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Motorcycle Repair/79 Suzuki gs750 L


QUESTION: I have a 79 Suzuki gs750 L it has a fuel screw on bottom of carbs and an air screw on sid of carbs what do I need to set them to to get my bike to run and ride properly

ANSWER: Hello Donald,

It would be better if you told me exactly what the problem is...
For example, if the bike hasn't been ridden for a long time, no external adjustment will
solve any problem, without carburettor cleaning.

Anyway, the bottom screw is just a drain plug and doesn't affect engine performance.
(If you mean a single screw though and not one on each carb, that would be the idle screw).

As for the air screw, there is no standard setting. Proceed as follows...
Turn clockwise all the way, until fully seated, but do not tighten it.
Turn counter-clockwise four full turns. Start turning clockwise again, by quarters of a turn,
with pauses, until you get the best idle.

Do this, one carburettor at a time and then start over from the first one, setting the idle
each time you finish one.
If you get the smoothest idle with less than one turn, or, more than three, then for sure you have to take the carburettors apart for cleaning.

Bear in mind that the above procedure is hard even for pros, without proper equipment.
Good luck and get back any time if you need more assistance.

Best Regards,

---------- FOLLOW-UP ----------

QUESTION: I have a Mukuni carb set of 4 thats on my bike it has an air screw on side of carbs and a fuel piolet screw on bottom at back of carbs it ran fine till I cleaned all ports and enjectors and the screws need to be readjusted in order for it to run what should i set them at


Hello Donald,

I have never seen or serviced Mikuni carburettor with both fuel AND air screw, except some
rare racing ones.

Fuel mixture screw on Mikunis is placed either on top or bottom, but at front (towards engine) side.
Air screw on the other hand, is placed at back (towards air-filter) side.
But as I mentioned before, no OEM Mikuni has both.
Pictures of yours, with close-ups of screws in question, would be enlightening.

Let me mention at this point, that, despite that in my profile I state "post-1980" models,
I will do my best to help you out, if you help me identify the carburettor type that's on your bike.
I attach pictures of the Mikunis (BS22SS) that's supposed to be fitted on it.

Best Regards,

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Lazaros Ampatzidis


I can help you on EVERY issue involving POST-1980 Japanese Motorcycles plus KTM and Husaberg. My field of expertise includes Engine, Transmission, Fuel system (carburation & EFI),Electrics and Electronics. Maintenance, repair and tuning. Road and off-road suspension tuning. Please don't ask me about non-Japanese Motorcycle, especially American built on which I have low to zero experience.


I'm a rider and hobbyist since childhood. 25 years motorcycle workshop mechanic.15 years motorcycle racing mechanic. In order of experience high to low:Kawasaki,Suzuki,Honda,Yamaha,KTM,Husaberg.

Hellenic (Greek) Technical School.Internal Combustion Engines Engineer. Automotive Electronics.

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