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carburetor problems

racerx51

CB750 Member
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troy ,IL
Ive been tring to get my 1976 cb750f carbs right and i want to know if anybody has any input on this.whats happening is my # 1 and #4 cylinder is running rich and my # 2 and 3 is running a bit lean. this is what i have done to remedy this with just partial success.First off ive dropped the float bowls to check if the previous owner fucked with the jets.I found the # 4 main jet lyeing in the bottom of the float bowl put it back in and started running on all 4 fancy that.All 105 s thats a factory jet setting.So i bumped them up to 115s all of them.put a brand new set of plugs to read and is better but not right yet.next i checked syncro its pulling very close to all carbs.i checked for intake leaks on 2-3 and negetive.have not checked needle setting yet. help if you can please!
 
To me it sounds like you have ignition issues now because 1 and 4 share a coil and one set of points and 2 and 3 share the other coil and the oil set of points. Weak spark will cause plugs to look rich because of incomplete burn.
 
that could be if i had points but i just installed a pamco ignition and got rid of the points. its the ultimate ignition so it has 75k coils awsome ignition by the way pete.im still wondering if ts needle position since the guy i bought it from was an over tinkerer.if it wasnt broke he would fuck with it anyway.but your absolutly correct about the points and thats why i got the pamco igniion thinking that might remedy the sutuation.
 
Check your float heights, if not set correctly they can give a rich or lean mixture. I don't have the details with me but they should be in the manual.
 
It would cause low compression which would affect the burn. I would think it would appear rich due to an incomplete burn. What are your compression numbers? Check that first before you do anything else.
 
It still seems strange to me that your problems are paired ignition cylinders 1&4 and 2&3. Let us know what you find out though.
 
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