VM20 carburetor question

[Tether]

Can anyone tell me is this carburetor will work on the Ace 100?
https://www.summitracing.com/parts/mku- ... plications

[taber hodaka]

sure looks good to me, We have adapted many over the years. I could be a bolt on bolt on without modification. --------Clarence

[Al Harpster]

The key here is the bolt "spacing".

I believe THIS modern carb has spacing of 50mm. And is slotted for an 8 mm diameter bolt/threaded stud.

As I recall the bolt spacing on the Ace manifold is 40 mm, and is using a 6mm diameter stud.

Someone on this site said he'd worked up an adapter. But I've never seen one or even a sketch of one.

If somebody has a sketch I'll try to machine one.

My previous attempt resulted in zip, nada, couldn't figure a way.

[JPark]

I think it is actually 39mm. And I squandered a few hours coming to the same conclusion.

I think Hodaka-Parts has a manifold available that fits a 22mm Mikuni but it's for the clamp on spigot type, another blind-ish alley.

You could make a plate with a 22m hole - that's what the original is - and just weld it to the manifold. Two 8mm studs and you're done. You do have to take into consideration that the weight of the carb is cantilevered out from the manifold and being vibrated so it can't be JB weld....well it could be, for a while. I love long walks in the woods, but not pushing a 180 lb bike.

While going from 20 to 22 mm sounds like only 10% bigger, it's actually 21% more area. There's a 22mm Mikuni with the same or similar chassis dimensions as this new 20, I think ??, that 's readily available. I always felt that the Ace 100 could use a bigger carb for road and race work but maybe that Ace 90 carb was the rev limiter that made them durable.

Although it' s been a while, I think Jets-R-Us has a selection of Mikuni carbs and the dimension specs for them.

[JPark]

https://www.jetsrus.com/carburetor/carb ... eries.html

[Al Harpster]

With time and money all things are possible.

The 22 mm spigot adapter for $30 could be a start.

Maybe a flange for the VM 22 could be milled and brazed on to the spigot mount with these new low temperature aluminum brazing rods from harbor freight or bernzomatic.

OR..... a Hodaka reed manifold, skip the reeds. Drill two holes for the 6 mm studs because most are for the 4 bolt iron rat. I know the 22mm VM will fit that rig.

But those are rare and tall dollars.

[JPark]

I'm thinking that a flange mounting plate drilled to go over the 22mm spigot adapter could be made in numbers and then bonded to the spigot with epoxy. That kind of epoxy sleeve system holds really well even with hardware store epoxy.

I wonder what the supply is of those manifolds? A nice job would require a milling machine and a bandsaw, but a drill press, hacksaw, and time on your hands could do it.

I'm getting interested, especially given that it doesn't involve doing any injustices to original Hodaka parts.

[viclioce]

While we are asking VM20 questions, what’s the best way to pull a frozen & stripped pilot jet? I already tried boiling the carb in pinesol. No luck. I’m trying to strip down 2 carbs and make 1 usable one. But they both have pilot jets which do not want to come out. Victor

[JPark]

By stripped I assume you mean the screwdriver slot. I have a specially ground screwdriver that fits the slot perfectly and I've always managed to break them loose, but if you're late to the party or they're just bonded in, I'd try drilling the center out being careful to only go in through the threaded end and not down to the taper region and into the carb. Then you can take the next size larger drill bit and grind it down so that you can wedge it into the hole and then unscrew it. An 'easy out' that small could be tough to find.

I was just about to tear down a VM20 so I could give you the dimensions of the jet and the appropriate drill sizes if you'd like. I'd practice on the scruffiest of the two bodies...

[viclioce]

Have you tried a left handed drill bit for the pilot jet? Victor

[JPark]

A 5/64 left handed would be about right and a 1/8 would pass inside the threads. Drilling a 1/4 " down will get you as far as you need to go.

Using a custom tapered 1/8 LH bit as an easy out would be better than a RH, but wedged in and some downforce on it, a RH might do it anyway. Usually just removing most of the adjacent metal frees the threads enough. Once you've drilled into the tube part with the taper there's less reason for it to stick. The emulsion tube is 3mm OD so if you just go through with a 1/8 there's not much wall left and the compression is relieved.

The thread appears to be 5 X .8 mm - very convenient.

[Tether]

I still have my modified screwdriver that I made about 1976.