Topic: Cb650 carb Question

[fdbrat]

Ok Ive read I can install the cb750 carbs (1973 - 1976) on my 1980 cb650. Before I give up on my 650 carbs Id like to ask a few questions if you all dont mind. Oh and the reason is open pipes and uni pods.

1: I have slide carbs. Is it possible and if so, How do I get to the needle jet, so that I can move it a notch or so? Or do I have to shim it? Or is this not even possible?

2: I keep getting mixed meassages about the AFR screw. which way is leaner and which way is richer?
I believe I read somewhere cb650 carbs might do things backwards.

Thank you HONDA

[cb650]

No adjustment on the needle.   No the 650's arent backwards. Out is ritcher.

[MJL]

Depends on the carbs. The '81 650 has the non adjustable needles, I bought a jet kit that had adjustable needles in it.  I think the 79-80 650s have different carbs with adjustable needles.

To get to the needles you'll have to take the top of the carbs off and pull the slides out.

[cb650]

yes the 79/80 had diff carbs but the neddles arent adjustable.  Not like the older carbs that you can change what slot they use.   Just took the top off one.  just a adjustment for sync.

[joe1028]

if they are the type with the cover with two screws on top they will have adjustable needles you need to put the clip near the bottom with pods (#4 to start with) and go up about 6-8 sizes on the m/j(for a starter). if the low speed or pilot adjustment screw is on the side and near airbox it will be out lean in rich (air adjustment).if on the engine side (bottom) it is a mixture screw and out rich in lean...this is the case for most all idle(mixture or airscrews) adjust screws on all carbs too.........joe

[cb650]

Joe have you actually done this to a set of 650 carbs?  I looked again and dont look possible.  Remember in 79 they started to make everything  non adjustable.  They even had limiters on the mixture screw. 

[cb650PK]

79 have adjustable mixture screws and 80 have limiters on them. You have to use shims under the needles on these carbs . I wonder what is the benefit of using 750 carbs on stock engine besides not having to deal with the pump and air cut-of valves.

[scunny]

just to confuse the issue, my 79 carbs dont have the air cut off valves

[joe1028]

if you looked at it then you should know the answer, it either has clip grooves or it doesn't....remove a few screws to find out for sure.....should be adjustable if not use shims...just make sure that once shimmed at full open throttle the needles can not come out of the needle jets.

[cb650]

You musta done it somehow so I stand corrected.