Mikuni VM 33 Carbs

Still have to lower the floats.
Steve

Having mini heat waves again this year.
Steve

Dropped main jets from 120 to 117.5
Now wondering about 15's

:whistle:

You need to put at least 100 miles on the bike before you make any changes. You don't want to go too lean.
Steve

SWest wrote: You need to put at least 100 miles on the bike before you make any changes. You don't want to go too lean.
Steve

Agreed! The 17.5's seem good, but I won't know about the 15's unless I give em a shot. Makes sense it would run lean with 20's, but the plugs don't show lean with the 17.5's...and there is no obnoxious popping on deceleration or between up-shifts with them.

Wondering if oil burning may contribute to the engine running well with leaner jets?
Any info I've seen about jetting with a header and other slight mods does not support going lean...

:whistle:

While on the subject of big jets, I picked up a handy little Motion Pro tool that makes changing the pesky things easy when the carbs are mounted on the bike. Motion Pro stopped producing this tool around 2012, but it still shows up in their jet-tool images frequently posted on ebay, though nearly impossible to find.
View attachment

When I was fouling plugs due to old bad valve guide seals I had to drop down two steps on the pilots. Could be the same thing here only less. Still going to lower the levels 2-3 mm.
Steve

Makes sense. The base rings are showing less carbon buildup, and gas mileage is improving.

Nice having this forum available for discussion now-a days, when few bike mechanics are willing to even look at older (but gooder) bikes anymore.
If you have a little mechanical aptitude and the dedication to keep these old contraptions running, the results can be quite rewarding.

:woohoo:

Been flying around with 115 main jets for a few days, and man oh man.
The plug color is starting to look pretty good. Acceleration is like I can't even remember, and no pops in any direction.

The lean changes probably won't reduce oil consumption much, but I gotta say I am blown a way how the old engine is running now. :evil:

Seems to be cleaning up. I'll keep it this way for a while.
Steve

Things will change when I put on the new head.
Steve

Still need to adjust the float levels. :dry:
Steve

Had to reupload the clip.
Steve