Trouble with ignition system...maybe.B

1975 kz400. Bought cheap as a project. I'm not a mechanic by trade, but I can turn a wrench and I'm willing to learn. I started by addressing the carbs. mis-match and who knows what jets and pilots are on this thing so I was able to get the shop manual and TSB's and got all new OEM parts and rebuilt the carbs. Put it back together and I had to turn the pilot screws out 3.5 turns to get it to settle to 1500 rpm. Then...the bike ran great! Started right up, cruises great. But, the spark plugs are always very black and sooty. So that doesnt make sense to me. Why adding more fuel at idle does it run better yet is still running rich? anywyay i thought I'd look at the time. Now I really messed this thing up. Will not run right anymore. 

So started looking at the coil. Primary measures around 5ohms. Secondary is open on most settings and reads 45,000 ohmns on the 200k setting.  Buy a new coil. New coil comes without plug caps so i measure the primary. 14,000 ohms if I remember right. Put the old plug caps on the new coil measures super high again. ok, pull the caps off and measure those and they measure open on 20k setting. have to turn meter to 200k and i get a reading of way high. Oh, didn't realize plug caps had resistors. test the old coil and it reads 13,000 ohms on the secondary without caps. So nothing wrong with the old coil? Plus I notice I'm using br7es plugs. so Buy new NGK 5ohm caps and B8ES plus like the manual states.Now my reading on the secondary is open on the 20k setting and 24,000 on the 200k setting. 

What I'm getting now is bike is running very rough and stutters a lot. I am so lost. How do I know what to start chasing? Should I go back to carbs? Is my ignition setup correct? Timing is a paint. I set it exactly as the manual states and it wont start. I have to turn the point out a little bit while i try to start it and it will start the gap is actually .7 mm, not .3-.4 like the manual states. 

Thank you. Hope to contribute, but for now I'm on the other side of the fence.
Adam

My guess is your spark plugs are very very black now.

You went with a colder plug which will not burn off the soot.
You probably are running very rich but you would have been better off with B6ES to keep your plug temp high enough to burn off the soot. Yet not so high that you pre-ignite.
Not that you can measure it but you want to keep the spark plug insulator between 500°C (932°F) to 800°C (1472°F) in order to keep it clean.

You may have to do plug chops once you get the mixture close.
You also have to figure out which circuit in your carb is causing the fouling.. You may be ok at wide open throttle yet super rich at idle.

something else I just noticed. You used your pilot screws to bring DOWN the idle. You should use the pilot screws to get the HIGHEST idle speed then use your idle speed adjuster to bring the idle down. 

F64 wrote:

something else I just noticed. You used your pilot screws to bring DOWN the idle. You should use the pilot screws to get the HIGHEST idle speed then use your idle speed adjuster to bring the idle down. 

Hmm, I don't understand this. Can you explain?
For example my idle speed adjust (for clairy, it is the flexible cable that changes the throttle minimum stopping point?) is all the way down.

So here is an update: I decided to check the valve clearance and made that adjustment. It now starts and idles nice, but still sputters when it's under load going down the road. I then put in a set of BR7ES plugs that I had already. That had no effect. Still sputtering considerably when hit the road. With the pilot screws set at +3 and idle adjustment at 0(all the way out) it will set and idle fairly smooth (maybe a sputter every now and then). It just really sputter when I go for a ride. Sounds like fuel?
Yes I did the starter fluid trick on the boots and boot plate and no change in RPM.
Thank you

Adam

When you use the pilot screws to lean out the mixture the idle will increase - if it starts dropping off again you have overdone it 
PS: if it idles with the adjuster all the way out there is an air leak or mechanical issue stopping the throttle closing fully 

Wookie58 wrote:

When you use the pilot screws to lean out the mixture the idle will increase - if it starts dropping off again you have overdone it 
PS: if it idles with the adjuster all the way out there is an air leak or mechanical issue stopping the throttle closing fully 
 

Ok, back to the garage. This will take a minute for me to absorb, but thank you!
 

Wookie58 wrote:

When you use the pilot screws to lean out the mixture the idle will increase - if it starts dropping off again you have overdone it 
PS: if it idles with the adjuster all the way out there is an air leak or mechanical issue stopping the throttle closing fully 
 

There continues to be a evidence of an air leak, but I have soaked the boots, the boot plate and the heads with starter fluid multiple times with no change in RPM.

That isn’t always a conclusive test - is there any open vac ports on the carbs that should be plugged?

 

Wookie58 wrote:

That isn’t always a conclusive test - is there any open vac ports on the carbs that should be plugged?
 

Nope. I even plugged the pilot screw holes with my fingers to make sure the orings were sealing. Ugh. Well, its great to have some folks to talk this over with. I've been doing this on my own. I'm not a mechanic, just learning as I go. Thanks again.

Is there slack in your throttle cable? Meaning, you can turn the throttle a little before the carburetors open up? Or is your throttle cable tight?
Does your idle change when you move the handle bars left and right?

Are your caburetor throttle plates closing completely at idle?

F64 wrote:

Is there slack in your throttle cable? Meaning, you can turn the throttle a little before the carburetors open up? Or is your throttle cable tight?
Does your idle change when you move the handle bars left and right?

Are your caburetor throttle plates closing completely at idle?
 

Is there slack in your throttle cable?    yes
Meaning, you can turn the throttle a little before the carburetors open up? yes, its loose. I can see slack in the cable between the carbs.
Does your idle change when you move the handle bars left and right? no

Could the choke circuit be leaking air somehow?