turning air screw

[goggleboy]

You can't adjust carburetors that are badly out of synch. You can try, but it ain't a gonna happen. I would be willing to bet the vacuum levels on your carbs are all over the scale. Do a vacuum synch. That is step #1 in carb adjustment and tuning.
Until the carbs are all drawing the same volume of air, you can't adjust crap.

Earl

you know what, that's what I'm thinking. That would cause lingering high idle... I did a bench sync, and made sure the slides were all 1mm past the opening... but that doesn't guarantee they are all pulling the same vacuum right?

[Octain]

If you havnt recently, might not hurt to try a new set of plugs.

[goggleboy]

If you havnt recently, might not hurt to try a new set of plugs.

..I guess.... they are not that old. No more than 500 miles on them.
New dyna S ignition, green coils, and taylor wires. I have insane spark, like I said, I need to hook up the timing light agian to make sure that spark is firing at the right time. I did once already and marked the rotor with white paint. As I revved the white marks grew farther part, normal. My GS just starts so good, no smoke, new parts, fresh cleaning... it makes me sick!

[earlfor]

you know what, that's what I'm thinking. That would cause lingering high idle... I did a bench sync, and made sure the slides were all 1mm past the opening... but that doesn't guarantee they are all pulling the same vacuum right?

I can guarantee you the carbs are NOT puliing the same vacuum. The point of a bench synch is to get it to run long enough to do an actual synch. A bench synch is nothing more than your best guess at making an adjustment on something you can't see or hear.

Earl

[goggleboy]

I can guarantee you the carbs are NOT puliing the same vacuum. The point of a bench synch is to get it to run long enough to do an actual synch. A bench synch is nothing more than your best guess at making an adjustment on something you can't see or hear.

Earl

so your suggesting I get it synced with a sync tool. I want to buy one, which one would you suggest? this is the only thing I could think could be wrong.... besides the #2 carb spitting fuel sometimes from the overflow nipple. I don't run hoses from the nipples, would this create any problem?

[OldVet66]

Some carbs don't show much difference in the air adjust. Once you get it properly synchronized, and in the ball park some of the carbs might not show more than a half or whole needle width in adjustment on the tach, but can make a huge difference in idle, power engaging the clutch and low speed manners (25 to 30MPH without any surging). You might want to invest in tubing for your overflows. Floats will stick and the results on a hot motor and exhaust might be less than pleasing. I believe the Morgan is the overall best manometer.

[KEITH KRAUSE]

Did you inherit this problem or did it run fine before your work? A 750 that won't rev past 6K or go beyond 80 mph?
Before blaming the carbs...
Do you have good compression at all cylinders?
Is the gearing (front/rear sprockets) stock or close to?
Are the throttle slides opening all the way (by actually operating the throttle housing)?
Since full advance timing kicks in about 2K and you saw the timing move I doubt the timing is causing a problem at 6K.
Any chance you did something to lessen air flow when you "weather sealed" the airbox? Are the factory installed airbox holes clear?
Are you sure there are no leaking intake issues?
Is your air filter a dry filter or does it require oiling?
Are the floatbowl vent lines and vacuum line connected correctly and not kinked and open to breathe?
Is the petcock flowing well? If you test for top speed with the petcock in PRIME, any change?
Any fuel filter being used?
If all above are OK then look at the carbs. Are you POSITIVE the carbs are the correct ones (VM26MM)? Is the jetting stock? What size mains? Do you know what position the jet needle e-clips are in?

[KEITH KRAUSE]

And yes, the vacuum synch is important. However, any decent bench synch will still allow the bike to reach near top speed and much higher rev's than 6K. With generally poor/uneven vacuum the bike will not run as smooth or perform its best but if the slides were so uneven that it caused a top speed/rpm issue as you describe the bike wouldn't even start.
Another question I forgot to ask in my previous post...will the bike rev beyond 6K in neutral?