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VM carb rebuild question

Wallowgreen

Wallowgreen

Forum Mentor
Past Site Supporter
So now I have my supplies, I'm well into the strip down, clean and rebuild of the VM carbs on my 79 GS850. However, things haven't gone exactly without issue to this point so here's the first of what's likely to be a number of questions I'm hoping those in the know here can help me out with...

It was my plan to keep the carb bodies as one unit on the mounting plate so I didn't have to worry about whether I had the o-ring or the non replaceable sleeve type fuel connectors. In the end I had no choice and had to split the bodies, of course I have the rubber sleeve type connectors. What's the experience of others with this, am I likely to have problems with fuel leaks now and if so does anyone have a good solution?

Thanks as always.
 
At you talking about a rubber coated T, or are the other interconnection tubes rubber coated as well? The rubber coated parts will seal as long as there are not any cracks in them and when you press them into the carb bodies there needs to be a little compression on the rubber. If they slip into place super easy, that is not good.

For my old 550 a friend turned down a tube on a lathe that will accept O-rings. After he did this I drilled a hole and brazed a barbed nipple. Worked great. Similar work could be done on a drill press if you are handy. If necessary you can purchase premade parts like this although they are very expensive. Google on Motorcycle Carbs and the shop should come up.

Picture042.jpg
 
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If you've got the rubber type as on the right photo you can try some o-rings as described in this thread. Interesting though, as I've just had my carbs apart the rubber over time has some how rejunvinated itself and the fittings work just fine by themselves now. When first installed the o-rings my carbs had been apart for quite a while and maybe the fittings just dried out from sitting. If they were a tight fit when you took the carbs apart maybe they are OK. If it's going to be a while until you get them back together maybe store them in a container with gas or coat them fork oil to keep them moist. Fork oil has a rubber conditioner and preservative in it. I just noticed it's been 3 1/2 years since I did this and not a drip from the carbs.

http://www.thegsresources.com/_forum/showthread.php?t=79717&highlight=fitting
 
I didn't have any leaking on either of the two sets I dipped.

Just don't dip that T connector!
 
Z1 Enterprises sells a T fitting for Kawasaki applications. The width of the T looks kind of narrow though for Suzuki applications so you should call them to get the dimensions before ordering.
 
Wow! I was just gonna ask you guys about this little T fitting! I was handling my carbs the other night getting ready to put things back together and found that there was so much room that the T was actually loose in the holes. I couldn't remember if it had leaked before or not, but I know that something was leaking in the carb area. Now that I think of it, it was likely that fitting. Will definitely try the brass fitting in the drill press idea and let all know how it works. I've made parts in my poor man's lathe like this before. ;)

I think the T is much the same as my XS650 as well which is the O ring type.
 
Yep, those are the ones. It says in the rebuild notes that they can be troublesome when disturbed but I think mine feel like they are tight enough to seal again, I'm going to try that anyway. As for turning little brass tubes to accept o-rings, boy I wish I was that good working with metal. Sadly I'm an electrical engineer so have little chance.

Just put carb #1 back together as I found it but have another question. In the notes it shows the pilot fuel screw inside the bowl has a spring with it. I didn't find one in the carb I've just done so of course had to put it back together without one. Don't know about the others yet. What's the opinion about that? I looked on the parts fiche and of course you can't get them.

Also, the pilot air screw on the outside only took 1/4 turn to bottom out from where it was set originally, not sure what to make of that. I've turned it out 1 1/4 turns to start like the notes say.
 
The fittings I used the o-ring fix on doesn't look like at all like the one in Nessium's photo. The T I have is much wider (from a GS1000) is made of cast aluminum with a rubber coating where it goes into the carbs. It also has a wider flange that butts up against the carb that allows the o-ring to seal against the carb body.
 
Wallowgreen said:
As for turning little brass tubes to accept o-rings, boy I wish I was that good working with metal. Sadly I'm an electrical engineer so have little chance.
Click to expand...


I'm an Electrical Engineering Technologist and I build all kinds of things on my own. Just because of what your day job is doesn't mean you can or can't do something. You don't need fancy or expensive tools to make simple parts that look professional. Those tools were invented to make things easier and faster (more efficient).

I've done rattlecan paint jobs that Pro body guys jaws dropped when they saw them. I've made mechanical stuff that Pro machinists have looked at and asked how the heck I did it and what kind of fancy machine I used for it. Simple garage tools my friend, and a lot of patience and time. The beauty of the garage projects is that time and efficiency aren't usually an issue. You can do things the most ridiculous way and take 100 times longer than the pros would, but you get it cheaper, you get the experience, and the satisfaction of a job well done by yourself. Oh, and the knowledge that next time you'll definitely do it MUCH differently. :D

Moral of the story: Don't say you can't until you try. And don't let anyone else tell you you can't either.
 
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Wallowgreen said:
Yep, those are the ones. It says in the rebuild notes that they can be troublesome when disturbed but I think mine feel like they are tight enough to seal again, I'm going to try that anyway. As for turning little brass tubes to accept o-rings, boy I wish I was that good working with metal. Sadly I'm an electrical engineer so have little chance.

Just put carb #1 back together as I found it but have another question. In the notes it shows the pilot fuel screw inside the bowl has a spring with it. I didn't find one in the carb I've just done so of course had to put it back together without one. Don't know about the others yet. What's the opinion about that? I looked on the parts fiche and of course you can't get them.

Also, the pilot air screw on the outside only took 1/4 turn to bottom out from where it was set originally, not sure what to make of that. I've turned it out 1 1/4 turns to start like the notes say.
Click to expand...

I think that you are confusing the pilot mixture screw outside the bowl(which does have a spring), with the pilot jet inside the bowl , which doesn't.
My '79 850 pilot mixtue screws are the originals and are set at 3/4 of a turn off the seat. I run a bigger pilot jet than stock, but still find this factory position works the best. The pilot air screws are set at around 1.5 off the seat.

After cleaning my carbs, the Tee was a loose fit after sitting for some weeks. They seem to dry out. The point is, I had a slight leak there when I first filled the carbs. All I did was swivel the tee back and forward which allowed the fuel to swell the rubber until it sealed. It hasn't leaked since, and there is real resistance to swivelling when I try that now.
 
Big T said:
I didn't have any leaking on either of the two sets I dipped.

Just don't dip that T connector!
Click to expand...

ditto, but mine don't fit real tight and still don't leak.

If I leave the carbs sit empty, either on or off the bike, then fill them with fuel, they drip for about five minutes, then stop.. Figuring that out took months... I'd pull the carbs to rejet and maybe not get them back on right away.. put them on and fuels leaking off the bottom bowl. Start to look for leak and it stops...... WTF??? pull the carbs a few weeks later.. Same problem...I didn't figure out what was happening until the fourth time when I had the right angle to see fuel dribbling out of the connection...
 
Rudy, there's a reason I'm an electical engineer... out of all the materials on the planet, metal is my least favorite to work with is all.

49er, I've now taken carb #2 apart and there is a spring with the pilot fuel screw in that one so either I couldn't dig the one out of #1 or it was missing as I suspect but I'm sure it is the pilot fuel screw.

As for the last guy to work on these carbs, the o-rings I'm replacing are definitely not the correct ones, some are vastly over sized. All seems to be going ok at the moment though.
 
I just used some teflon tape to seal the transfer tube on an old holley carb, wrapped it right around the o-rings, shoved it in and it sealed up tight as a drum.

Not the preferred technique, but it was cheap and didn't require a trip to the parts store. Times are tough, do what you gotta do...;)
 
All are back together except the choke plunger from #4. The plastic collar had a part of it almost broken off so right now it's sitting on the kitchen window to let the epoxy dry in the warm. I didn't rush the job and all seemed to go ok.

All nice and clean:
View attachment 5425

Now to move on to installing them back on the bike and setting them up. I wonder if it'll ever run again?
 
I have an extra choke spool you can have, drop me a PM if you want it. I also should have some extra fuel screw springs if you are in need.
 
Mark Harrop said:
I just used some teflon tape to seal the transfer tube on an old holley carb, wrapped it right around the o-rings, shoved it in and it sealed up tight as a drum.
Click to expand...
I have done that to more than one set of carbs, too. Works great, price is right. About 5 or 6 wraps seem to do the trick.

.
 
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