1970 Super Rat- Carb Woes

[bens4X4]

Hello all-
I have finally gotten a chance to put my Super Rat together. I ordered a carb rebuild kit for a Model 93(not 93A or B) a few months ago and just got it out. After taking apart the carb, it became apparent that the kit didn't match the carburetor. Inspection of serial numbers show that the engine and frame both correspond with a Model 93 and it isn't just a swap- or maybe it is.
My uncle, the previous owner, got it back from the shop many decades ago after they had put in a larger piston. It's possible that the carb was upgraded as well? I can't really find any identifying info on it so here's some pictures so you guys can point me in the right direction.

[matt glascock]

That is a Mikuni VM carburetor. A shot down the venturi would be nice for further identification. If you have a decent caliper, measure the bore. That will determine what you have and the rebuild kit you'll need.

[Al Harpster]

My two cents: this does not look like the stock VM 24. The bowl looks wrong to me.

If you'd like the workshop manual for the iron cylinder Super Rat that shows the stock carb exploded view please email me.

aharpster at copper dot net

[Tether]

Doesn’t look like a Super Rat top end to me. Didn’t all the Rats have the 4 stud intake?

[Tether]

I now see the 4 hole intake in the Other photo.
Is that a reed valve setup? That might explain a different carburetor.

[Bullfrog]

Can you give us either of the diameters indicted on the photo?

. . . and while it may not help (but it might) show us a photo of the throttle valve (slide) and pilot jet and the floats.

. . . and further - which may not help (but it might) - what is the needle designation? (stamped on the shaft of the needle)

Ed

[bens4X4]

Can you give us either of the diameters indicted on the photo?
MysteryCarb copy.jpg

. . . and while it may not help (but it might) show us a photo of the throttle valve (slide) and pilot jet and the floats.

. . . and further - which may not help (but it might) - what is the needle designation? (stamped on the shaft of the needle)

Ed

The intake manifold side measured 30mm and the top of the throttle side was around 33mm.

I now see the 4 hole intake in the Other photo.
Is that a reed valve setup? That might explain a different carburetor.

It does indeed have a reed valve intake.

I attached a bunch of pictures for what everyone asked for. Thanks for the help everyone

[Al Harpster]

I'd say that's not a stock VM 24.

I believe that's why your rebuild package isn't working out for you.

Since the bowl gasket isn't torn I'd be inclined to give it a total clean & re assemble.

A total clean would include the pilot jet and all the little holes & passages in the carb body.

This way you won't have to find & buy a flange mount VM 24. I believe they are rather rare.

[Bullfrog]

Well, it is clear that you do NOT have a 24mm carb - which was the stock size on the 93 Rat. That appears to me to be a 30mm unit (but possibly a 28mm). The appearance sure makes me think it may be a Combat Wombat 28mm unit. My recollection is that the engine side carb throat on the CW is about 29.5mm (at the gasket surface) . . . and slides are green anodized aluminum with a diameter of 31.46mm.

The needle designation for a 24mm Rat carb starts with the number "4". The stock flange mount 28mm carb from the Combat Wombat has a needle designation which begins with the number "5" - and 30mm Mikunis of the era also used a "5" needle. 32mm VM Mikuni carbs have a needle designation which starts with "6".

Ennnneywayeeee, it is clear that you do not have a stock 24mm carb there - just not sure yet what it is you DO have.

Ed

[dirty_rat]

That is not a Super Rat 24mm carb. if it is measuring out at 30mm on the manifold side. (Might be a 28mm bored out or a 30mm). The cylinder also doesn't look like a Super Rat cylinder as it only has 2 studs for mounting the carb (the reed valve has 6 holes, the top and bottom 4 for mounting to a Super Rat cylinder and the middle 2 for mounting to an Ace cylinder.) Regardless, it was ported for reeds so it should perform well as long as it was ported correctly. Further, the head looks like an Ace head as the super rat head extends out from the cylinder and the head in the photo is same size as cylinder,

Check what jets are in the carb and it might give a better indication of what carb it is and what parts you might need to rebuild it.

[dirty_rat]

I'm inclined to agree with Capt. Eddie, it looks like a 28mm carb from a Combat Wombat. The photo of the needle jet shows a O-4 needle jet, which is what came in the Combat Wombat carb.

[Al Harpster]

The carb you have, whatever size and origin, looks okay.

If you are confident it ran before I'll bet it'll run now.

Clean everything, pay special attention to cleaning the pilot jet and all the little holes in the carb body. Then put it together.

I suspect the boys are right.

That's a modified Ace engine, not a Super Rat engine.

Again, if you want the Hodaka Shop Manual in .pdf form to verify these various claims you need only email me.

aharpster at copper dot net.

P.S. I've had this Ace 100 engine apart so many times I'm embarrassed to even mention it. Carbs? I've used three.

Good Luck.

[bens4X4]

I'm still trying to get in touch with my uncle about the history behind this bike. I know he wasn't the original owner but definitely spend some time and money on it and would know anything about it.
If it means anything else, ACE 100 is on the other side of the trans case. I know they used the 100 engine in the Rat though. Thanks for the help everyone, probably just gonna try and put this thing back together and see how it runs. I have soaked it in chem dip and sprayed everywhere with carb cleaner and then compressed air.
I have a friend with a Combat Wombat I'll talk to and see if we can compare carbs.

[Bullfrog]

There is an article in the "Resonator Revisited" which walks you through the Mikuni carb - with special attention to the pilot circuit passages. It could be helpful.

Ed

[viclioce]

Looks like my VM28 carb from a Combat Wombat, guessing based on the bowl & float types. Victor