Giving up on V42A Carbs- Need Help with replacements

[RCOBill]

I'm done, after weeks of working on this bike, going through the Carbs and adjustments, I can't take it any longer and I'm done with the V42A carbs. Please help with inputs on replacement options, web sites and or any other information on what works and what to avoid would be very helpful. Well not completely done, is there anyone within the Los Angeles area willing to put their working carbs on my bike, just to test the bike out with known good carbs. My last hope is I could see something as a clue looking at a known good set of carbs and mine..  
(1981 CB 750 stock motor)  Timing checks, good spark, 175 PSI and all cyls are within 5 PSI of each other. New carbs boots, rebuild kit installed, checked the idle jet holes and they are not plugged and its adjusted per the book for a rebuilt carb bench starting point. It will start but not idle for long, stalls right away, will rev but stalls, it will run and sounds like it's on all clys with short bursts of starting fluid and it will keep running until spray is stopped and it stalls. I have a second set of 1970 something carbs off eBay, said to be rebuilt and they look it inside and out, but will not fit the bike, what is up with that, I would think a 750 CB 1970 something would be the same size as 1981 ???  Bike ran last fine last summer, sat winter with fuel valve left open, carbs were bad but after cleaning 3 times and blowing down with 100 psi they are clean..  Are the VB42 A not a carb that can be rebuilt or what ??

[sgtslag]

Welcome to the Forum.  Can't shed too much light on the issue, but I can say that the 1981 carbs are Constant Velocity, and the pre-1979 carbs are not -- very different animals (1979 was the first year of the CV carbs).  Are the VB42 A carbs OEM?  The OEM CV carbs can be rebuilt, they are definitely not throw-away's.

Do you have a stock airbox, or are you using pod air filters?  The CV carbs are extremely difficult to configure with pod air filters -- they only work properly with the OEM airbox...

Shoot us some additional information on your set-up, and the 'CB750 Hive Mind' will attempt to help you.    Cheers!

[TOOLS1]

Honda changed the engine from a SOHC to a DOHC in 79, and went to the CV carbs. I personally do not care, for them, but like Sarg said "they are not throw aways." From what you are describing, you are having a fuel delivery problem. I do not know to what extent, you went to to clean the carbs, but with out a total dis-assembly it is all but impossible to get them clean. There are several threads on here about rebuilding these carbs. Just use the search feature. However if you really want new carbs go to sudco.com They have replacement carb setups for these bikes, but they are pricey.
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