporarily. Set the petcock to "Prime". Then start the engine and let it idle. Remove the plug on the vacuum hose and quickly put you finger over it - you should feel a vacuum. If you remove your finger you should hear the engine RPMs change (and air rushing into the hose) and the engine may stall (not a problem).

If you get vacuum there it would suggest the petcock is the problem.
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