revs really high when starting cold

After reading the entire thread, I think you should check for an intake leak again.
What happened to me:
My 750 would idle at about 4000rpms when warmed up. I looked for cracks in the vacuum system, carb holders and such and found none. It wasn't until I sprayed starting fluid (not recommended, but at the point I was at I didn't care if the bike burned to the ground). Sure enough, there was a vacuum leak. I pulled the carbs and there were no cracks in the boots. I decided to remove them for closer inspection and 3 of the 4 were loose with one of the boots I could turn the screws without a screw driver! I cleaned up the surfaces, tightened the screws using loctite, balanced the carbs. No issues since.
I hope you find the cause of the problem.
Joe

Saki Jockey wrote:

Best of luck, welcome to the forum. Ps. Don't be shy, add your city and state and your bike model to your signature.<br><br>Post edited by: Saki Jockey, at: 2008/03/05 21:59

I second all four points made here.

I repeat, check the throttle cable for visible slack. And you mention that the problem starts at lights? When you are sitting there at a normal idle, does the idle jump up to 6K rpm? This symptom sounds like choke plunger pads are NOT seating. This allows air to leak across all four enrichener circuits and the rpms will jump dramatically. It is easily checked... next time it happens, jiggle the choke lever. If it is a seating issue, it will come right down.

Could the gasket be my issue? I just took a photo of the left carb so I could match up the collar that you can see broken in the photo to the Babbitts order form, and I noticed (can't believe I didn't before) that the gasket seems to be sticking out. If that were the case wouldn't the rpm's be through the roof all the time instead of just occasionally? Thanks.

Post edited by: Boll Weevil, at: 2008/03/08 18:14

whoops

The gasket has no effect on rpms... the gasket noted has no effect on the operation of the carburetor. It is there to keep stuff from getting in the carb body I guess. I have already told you the most likely reasons the revving occurs.

I figured the gasket didn't have anything to do with the air flow, but wanted to cover all bases.

I finally got inside the throttle cables, took them entirely out and gave them a good cleaning and lube with some thin chain oil. A quick 20 min ride on the bike went over smooth without any of the rpm's shooting up as there was in the past. Tomorrow I'll put it through the rigors of my lengthy commute from Brooklyn up to Harlem and a bunch of stops between, hopefully she keeps going as smooth as I'm hoping.

I also gapped the points and it seems to have made a difference in the power flow on the low end. Before the bike would sometimes lose power on the low end, and occasionally just lose power and die altogether. I haven;t been able to get my hands on a strobe to time the ignition. Money is tight and I'm thinking of putting my money toward a Dyna electronic ignition in the future. Eventually I'd like to check over the valve clearance, but feel a sidewalk out in the open isn't the best place to pop into the thing.

Thanks to all for bearing with me and some of my banal questions, and my apologies if they've come to the point of being annoying. It's been some eight years since I owned a bike, and then I always had my dad to assist and a nice, private garage to work in. Without this forum I think I'd be lost, sitting on the sidewalk in Brooklyn, wrench in my greasy hand and a puzzled look on my face. Its proven to me that the camaraderie between cyclists can transcend pretty much all boundaries to the point I can get help from total strangers potentially thousands of miles away. Go KZRider!

-Ben

Ben, The Dyna S is really a money-saver over the long run but you will need a timing light to set the new ignition up when you get it. I would think in your area there is another KZRider member willing to help with that install when you get to it.

Boll Weevil wrote:

Could the interior ignition issues be responsible for the bike sometimes puttering out and losing power, then dying? When this happens it usually starts right back up. Just became a problem riding around the city today running errands. The bike would feel sluggish then die in response to opening throttle....

Might be a fuel delivery problem, such as crud inside the tank collecting around and obstructing the petcock tubes running up inside the tank, or perhaps the screen petcock filter is clogged. Or maybe a clogged in-line fuel filter.

Anyhow, an easy test is by removing a floatbowl drain screw and watching to see if gas keeps freely pouring out. That assures ample fuel transfer from tank into floatbowls. If fuel flow from open drain screw hole is too slow, try opening the gas cap to see if that makes any difference.

If petcock pickup tubes inside tank are clogged, the petcock may be removed from the tank and carefully cleaned, as the screens are delicate. Could also remove tank, dump fuel through cap opening, add a quart or so of clean fresh fuel, slosh it around, and dump it out through the cap opening. This should clear most of any loose crud which had been floating around inside the tank.

Good Luck!

Boll Weevil wrote:

whoops

In this picture, looks like the choke lever
is pulled up into the full on position.
Am presuming the choke lever is raised
only when first cranking up a cold engine
(with throttle left alone in the fully closed
position while operating the starter motor
or kickstarter). And that the choke
lever is pushed back down into its
normal off running position as soon
as possible so as to avoid unnecessarily
racing the engine or flooding the plugs
with excess fuel.

Just thoughts from seeing the pic.