air screws on cv carbs.....

[Seana23]

Hi all. Just rebuilding my carbs and wonder if the tiny o-ring that goes with the air screw sits under the screw or goes a little way up the screw?
Thanx all.
X

[hampshirehog]

Take a look at:

http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

It should be (from the bottom) O ring, washer, spring, screw - with the washer in place you'll see that they o ring can't be part way up the screw (other than the pointy bit at the bottom). And the 'air screw' is more correctly termed the mixture screw on CV carbs. If thos little o rings have got hard or cracked it's time for new ones.

[Steve]

Nice to see you posting again Seana.

Terminology: You don't have "air screws" on your carbs, they are "idle mixture adjustment screws".
They are called that because they actually control how much of a pre-set mixture is allowed to get to the cylinders, not just controlling air.

Now to answer your question: When assembling the mixture screw, put the spring on the screw, then the little flat washer, then the o-ring. The o-ring will slide up the shaft of the screw just a bit and will hold the other parts in place while you put the screw into the carb. As with all the other o-rings you are probably replacing, put a drop or two of oil on it to let it slide into place when you assemble it.

Turn the screw in until it LIGHTLY seats. (I will actually back it out a bit and re-seat it several times, just to make sure that everything is seated well.) Then back the screws out three full turns. This will richen the mixture just a bit more than necessary, but will make the bike easier to start so you can warm it up and tune it properly.

Tuning the mixture screws involves listening for changes in idle speed. You want the leanest possible mixture that does not cause the speed to drop. That might be with the screws around 2 to 2 1/2 turns, but it will start just fine with the initial setting at 3. Think of it as a mild "choke" to get everything going.

.

[Katarat]

A little anti-sieze on them too If I might suggest, also on the pilot jets. Saves a ton of problems later on

[Seana23]

Thank you all.
I thought they looked at home, part way up the shaft ov the mixture screw (thanx for correcting the on that one)
Lovely to see you all again.

Got the bike mot'd now so its roadworthy but i had a wee problem with some crappy tank liner disolving into the fuel and gumming the carbs and inlets up!!! Do'h!
Anyway, nearly done the carbs (for the 10th time!) now. Also i got them ultrasonicly cleaned so i think we may be good to go...
Fingers crossed.

Thanx for all ya help.
Xxx