Simple (i hope) carb question

[vegastruckee]

Hey everyone, OK so im getting ever closer to completing my 1978 CB750F cafe project but am stuck with my carbs right now. I have the bike running but need to finish tuning the bike. I dont have a manometer and was wondering if you may have a GENERAL setting that would put my adjustments CLOSE for now until I can find a monometer to properly adjust my carbs. Also on top of carb #2 there are two input tubes one is for the fuel line and there is a smaller one...??? what is that one supposed to hook to. Thanks for any help I appreciate it

1. AIR FUEL screw setting
2. top fuel screw setting___???not sure the name
3.What is the small input tube for
4.Any other tips for making this bike run good

 

[vegastruckee]

Anyone...???

 

[Andy]

Can you post pics of the screws/tubes you are talking about?

 

[dirtdigger]

I am pretty sure the tube you are talking about is the bowl vent tube. But a picture would help.

 

[andyrust]

The Tube that is just in front of the fuel inlet on the #2 carb is just a vent to atmosphere. On the 78s i believe they used a fuel screw just to the front of the bowl. I usually set it at about 3 turns out. I think the top screws you may be referring to is just a port to plug in a carb synchronizer and it should be tight so it doesnt leak air into the intake.

 

[Lechy]

A/F screws, screw them in gently until they just bottom out then back out again 2 1/2 turns. The best way to balance is by the "U" tube manometer. You will need 2 x 5mm adapters, about 15ft of clear plastic hose a broom handle and some 2 stroke oil. make a "U" tube by tying the hose to the broom handle suck up about 18" both sides of 2 stroke oil into the "U" tube, hook up to carbs 1 & 2, balance them together, carb 2 is the benchmark. Next balance carbs 3 & 4 then balance the 2 banks by hooking up to carbs 1 & 4.

 

[mycb750]

Did you bench sync your carbs? How are your rubbers? If they are really hard you may have trouble getting a good seal.

 

[Stabler]

+ 1 on the 2 1/2 turn out on the A/F screw. Bench sync. Any mods? Check coloration on plugs and adjust needles/mix screw accordingly. My .02