1975 KZ900 Advance curve information

blue75kz900 wrote:

...tried turning out to 1 1/2 turns but idle ran too fast. The bike is also idling too fast right now. After its warms it runs 1000-1500....

Assuming no racing idle due to air leaks (from such things as cracks in old worn out carb holders, loose clamps on carb holders, hard dry vacuum plugs, etc.), should tune pilot circuit by sequentially adjusting air screws to attain highest idle rpm, then use idle thumb screw to reduce rpm back to idle speed, then repeat, until have best idle possible that can't be improved by further pilot screw adjustments.

Good Fortune!

Thanks for the info. I'll try that.

Not sure where you got the info but the 2.2 ohm is the recommended coils for the Dyna 2000 CDI ignition. This was a retail boxed kit from them. DDK2-1C, the C designates coils included.

I thought that more air through the pilot passage would also take in more gas. At least that's what the pictorial suggested.

blue75kz900 wrote:

I thought that more air through the pilot passage would also take in more gas. At least that's what the pictorial suggested.

Perhaps looking at a carb having pilot MIXTURE screw as opposed to pilot AIR screw.

AIR screw is typically side-located (more toward air intake end of carb).

MIXTURE screw is typically bottom-located (closer to engine side of carb). Turn in for leaner pilot mixture, and turn out for richer pilot mixture (which is opposite of air screw type carb).

Good Fortune!

[Click on image to enlarge view.]

blue75kz900 wrote:

Not sure where you got the info but the 2.2 ohm is the recommended coils for the Dyna 2000 CDI ignition. This was a retail boxed kit from them. DDK2-1C, the C designates coils included.

If that is the way it came from Dyna than I guess the 2.2 Ohm coils are fine. I just went on the WWW and found the info. Never mind than. :blush:

Thanks Patton for all your information so far.
So I only have an air screw adjustment. The pilot jet that's in it now is the 17.5. So I should stay with that and adjust the screw in or switch to the 20 and adjust from there?

What air filtration and muffler/baffles are fitted?

Pods and open meg might do better with larger pilot.

I would try sync and fine tune with existing 17.5 pilots to achieve best possible idle. Wanting a slow steady idle rpm with strong pull-away. Could then add a little choke at normal operating temp to see whether it helps or hurts pull-away performance.

Meanwhile, what are now existing compression test figures?

Would also assure visible fat blue spark in darkened garage.

The ultra long warm-up required is still indicating a too lean pilot circuit for whatever reason.

Perhaps a current summary of remaining issues would be helpful to diagnosis.

Good Fortune!

Compression after 100 miles. 
1. 120 
2. 115
3. 115
4. 105
Now has 184 miles on engine cleanup.
Because of bad ignition for first 150 miles have a lot of carbon build up which I bead to get rid of some how.
Air breathers are new individual pods.
Single exhaust is Yoshimura.
In the next day or two I will try your suggestions.
I will adjust the needles one clip up to the number 3 location and turn the air screws in to 1 turn out from seat.
Any good suggestions on carbon removal? This really bugs me since I spent so much time taking it apart and cleaning it out. Too bad I didn't have the new ignition in right after the rebuild.
The bike didn't rum too bad today but not great because it was raining a bit on my way to work.
Thanks.

Hi Patton, hope your day has gone well.
I had a chance to make an adjustment tonight.
I set the needle clip in slot 2 from 4
Turn the air screws in so they are now 3/4 of a turn up from the bottom instead of the 1 1/4 turn as in my and your information.
I started it up briefly and it ran.
Will find out on the morning on my way to work how it works.
Thanks.

Well the ride into work wasn't great.
I did get more power at the bottom end with the air 3/4 of the way out. But I think I went too far with the needle in the number 2 slot. Mid-range throttle sucks for most of the way to work. Started runing a little better as the bike warms up more. 10 minute warm up and ran poorly for first 10 minutes, the last 10 minutes wasn't that bad. On the way home I turned in the screws another 1/8 turn. Didn't get a chance to work on it tonight, had to fix my helmet. I will move the needle to the number 3 slot and turn the screw back to the 3/4 mark.
More fun later.