Machining Project: Boring VM26 Carbs To 29mm

the fixture in the lathe has clearance for where the boot attaches and it bolts directly to the flange. Then I clamp the fixture in the chuck.

Good thinking! If you clamped on the casting directly, you might get an egg shaped bore since those bore walls get pretty thin by the time you get to 29mm. Seems to me that most CNC lathes don't allow you to turn the chuck pressure too far down. I like how your jig eliminates that problem. Nice work. I might try this on my old 26's sometime in the future. It would be nice to compare them to my 29's that are on the bike now.

dshelly wrote: After machining you have to raise the needle to the bottom clip . Since now the slide sets lower in the bore, otherwise it will be way too rich. So what do you guys think?

Very nice job but surely you mean way too weak ?

Raising the needle richens

great job. why didnt u start with 28's? are they harder to find ?

You're right zed1015 way to weak. Since the slide drops down .07 you have to raise the needle to compensate. Yes, mark1122 the 28's seem to be harder to find and more money. You can pick up a set of 26's on Ebay pretty cheap.
I did forget to mention that the set I show in the pics was bored out to 29.5mm . That's the biggest you can go, there just isn't enough material to go any larger. The wall thickness around the flange gets too thin and when cutting the bottom you don't want to punch through into the bowl.

WHat sort of tool are you using on the mill here?

How did you decide to deepen the groove as opposed to modifying the slide?

Nice Work!

notaduc wrote: WHat sort of tool are you using on the mill here?

How did you decide to deepen the groove as opposed to modifying the slide?

By just machining the body only eliminates having to mess with the slide. However since the slide goes down farther in the body , you have to move the clip to the bottom notch. This raises the needle close to where it was to start with before boring.

dshelly wrote:

notaduc wrote: WHat sort of tool are you using on the mill here?

How did you decide to deepen the groove as opposed to modifying the slide?

By just machining the body only eliminates having to mess with the slide. However since the slide goes down farther in the body , you have to move the clip to the bottom notch. This raises the needle close to where it was to start with before boring.

By the way, the cutter is "top secret". I do this for a living you know.

Nice job

I do this for a living too...

Interesting reading about the bored-out carbs, but have not yet tried them.

www.wgcarbs.com//index.php?option=com_co...view&id=14&Itemid=29

Scroll down to "Mikuni VM30 Performance Special"

Good Fortune!