Topic: CB650 carbs question

[Raymond_Y]

Hi, I have a 1980 CB650 engine that I intend to use for a future care racer project and have a question on the carbs.  I have a couple of sets of carbs (069A and PD46) which I hope I can use for the project.  My question is around the carb size.  All the specs I have found suggest a 1980 CB650 had PD51 carbs that were 26mm.  However, if you measure the internal diameter of the inlet stubs they are 30mm, which seems strange.  Could I use the PD46A’s or should I consider perhaps taking the opportunity to fit bigger carbs?

Raymond

[TwoTired]

The venturi throat size is what is important.  That is smaller than the inlet or outlet.

While the 069a and pd46 carbs have 24mm venturi's, yes they could work.  But, you will unlikely get the top end performance that you would with 26MM venturis.

Probably not too important for a fashionable show piece, though.

Cheers,

[DaveBarbier]

PD46 carbs won’t fit because of the head inlet spacing. Early 750 carbs do, unsure which models. This only works for 79-80 650’s.

[Raymond_Y]

I have a mount plate that is the correct spacing, so can be creative in mounting carbs with the correct venturi.  Can any one advise which early 750 carbs may work.  PD42’s seem the most common.

Raymond