VM29SS - 1976 GS750 - Good/Bad?

[Z32650S]

So I scored a set of VM29SS flat slide carbs off a 1985-86 GSXR750 (non-US model).

My GS750B is a backyard find and is in the very early stages of teardown in view of a winter cafe build. I took the OEM VM26 off for cleaning/refurbishing and am considering my options. Keep the VM26 on the bike or as spares. I'm drawn to use the more performance oriented VM29SS.

The bike has a 4-1 exhaust (possibly a Kerker?), and had pod filters fitted when I got her. The pods are done so I'm likely trashing those in view of fitting velocity stacks for either model carb.

I'm wondering if the VM29SS are just overkill on the GS750. I hear they are great street carbs, but I'm just not sure if they are a reasonable fit on a 750 as opposed to a 850 or 1000cc bike. I tried searching and found a few folks with VM29 smoothbores but never the VM29SS.

Any carb gurus have thoughts to share?

By the way this site is great!! I've been reading tons of useful tips and tricks. Thanks!

 

[Nessism]

What are VM29SS's? How about posting some photos? Many of use are familiar with the VM29's, but not the VM29SS's.

 

[49er]

What are VM29SS's? How about posting some photos? Many of use are familiar with the VM29's, but not the VM29SS's.

Ed, both our VM26 and VM29 Smoothbores are SS model carbs. It just denotes they have spigot mounts for both their inlets and outlets.

Those VM29 flat slides are fairly rare. IMMSMC, they only appeared on the '85 GSXR750's down here.

 

[tkent02]

I'm wondering if the VM29SS are just overkill on the GS750. I hear they are great street carbs, but I'm just not sure if they are a reasonable fit on a 750 as opposed to a 850 or 1000cc bike. I tried searching and found a few folks with VM29 smoothbores but never the VM29SS.

Best would be to use a GS 1000 engine in your 750, then use the 29s.

It's lighter and smaller than the 750 engine, bolts right in, (you need to make some longer motor mounts, easy stuff) and has much more torque and power.
The 29s should work great with it.

 

[Z32650S]

Thanks for the replies.

I'd love to swap a 1000cc engine in as suggested, but alas, I likely won't be doing that anytime soon.

I was hoping I could make these special carbs work on the 750 since they have the 77-93-77 carb spacing and bolt right up. The accelerator pumps are also a bonus as they make the carbs less snatchy when coming off idle. They look similar to the Mikuni TM33 but are indeed diferrent.

I'll try some baseline jetting suggestions for sea level. I'm thinking around 120 main, 17.5 pilot with velocity stacks and 4-1 would be a decent start. Heck, I'm just shooting numbers. I'd likely follow in the footsteps of other setups with VM29 smoothbores. Not sure they would be the same, but worth a try. Jetting suggestions, comments or other considerations are welcome!

As requested, here are some pics of the VM29SS:

 

[GregT]

Here in NZ both the GSXR 750 H and the I came with those carbs plus there were a shedload of Jap home market bikes imported with them. I've used them a lot on speedway TQ motors.

Very tuneable. Your initial jetting picks will be pretty close.
Needles - there are actually a couple of different needles available. Different markets used different needles. The Jap home market ones have a richer needle but used a leaner pilot jet. I've got the numbers written down here but would need to look them up - it's been a while....

They will work well on the 750 - the 29mm restriction in the entry side raises air speed over the jets and ensures very good response.
It is also possible to turn them into replicas of the GSXR racekit carbs by boring them to 33mm straight thru....

 

[KamakaziX]

Hi there! I'm shamelessly resurrecting this. I figured it was better than starting a new thread.

Anyways, I bought some SS's for my '79 GS750. I've heard oversized carb inlet boots and head porting is needed. Is there any validity to that? Or can I get away with jetting and bigger carb boots? Any help would be greatly appreciated.