running on half!

Hey folks,
here is my first technical post. The bike is a '77 KZ650B, and I don't know too much about it's history except that it sat out in seattle for a few years before coming back to nice dry Reno to sit some more. Surprisingly, sitting on the coast hasn't caused too much visible rust or corrosion.

my problem is this. I have good compression and a leak down test turned out good, also the plugs are getting gas on them, but it seems like the left bank, (cylinders 1 # 2) are not firing because the plugs still look brand new, and that side does not heat up. I tested my coils and sure enough, they are bad.

Although I don't quite get why a bad coil would cause one and two to not fire, since they are set up correctly with one on 1 and 4 and the other on 2 and 3,I plan on replacing them as soon as my bank account allows. While I'm at it I figure I might as well get set up with a dyna s ingnition also to avoid buying a second set of new coils.

My question is whether I should be suspicious of other problems with the charging and ignition system. i'm sure the coils will help, since they have gone bad, but the symptoms don't seem to indicate that coils are my only problem. One thing I want to do is go through all the electrics i can get my hands on and clean up the contacts and such. Anybody have a hint about something else I might want check out or keep an eye out for?

Thanks,
AJ

Hi and welcome to the site.

The 650's are great bikes with a solid engine. The tests you have done are a good start, and getting the electrics squared away can be frustrating.

You don't go into detail about the test you gave the coils, so can you explain further?

I hope you follow your service manual steps in giving the bike a tuneup. It's a good base to start diagnosing from.

You seem to suggest 1 & 2 are not firing, are 3 & 4 firing, or is the engine giving any signs of life? You say the plugs are getting fuel, that's good. Have you gone into any maintenance on the fuel system yet? Tank cleaning, petcock working, fuel lines and fuel filter...and then on to clean carbs?

Last and not least, add your bike and location to your signature, or everyone will forever ask you " What bike we talking about here?"

PS I don't want to forget. In case this is your first bike to bring back from the dead, first thing is to change the old oil and filter, and have a look at what it contains.

Post edited by: OKC_Kent, at: 2006/11/14 13:52

OKC,
thanks for the reply. I did go through the carbs and lines, etc pretty well, rebuilt petcock. So I am confident that they ought to be close enough to run and then fine tune. The starter motor is bad, so i've been kicking it, it takes a LOT of kicks to start it, and once it does the right side warms up real quick, but the left stays maybe just over room temp.
For the coils I did the test between the wires, not between the posts, and i don't remember the specifics, but the resitance was off by a lot.
Also thanks for the tip about my sig.

Was the coil test between the spark plug caps? Did you remove the caps from the wires and test? It seems and I have found true in my experience that the plug wire ends at the caps get corroded. Remove the caps and trim a 1/4" off, to get to new wire, and test again with the caps off.

Try this, I bet it gets you close. A corroded plug wire affects one lead, in your case cylinders 1 & 2. A bad coil affects both wire leads, which doesn't seem to point to bad coils from the description, (it would be 1 & 4 or 2 & 3) I may be wrong, but start there.

You mentioned you plan on swapping to the DYNA S ignition when able to, but in what condition are the points and condensors (gapped properly, no corrosion, etc)?
Also be sure to lube the felt pad while in there, and make sure the advancer turns freely and the return spring for it is functional.

del

I would FIRST swap the 1 & 4 plug wires and the 2 & 3 plug wires. If the problem stays with the 1 & 2 cylinders not firing, swap the plugs themselves. OK... if you do that and the problem stays (as I assume it likely will), then your problem is with the carburetors. The VM24s on your bike have one fuel inlet and it is likely that 1&2 carbs are not operating as they should... perhaps a plug fuel rail or the carbs were not cleaned adequately or assembled wrong. Before doing anything else with the carburetors, go to my web site and check out the "VM Carb Connections" link and make sure they are hooked up properly. If they are, I would disassmeble and reclean and rebuild the carbs. Hopefully it is just and electrical issue as the electrical issue will be either BAD wire connections to the coils, bad plug caps or wires or just bad plugs.

Ok so i took a closer look at the coils and here is what I found. One is different than the other, all of the wires are labeled for the #2 spot and although I know thats not of significance it bugs me, and all were stretched a bit tighter than I would like. 2 of 4 plug caps practically fell off, and the wire at all the caps was kinda torn up and nasty looking.
I snipped all the wires back to get fresh metal and sure enough, there is 14000 resistance through one and 16000 resistance through the other, where it ought to be around 24000 right? (this is from one spark plug lead to the other.) Even if these coils are useable though I will need new wires and caps anyway. Also, even if one of the coils is the right one, who knows what the other came off of and whether I can count on it doing the job.
I think I will replace them both anyway, mostly for peice of mind. Has anyone ever used ACCELL coils? I'd appreciate an opinion.

del