I recently replaced plugs, shimmed the needles and replaced the carb rubbers. I ended up with a terrible misfire / popping. I checked the carbs for air leaks and found one using carb cleaner on the rubbers. Took the carbs off, refitted and checked again. No leaks but the misfire persisted. Can raising the needles on a 30 upset the fueling that much, and can it be leaned out by adjusting the A/F screws outward? They're currently set at 2.25.

The air screws only control the idling of the bike, the needs control the fuelling of the main jets.

Where is it popping / running badly, at idle or when your riding the bike?

it's running badly / missing right through the rev range

Have you not taken the extra washers back out and tried it?

emto wrote: Can raising the needles on a 30 upset the fueling that much

Basically, no. It sounds like you have another air leak.

Thanks lads, so I can leave in the shims in that case and look at my technique of fitting the carbs. I usually try to fit the fronts first and lock them up before trying to fit the rears.
Would leaving the fronts loose in the rubbers before fitting the rears and then locking up all four be a better option, or does it make any difference?

Leave all the rubbers loose untill the carbs are sitting in place and correctly seated and then tighten the clamps.
Maybe try this and if it still runs like shit try reversing what you have done (Lower the needles back).

emto wrote: I usually try to fit the fronts first and lock them up before trying to fit the rears.
Would leaving the fronts loose in the rubbers before fitting the rears and then locking up all four be a better option, or does it make any difference?

Definately get them all seated properly before doing any clamps up. I use a torch to check that all the carbs are the same distance from each rubber before tightening them up.

The way you've been doing it will be loosening the front ones out when you pop the rear carbs in. I think this will be causing your problem, try it the other way and see how you go.

Stickshift wrote:

emto wrote: Can raising the needles on a 30 upset the fueling that much

Basically, no. It sounds like you have another air leak.

Agreed. Extra air is leaning your mixture out.

Spray the rubbers with carb cleaner while its running, you'll hear a change in rpm when you find the leaky one(s).