Topic: CB750 Engine/Carb Compatability

[Accolay]

Getting back in the saddle again. Want to start finishing the backlog of projects.

I have a 1977 CB750 rolling frame with title, missing the engine/carbs/airbox and I think I have a K4 engine from the serial number: 2356323

Just wondering if the engine will fit and if so what carbs will I need? Haven't really decided if I should either sell it and spend time with something else or start buying parts.

Thanks.

[Old Scrambler]

Motor will slide right in......but you will need the off-set sprocket (Cycle-X) to match your chassis........standard 28mm carbs...........you may have to play with the fuel-rail depending on which side of the tank fed the carbs.  Standard air-box........but try to get a 77-78 for the best air-intake. 

[seanbarney41]

I have a 78k motor in a 75 frame.  Old Scrambler has it right on the Cyclex offset sprocket.  You can also mix and match the 77/78k sprocket carrier into the earlier wheel with the correct mix of spacers.  Chain to rear shock clearance is very tight, so any shock that is bigger in diameter than the stockers in the path of th chain is going to require further mods to work.   As far as carbs, any will work but you have to have the correct carb and airbox boots...77/78k pd carbs require different boots than the '76 and earlier roundtop carbs.

[Sdsbassist]

So if I have a 75k engine in a 77K, I will need this sprocket as well?

[Sdsbassist]

I have a sprcket from a 78 motor...would that bolt on if I do need an adjustment?

[seanbarney41]

So if I have a 75k engine in a 77K, I will need this sprocket as well?

you will need to use the sprocket carrier(or entire wheel)from a '71-'76 k model and maybe custom wheel spacers?  The Cycle X sprocket page has pictures and explains this pretty well...
http://www.cyclexchange.net/Chain%20Sprocket%20Page.htm       down at the bottom of the page
also search here, there are several old threads on this