Strange problem with misfiring

[Pete]

Hi all,

I've recently encountered a problem, possibly electrical with my '91 750 C1.

The bike has been running beautifully for along time but a few weeks ago I tried to start her up and found that cylinders 1 and 3 weren't firing. I took out the plugs which were wet, cleaned them up and tried again and the bike was fine. This problem happened again last weekend and it occurred to me that it might be a fuel problem as I was almost on reserve. I cleaned up the plugs and went to a local petrol station to fill up, then went for a 30 minute ride and the bike didn't miss a beat.

I was going to go for a ride again yesterday and surprise surprise the bike was missing again, but only on cylinder 1. This time I unplugged the HT lead to confirm it was cylinder 1. This time i noticed that if i hold the HT lead near the plug so that i can hear it sparking the cyllinder fires, but as soon as i plug it onto the spark plug it starts missing again. i can repeat this with the same result.

The bike has a new battery and i had the valve clearances/carby balancing done a couple of months ago.

Has anyone encountered this before?

Cheers,

Pete.

PS: I bought another bike at the same time this started happening, jealously perhaps?

[Shedman]

Hi Pete, definitely jealousy! Have you had a voltmeter on the coils? Its in the Haynes manual on how to check them, elecktrickery testing is something I only do with a manual because otherwise I'd probably lose a few body parts. If the HT leads and plug caps are old I'd replace them anyway, same with the plugs. Are you getting a spark on each cylinder with the plug laid on the head? If everything doesn't check out ok, then check the earth connection on your coils for corrosion.
I bought a non running 750 Zephyr a couple of years ago that had intermittent sparks on different cylinders, it would never run on all four at the same time, it turned out to be the wiring from the pick up coils in the right hand side of the engine, the brass inside the connector blocks, behind the right side panel, were green and furry and once cleaned up the bike ran superbly.

[Pete]

Thanks for the advice,

The leads and plug caps are only a couple of years old and I just replaced the plugs. I spoke to a mechanic at a local Kawasaki dealer and he said my problem was caused by the iridium plugs I was using. I swapped them out for standard ngk’s and it was fine. I went for a ride two days ago and it was good but when I started it up today it was missing again.

I had a quick look at the idle mix and they were all out about 5 turns. Number 3 looked like it was about to fall out!

I took them back in to 2 turns but the missing was still happening mainly on cylinder 1. If I unplug the lead and leave it loosely sitting on the plug it runs fine but as soon as I plug the cap on properly it misses.

Ill have another look at the coils tomorrow.

Thanks

Pete.

[Freddy]

I spoke to a mechanic at a local Kawasaki dealer and he said my problem was caused by the iridium plugs I was using.

The dealer guy is talking through his arse. I've been using iridium spark plugs in my D1 exclusively for years.

My thoughts, unless you have complete confidence the carburetors are 100% you could be chasing your tail for ages. As blocked carbies is a common problem on bikes used infrequently or seasonally, I pull the carbies off and give them a thorough clean. Even if its not the problem its still a worthwhile exercise as they probably haven't been done for years and due for a good clean. But the main thing is you'll have eliminated the fuel side of possible causes.

P.S. And for what its worth, I think in another thread you mention you have a Stage 1 jet kit fitted. Personally I'd bin that and return to genuine Keihin jets. As it stands you haven't a clue what size jets are in that kit, or the quality. I would only ever use genuine parts in the carburetors, and that includes float valves. The only parts I ever uses from chap ebay kits is the o-rings, and the pesky tiny flat washer that sits together with the o-ring in the pilot screw. Both will remain in the carby body when you take the pilot screw out and may get lost if you aren't aware they are there. They are tricky to actually get out without loosing them, being so small and fiddly.

[Pete]

Hi all,

I took everyones advice and looked at pretty much everything. I removed the tank to discover that the right coil wasn't earthing correctly. I tightened everything back up and reseated the leads check the plugs, gap, idle mix, fuels filters etc and at the end the bike is now running very nicely.

Thanks for all your help guys.

Cheers,

Pete.