• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

VM 26/28 air jet confusion

Agemax

Agemax

Forum Guru
ok, finally finished cleaning/dipping/rebuilding the VM28's i bought for my GS.
during final inspection before fitting i have noticed a peculiarity!
on the intake (air filter) end of the carbs there are 3 holes, 1 at 2 oclock, 1 at 4 and 1 at 8.
the hole set back at 2 oclock i know is to do with the choke. on the other 2 there appears to be a jet in 1 of them.
carbs 1 &2 the jet is in the 4 oclock hole and carbs 3 & 4 the jet is in the 8 oclock hole. is this correct and if so what is its purpose?
the 26's i removed have the same 3 holes but no jets in any holes.are they supposed to be there or is it a mod specific to the 28's?
 
Pics would help, but if I follow your clock hand directions, those ports sound like the air pilot passages on my VM26s.

From the fiche:

06.gif


The air screw is actually un-numbered, but appears on the right most carb in the diagram and goes in at about 2 o'clock.
 
Last edited:
these are the 3 holes i am referring to. this is no.3 carb and you can just make out the jet in the 8 oclock hole
100_1369.jpg
 
I don't know much about them except they look just like my friend's 28's from the UK.
 
Does the VM28 have a pilot fuel screw like the VM26? Looking at that pic and your description of the jetted hole positions, it sounds like each ties into the fuel line entry point. They are on the inside face of each carb, right near the spot where the fuel line enters the carb body. The hole on the opposite side ties into the pilot air screw, as you can seen in the pic.

Perhaps they are part of the pilot system and serve as the pilot fuel jet?
 
Have you shot some carb spray into the jetted hole to see where it goes?
 
Still thinking it's part of the pilot system somehow. The passage feeds air (and maybe fuel) into the main jet and bypasses the throttle slide, just like the air passage that runs by the pilot air screw. Of course, the main jet is isolated within the throttle slide, so I don't really fathom how adding fuel/air into that part of the carb does anything when the throttle slide is low/closed.
 
there must be a tiny passage that connects into the emulsion tube. that would explain how it comes out the main jet. just checked the 26's and they dont have any threads in the holes so obviously not meant to have these jets.
maybe its some kind of boost jet to allow a bit more air/fuel mixture into the carb if you open the throttle quickly??????
 
stripped out 1 carb again and there is indeed a small orifice that feeds the emulsion tube from the tiny air jet. whether it is just air or air and fuel i cannot tell
 
anyone know if you can alter these little jets? cant find part numbers for them anywhere. there is no number on them to state what size they are.
just wondered if they are "tunable" same as mains and pilot jets etc, to compensate for a tuned set up
 
You must log in or register to reply here.
Back
Top