Carb help

[baz]

can anyone help ?ive got a gs1000 which i bought in boxes .Ive got it nearly ready for MOT but need to get it running better,ive noticed the fuel metering screws have been tampered with so can anyone give me some settings for these any info would be great.

[Steve]

It's one thing to adjust it, but it's even better if it's adjusted properly.

Have you gone through the carbs and CLEANED them?
Based on the MOT reference, I'm guessing you are in the UK, so you don't have the same chemicals available that we do, so you will have to see what works over there. Regardless, the carbs need to be spotlessly CLEAN internally and refreshed with new o-rings.

It would help to know what year your bike is. The bikes up through the '79 year had VM carbs. The fuel screws on the bottom should be about 3/4 turn out, and the air screws on the side should be about 1 1/2 turns out, then tweaked for best idle.

The '80 and up bikes had CV-type carbs, which have different adjustments. Your only adjustment on them is the idle mixture adjustment screw, which is on the top of the carb outlet, facing the engine. Bottom out those mixtues screws GENTLY, then back them out three full turns. This will give you a mixture that is rich enough to start and run the bike to warm it up, then slowly turn each one down until the engine loses a little bit of idle speed, and back it up about 1/8 turn.

They might all end up at 2 to 2 1/4 turns out, and don't worry if they are not all the same. What you are setting for is what used to be known in the two-stroke world as "lean, best idle".

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[hampshirehog]

Make sure that the fuel screws aren't missing their tips. Many hamfisted POs made sure that loads are a little shorter than Mr Mikuni intended (and they don't work when they're short...).

[Big T]

Also, what carbs are you talking about?

VM= slide
CV = vacuum

Depending on the year, 1000s have different carbs

[Steve]

VM= slide
CV = vacuum

Could be a bit confusing, there, Big T.

Take a look inside a CV-type carb.

What's that big round thing going through the middle of the carb?

Could it possibly be a ... ... slide???

By the way, the CV is a type of carb, while the VM is a model name.

The model name for the CV-type carbs used on our bikes is BS.
(The siamesed carbs on the '83 and up 550s are BSW.)

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