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carb set up off the engine

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neat street:
good morning all
I have read somewhere on this forum a way of setting up the carbs  beffore putting them back on the engine?? I seem to recall that you can set the heights of the slides by sliding a small drill bit under each one to set them which i beieve was a 3mm bit? can onyone please confirm, or has a different solution please?
thank you

Laverdaroo:
No that’s the way to do it, works a treat, while youve got them off, might be handy to check if your float height skills and run some fuel through them to check for leaks, see picture.

Beats taking them on and off!


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McCabe-Thiele (Ted):

--- Quote from: neat street on August 31, 2024, 11:33:20 AM ---good morning all
I have read somewhere on this forum a way of setting up the carbs  beffore putting them back on the engine?? I seem to recall that you can set the heights of the slides by sliding a small drill bit under each one to set them which i beieve was a 3mm bit? can onyone please confirm, or has a different solution please?
thank you

--- End quote ---

IMHO 3 mm is way too much for a bench synch, on my 400 I used an odd sized drill shaft iirc it was 5/64 so a tad under 2 mm.

On my 500 I did it slightly differently as instead of a measurable gap I went for the point where the slider just started to lift/move off the bottom of the carb body. I found I ran out of thread on the main stop scew on the carb array bracket so had to build up the lug where the stop screw meets the bracket.

Certainly worth checking the carb bowls for flooding after you have checked/adjusted  the float heights using a small header tank (as per Roo's photo) Much easier than having to take the carbs off again.

K2-K6:
The diameter of drill, or similar, should have no impact other than being in range of the "master" idle screw threads to allow tickover adjustment competently after install.

If for example you just open the throttle mechanism and place a spacer underneath that screw to stop it dropping the slides, then any resulting gap under the slides can be set to parity across all four, doesn't really matter if it's 3, 5 or 10 mm there, as long as you set them the same, then take out the spacer to drop the throttle mechanism back to correct position.

McCabe-Thiele (Ted):
The advantage I believe of a narrower gap when bench setting is you can easily obtain a lower idle speed.

If you set it at 3 mm it might idle  too fast. I found this helpfull when dismantling carbs. He uses 1/8" drill shank I went for smaller.

https://www.vintagebikebuilder.com/cb350-400f-carb-rebuild-demonstration.html

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