Mikuni VM 33 Carbs

I soldered and drilled the 1.2 jets to .6 after I tried new .9 air jets when I went #20 pilots. I then redrilled them back to 1.0 with 17.5 pilots. Still a touch rich on the bottom so the 15's. I still have the .5's I made out of the .9's to try if too lean off idle.
Those are good prices.
Steve

Had a thought after examining spark plugs and checking compression...
Would #3 be lean due to lower compression in that cylinder? If so, would having a richer air jet in just that carb serve to compensate?

Might be from air getting by that manifold at the head. Will be installing a new set this weekend.

It would show rich.
Steve

Rode 80 miles today after swapping out cylinder three air jet to .5, leaving the others .6's.

Immediate improvement; smoother idle and better throttle response through the entire operation rpm range, with only a slight adjustment to the fuel screw. Hardly any pops now when letting off throttle and between gear shifts.

Will post pic showing plug condition after riding some more miles.

Little job just got larger. :dry:
Steve

This is with 17.5 pilots, we'll see what they'll look like with the 15's.
Steve

Curious how far your rubber intake boots project inside your air box on 1 and 4, and if the air flow may be somewhat restricted compared with 2 and 3

*Approximately 150 miles later #3 spark plug color appears less-lean, and more as the others:

Only about an inch. The 15's seem nice but I think I set the float levels too high.
Steve

I think I have them too high.
Steve

Always wondered what they looked like running. I'll lower them then do a running check on all of them.
Steve

Vacuum Carb Sync?

Watched your clear-tube video...cool. Hadn't thought of that. :huh:

Before installing new manifolds this week, I will do a running level test. Have floats at 18mm. and was contemplating resetting them back to 17mm. (+/- 1mm) per Mikuni spec for RS carbs.

Having one different air jet in the set significantly improved the starting, idling, and overall throttle response of my engine. Now the #3 cylinder plays a whole lot better with the others.

RS Flat Slide Smoothbore carburetors:

:woohoo: