1979 GS425 Building more power

[Agemax]

Those are VM24's, which means the slide is 24mm.

Actually, you are wrong. the size of the carb is determined by the ID of the bore where it enters the engine, NOT the slide diameter.

A VM26 and the VM28 has a slide diameter of 31.45mm

[dude99]

Thanks for the clarification.

[Big Rich]

Well I'll be darned...... all the years I've had them and I never measured that. Thanks Agemax.

Dude99, I think the easiest (and relatively cheapest) carb swap for you would be GS500 carbs. There is all kinds of jetting info for intake and exhaust changes on the GSTwins site for them, and they probably just bolt right onto your head.

[dude99]

What years did the GS500 have slide carbs? or did they all?

[Big Rich]

They all have CV carbs with flat slides. The simplest ones were used from 1989-2000. The carbs from 01-02 are kinda odd and hard to find parts for IIRC, and from 04+ they have more jets and emissions equipment mounted.

[dude99]

thanks for the info... I think I'd still like to fit slide carbs though.

[dude99]

I feel I should clarify my last comment. Since we'll be running pods on this build I don't want to run CV carbs as they don't take particularly well to pods.

[Big Rich]

All good man. But K&N makes an air filter specifically for the GS500 carbs. It's called a lunchbox filter and mounts to both carbs at once, and is a popular filter for folks that have a GS500. Just food for thought....

[dude99]

Interesting, and good to know... I'll have to mull this over some more with my buddy who I'm building the bike with.... Having googled gs500 carbs just now I have to say that I prefer the look of slide carbs, less bulky and overall cleaner looking.

Just out of curiosity, would slide carbs give us a snappier throttle response?

[Big Rich]

That I can't answer... it's been a while since I've ridden mechanical slide carbs. And it's been even longer since I've ridden stock CV carbs on any bike.

[dude99]

Fair enough, let me pose a slightly different question then, would slides provide an easier platform for future tuning such as hotter cams etc?

[pete]

I'm happy with my 450 carbs how they are, but I do recall a similar topic around a GS450 quite a long time ago and I believe the recommendation was some VM 29's for the 450 as the best way to go.

[dude99]

Ok, I'll start the hunt for some 29mm slide carbs then. Any thoughts on these? Not 29mm but the price is right (I know, you get what you pay for).

http://www.ebay.ca/itm/Carburetor-Suzuki-DR125-GS125-GS250-GS300-Carb-PZ30-Intake-30mm-Motorcycle-/190806136641?pt=Motorcycles_Parts_Accessories&hash=item2c6cee9741&vxp=mtr

[pete]

From memory he bought new from eBay and I think like that he bought two individual ones from a dirtbike or something... this was quite some time ago for my aging memory!

[84svoUNOH]

Im curious what route did you end up taking dude99? I just bought a 425 and would like to get into some performance mods.