Topic: VB54 Carb indetification for CB650

[TomasK]

Hello there! Having a bit issue ,need help to indetify CB650 carbs ,it is written VB54 C A T F and japanese sign. Letter A written in square.My jets was without any marks and now i dont know which to use.My bike came from Germany with 4 in 1 mopad exhaust.I know here is some one who can help me!

[fizzlebottom]

The scant few things I've found about VB54 carbs is that they were for the EU market. That matches up with the fact that the bike came from Germany, meaning that it probably also has the milder camshaft.

Now about the jets. If I am reading correctly, you have an '82 CB650 (non-Custom) with VB54C carbs built for the French market. That would mean you use #98 main jets and the pilot screw 1 3/4 turns out.

I think that seems right to me.

[TomasK]

My bike by the docs is 1981 single cam,is 4 in 1 exhaust makes any difference ? Its definetly not a OEM. Will try out 98

[fizzlebottom]

My bike by the docs is 1981 single cam,is 4 in 1 exhaust makes any difference ? Its definetly not a OEM. Will try out 98

Sorry, I think I meant to say '81 not '82. My thoughts on the jetting still apply, even with that exhaust. The CV carbs of this era don't really care much about exhaust. Yours originally came with a 4-into-2 setup, and my '82 CB650 Nighthawk came with a 4--into-4 setup. We both now have 4-into-1, and I can tell you I have not had to change any jetting at all. I may have fiddled with the pilot screw a smidge, but that's it. You shouldn't have to jet differently either.

My hope for you is that the bodies of those carbs are 100% identical to the VB44 carbs that came with North America spec bikes. That way you could get a rebuild kit when needed and have all of the right o-rings. You'd just have to pay attention to the different jets. For example, the carbs on US bikes came with #120 mains and #35 slow jets. Your #98 mains are quite different and the pic you posted doesn't even mention slow jets. Any more info on that in your manual? How about any mention of main air jets?

[TomasK]

Good to hear about exhaust! There is built in slow air jet and main air jets and in the bottom needle jet holder with main jet.Somethere i have 98 and will try in near future.

[fizzlebottom]

Cool. Everything in those pics looks exactly the same as the VB44 carbs. You have non-removable air jets and a #98 main instead of a #120. I still don't know what your slow fuel jet is though, so that's a curiosity. If you do end up replacing any jets aside from the pilot screw, don't use aftermarket junk. Use genuine Keihin stuff, otherwise you might end up chasing gremlins.