TOPIC:

It developed a misfire about a week ago. I checked all the ignition connections first, couldn't find anything wrong. I move on to the carbs and cleaned each one. Again, nothing plugged, everything looked clean. Finally I tested my coils and one coil had bad secondary resistance. It was a new coil still under warranty with Dyna. Dyna tested and confirmed it was bad and gave me a new one. I put the new coil in today and it's still doing the same thing. Misfire that comes and goes. Sometimes it won't run half bad and sometimes it misfires and cuts out under a load.

I'm baffled since I thought I had it licked with the coil. I'm going to change my fuel filters next. They have some crap in them, but not what I would think should block flow.

Any ideas guys?

Did you happen to check the new coil to make sure it wasn't DOA?

did you check your points/condensers? can be a heatsoak thermal issue.

Yeah I checked the secondary on the new coil and it checks fine now.

I no longer have points, I'm on a Dyna electronic that was installed the same time as the coils.

Could a spark plug issue have caused the secondary to fail?

A spark plug is not going to cause the secondary to fail (normally that is), but a bad plug could cause your current problems.

Hmmm, I better cover that base then too. Perhaps when the previous coil went bad the plugs for those cylinders got all fouled up.

first thing that came to mind reading your post was 'bad plug'.
easy enough. swap to another cylinder and see if problem moves
OR just replace it and see if problem goes away

as for wasted spark coils. they do not like to be operated without a load. bad ignition wire, bad plug. wire fell off. all will slowly degrade these coils. it's very difficult to learn that one has become degraded. what happens is that without a load, the potential builds to the point that it exceeds the insulation breakdown inside the coil and makes carbon tracks. these tracks are high enough resistance to be missed when testing the secondary resistance of the coil. about the only trick I know of for finding is to reduce the sparkgap below spec and see if things improve.

Well I just check the #1 and #4 plugs which are the plugs that belong to the replaced coil. They look good. No visual indication of anything wrong. I wanted to check #2 and #3 plugs, but I don't have the appropriate wrench with me here at work.

Could a plug still be bad even if it doesn't look bad? Anything special I should be looking for?

Plug can be bad, brand new from the box!
Cracked center insulator.
Center pin not connected to anything.
Metal whisker inside ceramic.
Knock will kill a plug quickly.

A section of ignition wire can be bad, fresh off the roll.
Plug boot can be bad. Looked at cb350F, kz1000P5, CB350T this AM and only ONE plug boot was 'good' out of the 10.

If pipe is cold, swap plug or replace plug and see what happens.
If pipe is not cold, plug is probably OK...BUT!
If it's got that dry fluffy carbon all over the center insulator, it's not gonna fire properly and bike will run like crap.

Thanks for the info.

All pipes seem to get equally hot. I will probably just replace all the plugs tomorrow and see how it goes. If it still acts up I will replace the fuel filters.

FYI - It's been running great for months prior to this.

Changed all plugs today with brand new B8ES. Still doing the same thing. I could not get ahold of the same type of fuel filters I am using now so I just flow tested my current ones. No problem flowing gas that I can see.

It really feels ignition related the way it cuts out, misfires, backfires, etc. Very different than when it runs out of gas.

I dug into the wiring and started testing voltage to the coils. I found the 4 pin connector for the right start/kill/light switch controls was crumbled. So it's possible I was losing voltage there. Tomorrow I am going to splice in new bullet connectors and see if that helps. I also removed the small blue bridge connector that Dyna gives you with their igntion kits to tap into the yellow/red hot wire and just soldered it into the connector instead. Looks like I'm maybe losing .5 - 1 volt between the battery and the coils. Not sure if this is significant or not.

Post edited by: savedrider, at: 2006/06/08 18:20

do you have another bike with a dyna pickup? you could possibly swap it out and see if the problem follows it... check continuity on all you ignition wires