TOPIC:

For some time now I've been starting my engine with the chock up, to fully chock at cold start. That is fine, but when I release the chock it stops firing on all four cylinders. It will jump around and spit before it actually runs good on all four. The only way to get around this is to colaps the filters to manually chock the carbs after that it runs great.
The carbs were cleaned, new jets 15 pilots, 102 mains, synced/ balanced, air screws at 1.5 turns.
The bike (when warm) runs great no missing or sputtering. The ONLY problem I have is having it run on all four when switching from full chock to half or no choke. This will be a problem soon because I have plans on k=n filters in the future, and those are not collapsable to chock the carb.
How can I fix the problem.

Most of these old bikes are fairly cold blooded and can take several minutes to warm up properly. I usually have full choke on for a few minutes and then gradually reduce it to half while I put on my jacket, helmet and gloves. I only get the choke fuly off as I'm riding up the street. The bike may be running for up to five minutes with some degree of choke. I just wonder if you are leaving the choke on long enough.
These days we are all spoiled with computer controlled fuel injected cars with automatic chokes where you just jump in turn the key and drive.

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Woodstock ON Canada
1980 kz750E1, 4->1, K&N pods

I would keep the chokeonlonger, but man if I keep it on for more than 10 seconds it fills the drive with black smoke. I place chock 3/4 as soon as it starts. Then chock the carbs out by pushing on the pod filters one at a time. Then as soon as I do that it runs great. No need to keep chock on longer than 20 seconds. Thats what leads me to believe that there has to be something wrong with the fuel switching from choke to no-choke.
I dont mind tinkering every time to start the bike. Its just that I would like to go with k+n filters. I believe that they look better then pods. Though you cant colaps them to choke the carb manually. This means that cold start will be a mother of reving and choking and spitting:(

Has anyone experienced this?

Okay, this is a long shot, but are you sure your timing is right on?

other than that, the extra smoke makes me think it's running rich, but the need to collaps the filters for extra choke makes me think it's too lean...

Check your manifold boots. If they are loose and letting in extra air, it might be throwing off your results.

That's all I can think of.

sounds like you are having a lean condition at idle (off choke).I am running 17.5 pilots on my 77 650 b1 and as soon as it fires on full choke I have to go to to 1/2 choke for a few minutes and then go to almost no choke then clean it out by snapping the throttle a few times then the lil girl is good to go.

Good Luck

KB02 wrote:

Okay, this is a long shot, but are you sure your timing is right on?

other than that, the extra smoke makes me think it's running rich, but the need to collaps the filters for extra choke makes me think it's too lean...

Check your manifold boots. If they are loose and letting in extra air, it might be throwing off your results.

That's all I can think of.

Dont realy know for sure if the timing is spot on.
I only have to colaps the filters for a second with no choke to get them to fire. After that its gas and go. Its that transition part of the bike high idling on all four with choke to no choke and spitting, untill I collaps the filters for a second.
Hmmmm gave me an idea about the timing though. I did have my head shaved about.030. Do ya think it is out of cam timing?
The boots are new with no leaks that i'm for sure of.

Snakebyte wrote:
Hmmmm gave me an idea about the timing though. I did have my head shaved about.030. Do ya think it is out of cam timing?
The boots are new with no leaks that i'm for sure of.[/quote]

With that shaving of the head, it could have slackened the timing chain causing it to pull the cams out of perfect timing. Once again, it's a long shot, but heck, if you;re right there working on it, it's worth a check. The worst that will happen would be a readjusted timing chain.

On my GPz750, I have shaved the heads. The sites I have read recommend slotting the cams so they can be degreed. Look at members.tripod.com/gpz_rider/technical/FAQ2000.htm and read through the article.
Please note, my engine is still in work, and we will be slotting the cams this weekend. I will know more after we do the work and get the beastie running.
Best of luck.

I run mine at full choke for about 2 miles before I turn it off otherwise the bike will not run. It runs great while warm like yours. That is normal for these older bikes they wre shipped running VERY lean to pass emmissions.
I have a 78 KZ650C with 710 big bore kit, K&N pod filters, GPZ cams and a 4 into 1 pipe. The jetting is 118 mains, 17.5 pilots, 1 2/2 turns out on the idle mixture screws and the needles are two from the top.
Just get used to riding it with the choke on for a few miles.

have you checked your float levels using the "wet" method.
It kind of sounds like maybe one or two of your carbs arn't set quit right.
Manually choking the carbs is forcing them to draw fuel from the float bowl through the idle jet.
Just a thought.