#1 header runs cooler than others

After doing some cleaning and oil changing after some fuel in the oil, I'm trying to get my 78 KZ650b back to running.

Both points are firing the coils after cleaning the points.

The #1 plug is firing; checked by pulling the plug, holding the plug agains the head and watching the pretty blue spark appear.

After a bit of a warm up, the number 2, 3 and 4 headers are hot enough to sizzle the spit off a wet finger, but, the #1 just slowly evaporates the spit, and you can tap it with the back of your knuckles and not burn the crap out of your fingers like ya do on 2, 3, and 4 (hence the reason I went with spit coated finger soon afterwards).

When it's running, it idles fine with no hesitation, but, when you grab the throttle, it wants to die until it picks itself up and catches some rpm's. I am also noticing a little puff of black smoke from the #1 and #2 exhaust on the left side.

If you pull the #1 plug wire, it starts to idle a little funny until you put it back on, and it idles fine again.

I've about beat myself silly fixing little electrical gremlins and fuel issues, and I'm pretty sure my carbs are sync'd fine.

What would cause a hesitation in throttle and a much less cooler #1 header with a little bit of black smoke on the left exhaust when goosing the rpm's finally hit?

I just got a KZ650C yesterday and it did that aswell as being power less. It was the exact same cylinder too. I pulled the plug and checked it and it was sparking but weak. I replace all the plugs and it now runs perfect.

Also, you should be able to hear / see RPM's drop when you pull the plug wire from the plug as it's running.

Check the plug gap while you're at it...

Been fighting some similar issues lately. One lesson I learned is that I don't have enough time to wait for a fouled plug to clear itself especially if the engine's not running quite right.

I suggest that you start by being certain that all the plugs are clean and properly gapped. Run the bike up to temperature pull the plugs and read them. That way you'll really know if your current adjustments are effective.

KZCSI

put a timing light on the wire and you can watch and see how it is firing, if you rev the engine and it fires all the time, you may have a carb issue, could be just a dirty piolt jet

have you checked your valve clearances

kc5deb wrote:

...headers are hot enough to sizzle the spit off a wet finger, but, the #1 just slowly evaporates the spit, and you can tap it with the back of your knuckles and not burn the crap out of your fingers like ya do on 2, 3, and 4 (hence the reason I went with spit coated finger soon afterwards)....

Suggest using hand-held water-spray bottle.

Ok, problem is solved.

Compression was ok; #1-130, #2-110, #3-100, #4-130

Plugs were still ok
Coils were shocking the crap out of me.

I guess I didn't clean the jets as well as I thought I did.

All 4 main jets were gunked, but, the #1 was completely gunked shut.

I cleaned both the main and idle jets on all 4 carbs, and I honestly think it runs better now than when I first got it.

It really wants to pull the front tire off the ground, and I think if I leaned back a little, I probably could... But, I'm a chicken, so I'm not...

Thanks all that gave suggestions!

still would be a good idea to check valve clearances since 2 and 3 seem pretty low on compression you should have o more than 10 percent diffrence between cyl., glad you got it running thoughB)