Mikuni VM - setup - does not take more than 1/4 throttle

Have you R&R points & condenser, sparkplug? Did it run fine last Fall? If
not carburator, then crankcase seals could be leaking, how long since bottom
end rebuilt? Never? broken reed ?? more info needed for cyber tune...

 

Forgot top end , how long since top end? how many # compression?

 

Thank you very much to all of you who contributed.

Yesterday, I went through the hazzle and took the carb out again (this
time removed the entire air box with the (way to hard) plastic boot
connection the carb to the box.

In short, the problem is solved, the bike runs great.

Here is what I found:

1) My VM carb has indeed NO air adjusting screw. I compared the Suziki
parts manual with the exploded drawing of the carb with the one I
downloaded from the link given in this thread! I took pics of the carb,
but don't know how to post them here to show the carb (and the Suziki
drawing/parts list). Let me know if/how I can post the files here.

of the needle jet and is lying in the float bowl.
I actually had this happen once. I was trying to pass an 18-wheeler and

when I tried to use full throttle, the excess full coming through the
needle jet was drowning the engine. <<

Well guys, this is exactly what happened; when I took the bowl off, it
was right there. I put it in an tightened it poperly, put the carb back
on, and ... boom. Starts with first kick, run like a sweatheart. Thanks
FB.

The only thing left to clearify is really: what kind of carb do I have,
if it does not have the air mix screw.

Volker

 

Nice result all round.

 

Google doesn't allow posting of binary files.

But I looked at the 1980 TS125 Duster carburetor diagram at
www.partsfish.com.

You can go there to look at diagrams or you can use www.bikebandit.com

The pilot air screw isn't actually shown on the diagram, but I suspect
that if there is a pilot air screw, it is hidden underneath a blind
plug on the right hand side of the carburetor, the same side the idle
speed adjuster is on.

If there is a blind plug there, it would probably be in a part of the
carburetor body casting that is at a 45 degree angle to the center axis
of the carb. The blind plug would be there to keep owners from
tampering with the idle mixture and polluting the air.

If there is no blind plug, it may be that pilot air flows through a
fixed orifice. That would make tuning the carb for operating at high
altitude very difficult.

I also remember that Suzuki was claiming that they were using "altitude
compensating" devices on their carburetors during the 1980's. But I
never pursued the
issue.

 

I told you it was either the needle or the needle jet, that was all it
could be if it was cutting out at 1/4 throttle.

Leon

Leon

 

Posting binary files on Usenet is a no-no. Put them on a Web-site
somewhere and post the URL.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

FB, I sent you 2 photos of the carb, and there may indeed be a 'hidden'
screw.
Let me know what you think.

I got my diagrams also from bikebandit (great source for parts info).

Volker

 

Well, posting binary files to a non-binary newsgroup is a no-no. Of
course, since Google doesn't deal with binaries at all (AFAIK), and many
news servers don't cary binaries groups at all, it's typically easier
for everyone if you host the files somewhere (e.g. flikr, shutterfly)
and post a URL rather than posting to e.g.
alt.binaries.pictures.motorcycles

fwiw

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

Glad you got it going. You just saved yourself 15 bucks for a book and
45 dollars an hour to have someone fix it for you, plus you now know
how to clean your basic 2-stroke carb....