Differences between VM26 carbs for GS850 and GS1000 engines?

[bgk]

I have a 1979 GS1000L. Some time ago, I traded parts with a fellow GS Resources member and I obtained a spare set of VM26 carbs that came off a 1979 GS850G.

Another fellow GS Resource member is currently rebuilding and rejetting the spare set of carbs for me. The rebuild project includes a Dynojet Stage 3 kit for my 4 into 1 pipe and individual K&N pod filters (Dynojet part 3304), plus all new gaskets and float valve assembly (K&L) and new O-rings (Robert Barr).

My bike is in Massachusetts. The spare set of carbs is in California. It?s a real pain in the ass to walk back and forth to compare between the two!

The question is:

What, if any, differences are there between the stock VM 26 carbs for the 1979 850 and 1000 engines that I need to worry about (other than the stuff that will get replaced with the Dynojet, K&L, and Robert Barr kits)?

Can somebody possibly with experience with VM26 carb applications for both GS850 and GS1000 engines post back to me on this?

Failing that, can anybody with a factory manual for a 1979 GS850 post the carb specs from the manual, so I can compare them to the carb specs in my GS1000 manual?

Finally, anybody have a spare ?T? fitting from the fuel line into the carbs that you?d be willing to sell me? It?s a metal ?T? with rubber coating on the ends. My ?T? fitting is a little loose and I?m worried it might leak fuel some day in the future.

Thanks.

[earlfor]

Re: Differences between VM26 carbs for GS850 and GS1000 engi

Brion, as far as I know, all GS 1000's up to and including 1979 used VM 28
carbs........not 26's.

Earl

I have a 1979 GS1000L. Some time ago, I traded parts with a fellow GS Resources member and I obtained a spare set of VM26 carbs that came off a 1979 GS850G.

Another fellow GS Resource member is currently rebuilding and rejetting the spare set of carbs for me. The rebuild project includes a Dynojet Stage 3 kit for my 4 into 1 pipe and individual K&N pod filters (Dynojet part 3304), plus all new gaskets and float valve assembly (K&L) and new O-rings (Robert Barr).

My bike is in Massachusetts. The spare set of carbs is in California. It?s a real pain in the ass to walk back and forth to compare between the two!

The question is:

What, if any, differences are there between the stock VM 26 carbs for the 1979 850 and 1000 engines that I need to worry about (other than the stuff that will get replaced with the Dynojet, K&L, and Robert Barr kits)?

Can somebody possibly with experience with VM26 carb applications for both GS850 and GS1000 engines post back to me on this?

Failing that, can anybody with a factory manual for a 1979 GS850 post the carb specs from the manual, so I can compare them to the carb specs in my GS1000 manual?

Finally, anybody have a spare ?T? fitting from the fuel line into the carbs that you?d be willing to sell me? It?s a metal ?T? with rubber coating on the ends. My ?T? fitting is a little loose and I?m worried it might leak fuel some day in the future.

Thanks.

[focus frenzy]

agreed, the 1000 uses bigger carbs than the 850.

[KEITH KRAUSE]

Not so you guys. In the U.S. at least, only 26mm were installed. I believe Australia or other countries had 28mm installed.

[SqDancerLynn1]

MY BOOK GS1000E lists the carbs AS 26mm for the GS1000 and 850 Other than a main jet difference they are the same, if you are installing a jet kit It doesn't matter The 850 is jetted richer than the 1000

[KEITH KRAUSE]

MY BOOK GS1000E lists the carbs AS 26mm for the GS1000 and 850 Other than a main jet difference they are the same, if you are installing a jet kit It doesn't matter The 850 is jetted richer than the 1000

Lynn, just curious. If you have the carb spec's for both the 850 and 1000, are you saying the only difference you see is the main jet? So, in particular, the air jet and needle jet are identical? That's needle jet, not jet needle.
I have the 1000 factory manual spec's but not any technical 850 info. Thanks!

[earlfor]

This is getting a bit strange. I have recently rebuilt and tuned two GS1000 carb sets. One was a 78 E model and the other was a 77 L model. Both had 28 mm VM carbs.

Earl

MY BOOK GS1000E lists the carbs AS 26mm for the GS1000 and 850 Other than a main jet difference they are the same, if you are installing a jet kit It doesn't matter The 850 is jetted richer than the 1000

[SqDancerLynn1]

77GS750 NEVER came with 28mm
The info I have shows VM 26mm
GS1000 main jet #95 Needle jet 0-4 Jet needle 5DL36-3
GS850 #102.5 0-6 5DL36-2


The 26mm were sometimes bored out to 28mm and modified

[KEITH KRAUSE]

Lynn, thanks for the info.
Earl, they did'nt make a 1000 in '77. I don't know how things happen, but I'm positive about the U.S. bikes only getting 26mm carbs. That's what every factory manual I've seen says too. Also the Suzuki dealers. I've heard from a couple of members here that Australia and possibly other countries had 28mm carbs.
I'm the one who's working on BGK's carbs. He said they're off a '79 850. They look identical to my '79 1000's. In fact, they even have the same #95 stock mains and the needle clip in #3 groove which contradicts Lynn's info. Of course, someone could have changed them. That does'nt bother me because the mains/needles are being replaced anyway. What bothers me is if these really are 850 carbs, then according to Lynn's info the needle jets are a different size. I can't see any size stamped on them, but they look identical, same # of tiny holes and everything. I'm going to have to just hope that the needle jets are also actually 0-4 (1000) and not 0-6 (850). I don't need more jetting questions. I'm wondering if Brion was given bad info and these are in fact off a 1000.
My biggest problem right now is his fuel "T" for the fuel line. These carbs have a metal "T" with a thin rubber coating over the ends that slip into the carb fuel inlets. The rubber ends have "built in" o-rings. His is loose and after I finished his carbs I tested them and sure enough, it leaks. The part is not sold anymore and my only salvage yard does'nt have a good one. I guess the rubber shrank a little from non-use, I don't know. The rubber feels fine. I had one spare but it actually fits even worse. So we're dead in the water until we can find one that fits tighter. Very frustrating.
Just wondering, has it been your experience that after the rubber is exposed to gas for a while, that maybe the rubber will expand some?

[Anonymous]

About that 'T' fitting: Some of these carbs use all metal tubes which have grooves for O-rings. For these, there's no problem, as my kits include these O-rings. (12 total). I've had trouble trying to narrow down which years had which fuel tubes.

If you can hunt down one of these all-metal 'T's, I'd bet that they'd replace the rubberized type (with new O-rings installed, of course), presuming that the inlet bore diameters would be the same between the years. Maybe you can pull up an exploded diagram at a dealership or elsewhere, but I just can't see a manufacturer re-tool for a different diameter of inlet bore for the exact same function on the same carb. They'd have to re-cast each carb, and that costs $$$.

[Anonymous]

Aha! Found one. Look here:

http://www.motorcyclecarbs.com/mikuni/frames/VM29frame.htm

Now, these are 29's, and I have no idea if that part would fit the 26's, but at least you can print that and show your dealership parts person...

[bgk]

Thanks guys,

Yesterday, I posted on the Parts Wanted forum, looking for a replacement "T" fitting. No responses yet. I called a motorcycle salvage yard today. No luck there either. I'll keep looking and phoning.

In the meantime, I've got a dumb question:

Could Keith simply use the Robert Barr O-rings in the "T" fitting I've already got, kinda like a "press fit"?

Once the "T" fitting is installed, it doesn't move, right?

[earlfor]

I've had good luck taking things like that to the local hydraulic repair shop and they have always had "O" rings that would fit whatever I happened to be struggling with. :-)

Earl

Could Keith simply use the Robert Barr O-rings in the "T" fitting I've already got, kinda like a "press fit"?

Once the "T" fitting is installed, it doesn't move, right?

[bgk]

Hey, hey, hey!

I just checked out the link to motorcyclecarbs.com that Robert provided.

The part number for the "T" fitting (part #8 in the diagram) is VM26 / 268.

Seems logical it would be for a VM 26 carb, even if the parts diagram and list is for a VM 29.

Unless you guys tell me otherwise, I'll order the "T" tomorrow and have it sent direct to Keith.

[KEITH KRAUSE]

Brion, it took me 1.8 seconds to try using the o-rings over the existing fitting. They just roll out as you slip the "T" in. The o-rings appear to be a good fit but after you stretch them over the already rubber coated fitting, they are too big. You would'nt want a stretched o-ring in service anyway.
I think the other style of "T" with the replaceable o-rings is an upgrade. The thinner rubber coating with the raised ribs just is'nt going to consistently last unless it's in a certain environment. That's why the used ones all seem to be different diameters. Some have been in better conditions/temps' than others. Most of them, regardless of conditions, seal OK IF LEFT UNDISTURBED.
I just checked out the site from Robert. I too, would have to believe the 29's "T" would work. I would guess that Robert's o-rings in your kit would be the same too and you would'nt need to also buy the 29's o-rings, but that's just a guess. The two different styles of "T" should not vary except for the how they designed the rubber ends. Where I could see the potential for difference is in the width of the "T". I just measured it and the total width from rubber end to rubber end is just over 2 1/4". The width of just the metal body is 1 1/4". Those replacements measurements would have to be the same with just a little smaller still OK, but any wider would'nt fit unless it was very little. I could'nt figure out their site to see prices. If they're cheap, maybe it would be a good idea to just get the "T" with it's 4 o-rings? You need to e-mail them about the width first.
I'll be buying one too for future purposes if it's right.