Air mixture screw on VM carb #2

[rthor]

On carbs number 1, 3 and 4 I get a good reaction when I set the air mixture screws. For instance, when I dial them right down, the engine will bog down and virtually stall. But with carb #2, there is hardly any noticable change in idle when I bottom out the air mix.
The spark plug is good in #2 (as is the spark). Any ideas???

[Nessism]

Don't worry about the lack of response, set the screw the same as the other carbs and you should be fine.

[Steve]

There is a possiblity that the tip is broken off, but if it is running OK, don't worry about it.

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[Nessism]

There is a possiblity that the tip is broken off, but if it is running OK, don't worry about it.

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The broken tip problem on VM carbs is the fuel screw. If it's broken off there will be no fuel flow since the tip plugs the orifice.

[hampshirehog]

Could be that your pilot circuit on no 2 is blocked - you can still get a GS550 to tickover (reasonably) well if it is blocked. Why on a 550? Layout of the 'double' pilot jet circuit? I don't think so but it is peculiar to the 550 and there's 'owt else different with the other bikes. Works on some 550s but not others even with a good synch.

2 easy ways to test: if you've got a Colortune pop the glass spark plug in no.2 and see if it's firing consistently on tickover. Or start the bike from cold on tickover only, if it will, and put your hand on the exhaust - the ouch test - to see if it's as warm as the others.

[skidMarkNZ]

I would say that carbs grubby, take them too and strip them all right down and give the ma complete clean out before you even consider tuning.