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Motorcycle Repair/1980 cb650 carburetors

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Question
I have been having trouble with the carbs on this bike since the day I got it. I have removed and throughly cleaned all 4 carbs with special emphasis on the needle and seat 3 or 4 times and set the float level I believe the correct way. The problems are as followed. I cannot leave the fuel on unless the engine is running or the carbs will overflow every time. The engine takes an extremely long time to warm up to the point where it will idle steady, even when warmed up when initally taking off from a stop it sputters and stumbles unless revved way up around 5k. The bike does have 28k miles on it but I just installed new piston rings, grinded the valves and reset the clearances. I have also stripped the rust from the tank and installed a inline fuel filter. I just really wish I could get this bike to run strong and reliable like it should be. I know one of my problems could be a good carb synchronization is needed but theres got to be more. Thanks in advance.

Answer
I know I have found thr needle valve seats installed incorrectly in a couple
Honda CB Carburetors.
It does sound like they are not seating.
The Fuel levels could be set to high. The needle valves that you get in
the carb repair Kits today just dont match up appples for apples.
Does your Petcock have a vacuum line going to it?
Most Petcocks open with vacuum from the engine.
This is one way to try to insure these flooding issues dont happen.
Also some people put their petcock on the (PRI) position.
This (PRI) position is to be used only 30 to 45 seconds to Prime Dry Bowls.
This (PRI) position bypasses the diaphragm and can floor your carburetors.
I Rebuild carburetors for a Living.  www.viragocarb.com
I fix Yamaha's, Honda's about any Motorcycle Carburetors.
The Petcock could need rebuilding. Maybe its the problem.

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william joseph stack

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I specialize in Virago carburetors. Internal parts sizes, Needle and jet sizes for each and every year and model. Hitachi and Mikuni. I also can give tech support and Tech Support for carburetor problems and issues. Carburetor tuning and syncronization. Carbburetor rejetting and dynojet installations for engine modifications. I know every needle and jet size for every Virago made. I have done over50 Virago carb Salesand Rebuilds in 2012. I have over 50 sets ofVirago carbs in stockright now. I Build, Ride and Breath Virago. I have both the 1983 Midnight Virago's. The XV750MK and the XV920MK. 1 of my 1981 XV750H is is Premier Cycles, Billy Joel's Bike Museum.... I am an Honest and Fair man. I am also a Finicky Perfectionist withmy carb work. Ihave all the obsolete hardto find carb parts. I have new diaphragms, new floats, I have the float level setting down to an art. I have fabricated transparent bowls for both version 1 and version 2 carburetors.

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