Hesitation/Surging/Carb Tuning HELP!

[gatorgrizz27]

Alright, I have a 2001 M600, I replaced the needle jets, set the float heights at 14mm, and set the pilot screws at 2.75 turns out.  I synced the carbs as per my vacuum gauge, but I am not certain they are correct, as when cold it idles at around 800 rpm, and when hot idles at just over 1000.  Also, it does not seem to have as snappy of throttle response as it did when I synced the carbs before.  The bottom end power is much smoother than it was before, and it no longer stumbles when at partial throttle from 4-6k rpm.  When accelerating smoothly, it seems to be fine.  If the throttle is whacked open, it picks up for a split second then surges somewhat, slowing down for a bit, then catches and runs fine.  I assume this means the float heights need to be set to around 12mm and it is running out of fuel when you open the throttle too quickly? 

The other problem is only evident when you are cruising above 60mph and above 6k rpm as well.  The bike surges or stumbles somewhat, there is no popping or noises, but it feels like you are running into a buffeting headwind or tapping the brakes intermittently.  If you are below 6k rpms, or below 60mph, it works perfectly and runs fine.  Could this be a sync issue or a pilot screw problem?  Would it be possible that I need to turn the pilot screws further out?  Thanks for any tips you have.

*Edit*  This bike also came with a K&N drop in filter, the airbox lid is stock, and I shortened/cored out the exhaust, but I don't think I need to rejet it?  I also removed the plastic pods that the carb vent hoses were in, and just tied them up next to the frame.  I found a few posts saying they need to be in clean air, so I will extend them up underneath the tank.  Could that along with float heights be the two problems, or is it likely something more?

[Howie]

Your idle needs to be higher, 11-1300 RPM.  14 mm is correct for the floats.  By pilot screws I assume you mean the idle mixture screws?  If so, they only affect closed throttle and just off closed throttle.  If the air box is stock your jetting should be fine though stage 1 jetting wouldn't hurt.  It is possible that the vent hoses could be your problem.  You should move them out of the airsteam anyway. 

[bigiain]

The other problem is only evident when you are cruising above 60mph and above 6k rpm as well.  The bike surges or stumbles somewhat, there is no popping or noises, but it feels like you are running into a buffeting headwind or tapping the brakes intermittently.  If you are below 6k rpms, or below 60mph, it works perfectly and runs fine.  Could this be a sync issue or a pilot screw problem?  Would it be possible that I need to turn the pilot screws further out?

I don't think that's pilot, I think you're running mainly on the needle jets there. I'd suspect it's running rich from your description, first thing I'd try would be moving the needle clips up a notch or two (depending I guess on where they are already, if they in the top or second top position now I'd probably drop a main jet size and start tuning again).

+1 on Howie's suggestion to nudge the idle up a little as well - they _can_ idle down below 1000rpm, but they run quite a bit nicer if you're up over 1100.

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