strange carbs

[tomale]

In recent days I have come across a couple kind of strange Carbs. I saw a Bultaco with a Bing carb that had a mikuni style choke lever and no tickler. That has to work better. When I asked I was told that the later model of Bings were like that. That was nice to know.
The second is a very odd Mikuni. It looks normal in all respects except that there is a hose running from the bottom of the float bowl to the top of the ventury. Terry had bought it off E bay he said it had come off a Penton. What could that hose be for? It is not a float bowl vent those hoses are in place too. Is it for some other application? like maybe a airplane motor? does it effect the air/fuel mixture at higher altitudes? Any ideas.

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[firstturn]

Thom,
  If you have time email me a picture.  I have helped people with carburetors that I had to put vents in the float bowl to help with enormus changes in altitute that involved several thousand feet changes(allows pressure to equalize faster).
  I did get you phone call at Mid-Ohio for springs, but I didn't understand your measurements you left me i.e. 13 1/2 shocks or 13 1/2 springs??   Sorry.
[email protected]

Ron Carbaugh

[farmer58za]

Hi Thom
I have a bing like that - came off a '77 KTM I'm told.

The Mikuni with the pipe is a "power jet" type. They were used on some IT Yamahas. The IT175G and newer models used them. Where the pipe goes into the venturi, there is an additional main jet which meters fuel at full throttle only. The main jet inside the carb is smaller than in a normal type carb.
The aim is to allow the bike to run cleaner at part throttle whilst allowing a richer mix at full throttle to avoid high speed siezure.

regards

Regards

David
'75 KTM GS250
'75 KTM GS400

[firstturn]

David is correct if that is the style carburetor you have.

Ron Carbaugh

[tomale]

Ron, that sounds plausable to me. I just took some pictures of the carb and will try to send them to you. I am not very puter literate. My wife had to drag me into the last quarter century, with me kicking and screeming. I would rather do just about anything than try to figure out how to send stuff. I seem to mess things up, so we will see. here goes!

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[bildough]

Tom;
  you are much better wrench twister and rider, than a keypuncher

bill cappel

I ride several Tom Green wrenched Pentons

[hrbay]

I think a power jet Bing was used on early 80's 495 KTM's and are hard items to find, or so I was told by a 495 racer and sage on these particular bikes.

GC

[firstturn]

Tom,
  I am going to answer your email and the viewing of the pictures on thr Forum so everyone can follow the story line.
  I think this is a very early power jet Mikuni.  I used some of the power jet arrangements on my modified outboards.  I think this is a early one and the 495 story may be valid, but I never raced one.  I will check with the Big Boy over in East Texas that still ride these monsters to get their take.  Good question.


Ron Carbaugh

[tomale]

Thanks Ron, as I told you on my e-mail, it may not be a big deal. On second thought it could cause a bit of a problem in rejetting if in deed it is an early Powerjet. Just when I thought it was safe to jet again. This had to be thrown in...
Thanks, it is better to assume that you do not know than to assume you do and assume wrong. [8D]

By the way the 13 1/2 was the shock lenght. And I need them to fit Marzokes shocks and for my weight(245). Hey I am loosing weight... I have already lost in the last year, 15 pounds.... The stock spings were terrible. I felt like I was ridding a chopper. The sag must have been 4 inches.

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.