77’ Cb750F Carb Compatible with 78’ CB750K8

[77CBilly750F]

Bought a refurbished carbs on eBay for my 77 CB750F. After discovering a vent port next to the fuel inlet on the carb and some research I found out it is a carb off a 78’ CB750K8.

Are these carbs compatible and tuned the same? They look almost identical. And where should I route that vent line? It seems on the K8 it was routed back to the airbox. I am wondering if I can just route it down next to the bowl overflows.

 

[dirtdigger]

Are the carbs the same side on the engine side where it goes to the head? Will it fit the carb boots? Yes they are basically the same and they will tune the same but beings someone else rebuilt them you have no idea what jet sizes they put in or what float level they set them at. Also you dont know if they use oem jets or chinese aftermarket jets which have been know to not be correctly made causing running and tuning issues. Yes you can run the vent pretty much where ever you want if your not running the airbox

 

[77CBilly750F]

Are the carbs the same side on the engine side where it goes to the head? Will it fit the carb boots? Yes they are basically the same and they will tune the same but beings someone else rebuilt them you have no idea what jet sizes they put in or what float level they set them at. Also you dont know if they use oem jets or chinese aftermarket jets which have been know to not be correctly made causing running and tuning issues. Yes you can run the vent pretty much where ever you want if your not running the airbox

They said the main jets are 115s which is different than stock I think. 105s? Will have to ask what the jet size is. They fit into the engine side and air side boots.

Thanks for the reply!

 

[madmtnmotors]

I have both K and F models of 78 vintage and move carbs freely between the two. Jet to suit.

 

[77CBilly750F]

I have both K and F models of 78 vintage and move carbs freely between the two. Jet to suit.

That’s a relief. The new carbs were expensive. I will just need to work on setting them correctly.

 

[hinksy]

Some slight differences

 

[77CBilly750F]

Some slight differences

This helps a lot thank you. Will see how she runs and tweak towards the f model jets