Z650 slides on a GS 850..?

[Seana23]

Hi all,
a friend is breaking a Z650B1 that has Slide carbs and i was hoping that they might fit my GS850...
been looking for replacements for the CV carbs fitted to my 850...
Then these came along.
Does anyone know if they will fit?
Thanx all.
Xxxx

[Steve]

Seana, if you choose to downgrade your carbs back to the slide types, you will also have to change the intake boots and airbox boots (if you still have an airbox). Not sure if the head is different, but the '79 850 had slide carbs, so it would have the smaller boots necessary for the smaller carbs. Check the part numbers for the head and airbox on the '79 and '80 850s to see if they are the same. If they are, you will only have to change the boots.

As to whether the carbs themselves will fit ...

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[Seana23]

Hi again...
Info update...
The Z carbs are VM 24SS's..
I realise the intake boots will need modifying...
I have pods so airbox is irrelevant..
The carb lateral spacings may be different too i spose...
Im just looking for carbs that don't need such fine tuning and rely on Venturi effects and vacumes to get the needle to move properly...
Thought Slides may be an answer, then yhe next day my friend said he has his ones from the Z going spare... I thought this was meant to be...!
Thanx Steve any other input greatfully received.
Xxxx

[Big T]

Seana,

I believe the lateral spacing on the VM 24s will be too tight

You should see if someone has a set of VM26s laying around that you could get

Other alternatives are Z1 28mm and 29mm smoothbores, each are more costly

[Steve]

Im just looking for carbs that don't need such fine tuning and rely on Venturi effects and vacumes to get the needle to move properly...

Actually, for street use, the stock carbs on your bike are about the best.

With the "slide" carbs that you were trying to put on, you could whack the throttle open at low speed, which would too much for the engine speed. Response would suffer, because there would be no air flowing across the jets to feed the engine.

Having the CV-type carbs (your stock ones) in there, you can open the throttle butterflies, but the vacuum-operated slide (basically a variable venturi) would keep the air velocity rather constant over the jets, ensuring good response. It is that (relatively) constant velocity that gives the carbs their name: Constant Velocity. When there is enough air moving under the slide to generate a bit of vacuum (it's venturi vacuum, not engine vacuum), the slides are lifted to allow even more air through. When the slides are lifted, the needles are also lifted, giving proper carburetion for the actual air speed through the carbs, not just the throttle opening.

For racing use, the slides going up and down in response to vacuum levels is just too slow, so slide carbs are better for racing, but the "vacuum" carbs are better for street.

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[SqDancerLynn1]

For the larger intake port you can use the 33mm smooth bores. They are more of a race carb...
Don't discount your BS carbs !!!! if cleaned and tuned properly they work great

[koolaid_kid]

Actually, for street use, the stock carbs on your bike are about the best.

With the "slide" carbs that you were trying to put on, you could whack the throttle open at low speed, which would too much for the engine speed. Response would suffer, because there would be no air flowing across the jets to feed the engine.

Having the CV-type carbs (your stock ones) in there, you can open the throttle butterflies, but the vacuum-operated slide (basically a variable venturi) would keep the air velocity rather constant over the jets, ensuring good response. It is that (relatively) constant velocity that gives the carbs their name: Constant Velocity. When there is enough air moving under the slide to generate a bit of vacuum (it's venturi vacuum, not engine vacuum), the slides are lifted to allow even more air through. When the slides are lifted, the needles are also lifted, giving proper carburetion for the actual air speed through the carbs, not just the throttle opening.

For racing use, the slides going up and down in response to vacuum levels is just too slow, so slide carbs are better for racing, but the "vacuum" carbs are better for street.

.

This is the exact reason I sold my 1978 GS750E after less than a year of ownership. I hated it, and still do. This was in 1979, so there was no alternate GS available. I went back to an RD350, which I could whack the throttle open and point to the stars.

[TheCafeKid]

You may want to double check that info on those KZ650 carbs. I have a set as well and they're VM26ss. Now they may have been different on that side of the pond I dunno.

If you WANT a set of VM26s, I have a set I'd be willing to sell. If you just need parts for your CVs I have that as well. Including a set of good slides/diaphragms.

Honestly, though, unless your bike used the mech slide carbs originally, you'll have to spend a bit of money to use those in new boots and possible mods to said boots to get them to fit to end up using a carb that's really no better than what you have unless you're planning on pods and a pipe. And that's simply because the VMs are easier to re-jet for pods as you can do it by hand instead of having to source a jet kit.

[Steve]

You may want to double check that info on those KZ650 carbs. I have a set as well and they're VM26ss. Now they may have been different on that side of the pond I dunno.

I checked.

From Wikipedia:

1981/82 Z650-F3
There was one major change for 1981/82 F3 model, 32mm Mikuni CV carbs were fitted. These larger carbs allowed the redline to be lifted from 9,000 to 9,500 rpm. The larger 32 mm carbs also needed the accelerator cable and air box assembly from the Z750E/L models. The front fender was now also painted to match the rest of the bodywork. The drive chain was the bigger 630 chain as fitted to the Z650 F2 onwards & 13/33 front & rear sprockets . The indicators were changed from round to rectangular. Approximately 1,900 units were produced worldwide for this model.

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[TheCafeKid]

I checked.

From Wikipedia:


.

Yes you did...but she said hers were from a 650B1. Which would make it a 76/77 model. Or somewhere in there...those had VM carbs. I couldn't find a bore on the carbs listed on any of the spec sheets, but I do know the set I had came off of a KZ650 (whether they were original equipment or not I can't say) and that not only were they 26s, they also have the same port spacing as a early 2V GS head. Jet sizes were not the same obviously, and the cut-away on the slide was marked with a different marking but I couldn't physically see a difference in the cutaway compared side by side with a slide from a set of 26s from a GS.

I also have a set of 26s off of another Kaw (were fitted to a KZ1000Ltd but weren't original equipment) that are different in that they have no pilot air screw. The spot where they would go is blanked off. The guy had told me, before I saw them with my own two eyes that they were 29 smoothbores, and had traded them to me for work on his bike. I was slightly upset that I'd done quite a bit of work for what amounted to a $100 set of carbs on a good day, but those are the breaks