Keihin VB 52 Parts Diagram

[johnw]

Hi there, does anyone have a source for a detailed parts diagram for the carbs fitted to my 1980 Japanese market Cb750c.
They are marked VB52
There are some parts missing from carb 2

 

[amc49]

https://boldorclub.nl/wordpress/wp-content/uploads/2015/01/honda_carb_manual_revf.pdf

Partzilla.com

 

[tenko750]

Please can anybody say how many turns out from fully in should the pilot screws be on the VB52A carbs ? The UK or Euro carbs without the accel pump (CB750KZ). Also if no accel pump fitted, will any fuel at all get to the accel pump gallery at the back of the carbs, or is this gallery isolated from the fuel ?

 

[elcochinato]

Hello, 1.5/2, to start... Then you normally open between 1.5 and 3 turns. No more than that. If you need to open more, be sure there's a clogged duct (try a larger jet on the low-end jet, it might be worth it). If the jet screw is on your carburetors on the intake side, the more you open, the more air the mixture will have at idle.

If it's on the air side, the more you open, the more air the mixture will have.

The jets only work at idle. If you fail above 1,500 rpm, the issue lies elsewhere.

The carburetors are over 40 years old, it won't be easy (clogged ducts, enlarged sprinkler tips, etc.). Trial and error, my dear friend. I've been here for a year, but I have the VB42s.

So let's keep experimenting together. I'll be active on this forum.

Good luck with it and have a good trip... when you're on the road, haha.

Translated with Google Translate

 

[tenko750]

Hello and thanks for the reply. I have since found a page from the official Honda manual and I think this is for the VB52 carbs.

My initial pilot setting is 1 1/2 turn out from fully in.

1. Warm up the engine to operating temperature.
2. Attach a tachometer (use rev counter ?)
3. Adjust the idle speed with the throttle stop screw to achieve 1000rpm +/- 100 rpm
4. Turn each pilot 1/2 turn out from initial setting
5. If engine speed increases by 50 rpm or more, turn each pilot screw out by a continual 1/2 turn until speed drops by 50 rpm or less.
6. Adjust the idle speed with the throttle stop screw.
7. Turn No1 carb pilot screw in until the engine speed drops by 50 rpm
8. Turn No1 carb pilot screw 3/8 turn out from the position obtained in step 7
9. Adjust idle speed with the throttle stop screw
10. Perform steps 7,8 and 9 for the 2,3 and 4 carb pilot screws

Phew, maybe rev counter is not accurate enough to see 50 rpm changes ?

Best of luck

 

[elcochinato]

Hi, yes, that's the way it is. Only for new carburetors... With these older ones, use that technique, but the revs won't be the same. I recommend a digital tachograph. The one on the motorcycle isn't very accurate.

Translated with Google Translate