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VM26SS Carb re-build on GS850G

  • Thread starter Thread starter Guest
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Guest

Guest
Firstly, hello to you all from lock-down UK

Since I had more time on my hands recently, I picked up an old '79 GS850G. On first ride out it's 3rd cylinder pipe was cold so I figured since I wasn't doing anything, it would be prudent to clean the carbs and check the valve clearances.

I'm not a professional but I like to have a go 'cos when you're on the trail.... who you gonna call?

Carbs all sonic cleaned but can anyone give me a ball park for getting the mix right before initial start up? (for example: 1 turn on the air screw, 1.5 on the fuel screw) and with these '70's plungers, is it best to set them identical on the bench first?

I hope that there are enough people in love with these bikes that they have done this too and can give me a steer. I got my carb balancer, this is just so I can get a "fire up" to tweak after install.

Cheers fellas.
 
If the airbox and exhaust are stock, set the fuel screws (the ones on the bottom) about 3/4 turn out from LIGHTLY seated. Note the emphasis on LIGHTLY. The tip of the fuel screws will break off VERY easily and wedge into their holes, blocking any fuel flow.

As a general rule, the air screw will be double the fuel screw setting, but for starting up like you are doing, I like to start richer, then lean it out from there. Start with the air screws (the ones on the sides) about 1 to 1 1/4 turns out.

Yes, it does make sense to do a "bench sync" to get the openings close to the same. My favorite method is to hold the carbs up to a light and observe the sliver of light under the slides. Use the idle speed adjustment screw to a minimum setting, then use the individual adjusters to get them close to the same.

.
 
Afternoon Pasty...which bit of lovely sunny Cornwall are you playing in? I have a '78 GS750 with VM26 slides (sshhhh I also have pods and a 4:1 exhaust) and can probably strip and re-assemble the carbs in my sleep.

I'm over here in ever so lovely Plympton.
 
Thanks Steve, that's a great start. Yes, air box standard and 4 into 1 Motard exhaust, which is apparently quite restrictive but i'll get the old girl happy before I start fiddling with her bits. (The bike that is!) Cheers man.
 
Geddon!! I'm in Par; or 'Parbados' on the south coast. Yeh, so i bought this during lockdown and had her couriered. On first ride out i noticed no3 pipe was cold. Know the old guy I got it from had the carbs out to get the float levels but they didn't look clean and there was all kinds of paint overspray in the tank so... in we go. Shims ALL tight apart from no3 exhaust which was floppy. Made me question myself but trusting in science, i've bought smaller shims to install, then it's carbs on, then it's balancing up. All pretty new to me. I got the clymer book for the basics but knowing that you'm a bit of a veteran at this and on this forum is really cool!
It's hard not to love the engineering of the late 70's Jap bikes and this GS is my first Suzuki so I don't want to furk it up.
 
I had absolutely no experience whatsoever when I first started messing with the beastie. My good friend is a fully qualified bike mechanic so the need wasn't there. I bought her new year's eve 1999 and rode her stock for a couple of years then decided, as you do, to chop her up.

15 years later, a whole lot wiser she is as she (hopefully) appears in my signature. This forum is worth it's collective weight in GS spare parts. Whatever issue you're having, someone somewhere has had the same issue and someone else has told them how to fix it. Numerous times in various ways with some posters.

When things are sorted we'll have to meet up somewhere mid-way (Tamar bridge? my jabs aren't up to date!)
 
Chop, yeah the GS has a big ol' ass for a Jap! I was looking at how nice she'd look bobbered. What do you think of Motard (Slowtard)and did ya re-jet for the K&Ns (i'm assuming you got 'em, your bike pic is titchy and i can't blow er up (Tamar bridge, that is) ;)
 
Afternoon. Sorry to take ages to post, usually only check in when it's quiet at work. The exhaust is a Marshall deeptone that came with the bike when I bought it. The filters are generic foam ones fitted when my local bike shop was wiring her as the K&N copies weren't working.
I did have to re-jet, can't remember now what i went up to, I still have the old jets indoors. I have the fuel screw (the one underneath the carbs...never to be touched ever again) out 1/2 turn from lightly seated. the air screws (the ones on the sides) initially out 1 full turn then when she was balanced and warm fettled until she ran at the optimum revs before re-setting the idle using the idle adjusting screw.

Damn, that sounded like I knew what I was doing !
 
Cheers erki52

Just waiting for the shims to appear from Wemoto..... tick follows tock follows tick...... :cool:
 
When these old girls run nicely they're so much fun. Enough grunt to see off most boy racers and a decent enough top end to keep one eye out for the bill. I like that most jobs can be done with the engine in the frame. My old CB900 was a pain, anything other than changing the plugs and it was 'engine out boys'.
 
Your advice was bang on. Got a fire up straight away. Attached a colortune to all cylinders and was in the blue range immediately. Now... I should balance them i guess using the slider adjusting screws? Thanks again Steve
 
If by slider adjustment screws, you mean the screws and lock but under the top cap, those are how you balance the carbs
 
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