gs750 carb help!

[horror1972]

Hi,

own a gs750 '78
rebuild the carb with a keyster kit.
tried to adjust the jets with a colortune, couldn't get a maroon blue mixture, found out the air mixture(?)jet made a very small difference but the bottem jet didn't make any differnce at all.
the spark plugs are very black, so there's to much gas.

What does the bottem jet do? what does the side jet do?

what's the stock setting?

anyone can explain why yhe spark plugs are black?

please help!

regards,

marcel
the Netherlands

[tfb]

First make sure you have a clean air filter before attempting to sleuth out jetting problems. A filthy air filter may look clean, but it will make things run richer than you think!

Once you have fixed that, then see how it's running. I'm not saying that you don't have jetting problems, mind; it's just that we must start with the basics.

[horror1972]

ok, found the carb-rebuild pdf on this side, great!
I'm gonna check the carbs agian.
What part of the keyster shouldn't I use?

[horror1972]

ok, and gonna clean the filter, set the pilot jet to 1 turn and the air jet to 1 1/4 turn.
Let you know ..

[Nessism]

ok, and gonna clean the filter, set the pilot jet to 1 turn and the air jet to 1 1/4 turn.
Let you know ..

Sorry but I don't understand when you say you have set the pilot jet to 1 turn? My understanding is that both the main jet and the pilot jet are not adjustable - they should be fully seated into the carb body. The air jet is the only adjustment other than sync and idle speed.

[tfb]

He means the fuel mixture screw, and the air mixture screw respectively, which are found on VM carbies.

[horror1972]

yes, sorry, tfb is right, did mean the pilot air screw and the pilot fuel screw,
Gonna try tomorrow, since it's raining now and my garage is full

Anybody ever tried the keyster kit?
I noticed the jet needle is slightly different ,but looks similair like the one at: http://www.thegsresources.com/files/vm_carb_rebuild.pdf
My original is a bit thicker at the bottem, but anyway, it shouldn't make any difference at idle, low rpm.....

[Nessism]

General thought is to reuse your stock jets unless you have a reason to change. The Keyster kits are somewhat generic and the jets do not always match what was in the carbs origionally.

[horror1972]

Sorry for late reply,
anyway, all tnx for replies.
seems the previous owner tried to rebuild, but forgot to mtighten the choke plungers....
also set the float height to 24 mm and used the original mainjets.
Bike runs fine again.

Thanks

[tfb]

That's good news! Seems to be no end of basic problems that you can inherit with a motorcycle, eh.