Running rough and now won't start

I tried the tank cap open test and still produces the same issue.. Starts like a gem, idles well, but lags big time when you open the throttle. Gas flows freely from the petcock and into the carb...so, no issue there.

Since things were running well, in terms of the carb settings... and it wasn't my points/condensers, I'm wondering if maybe there is some debris (aka rust) somewhere in the carb, blocking the proper amount of fuel from getting through?..I already pulled and cleaned the carbs but I didn't do a complete tear down.. My mistake!

I'll take LineArtist's suggestion and test my coils as well.

I'll update once I find some time!

If not already done, would assure that heads of screws attaching wires to coils' primary terminals aren't shorting against a coil mounting spacer.

In the following example, the metal spacer has been replaced with a non-conductive (plastic or nylon?) spacer.



Good Fortune!

Two different bikes with sooty plugs and same symptoms. Have you checked the valve adjustments?
Steve

-

Just got finished testing the coils and here's what I got:

primary coil resistance on both coils was 3.8ohms-4ohms as the manual said.
The secondary coil resistance (plug to plug on the same coil): one coil produced about 14k (manual said it should be 23k) and the other produced NOTHING.. At first , I'm thinking that's not possible, there would be SOME sort of reading. Correct me if I did it wrong.. set my multimeter to 200k Ohms and inserted a prong into each of the plug caps.

Does this make sense?

MaxKZ wrote: The secondary coil resistance..... and inserted a prong into each of the plug caps.

Secondary coil reading must be taken with the caps OFF, there is a small amount of resistance designed into the cap. In your case your cap may not be connected. Unscrew, cut the wire about 1/4" if you have the length, spray both sides with Deoxit to clean the copper wires and reconnect.

Test the secondary circuit on the coil before putting the caps back on. A new set of caps sometimes makes a big difference especially if they are 30+ years old.

MaxKZ a good thing to do is add your bike information, "77 KZ650 B1" to your profile signature. So that we know exactly what you are referring to. I know the coil reading numbers changed from 77 to 78-80 on the KZ650s.

Two different bikes with sooty plugs and same symptoms. Have you checked the valve adjustments

What spark plugs are you using? If you're using plugs that are a heat range too cold you will experience fouling. Ed

NGK B7ES on my bike (factory spec), checked and adjusted valve shims first thing this season (3 were out of range).

LineArtist wrote: NGK B7ES on my bike (factory spec), checked and adjusted valve shims first thing this season (3 were out of range).

Yes, those plugs are the correct heat range. Ed

swest wrote: Two different bikes with sooty plugs and same symptoms. Have you checked the valve adjustments

So the answer is yes.
Thank you.
Steve