Spark Plug Failure/New Spark Plug Leads

betenoire · Post by **betenoire** » Wed Feb 21, 2007 6:09 am

Friends:

Twice after working on the Weber carb I have attempted to take the bike around the block for a test run. Both times the bike ran, but shortly after the run began the bike started to run on only one cylinder (No. 2).

Inspection revealed no spark. Replacing spark plug fixed the issue. However, new spark plug seems to have developed the same problem.

As you can see from an earlier post concerning timing issues, I was unable to verify the low speed timing due to the mark jumping around so much at low speed. The timing is fine at high speed. John Slocum replied and said that the issue may be voltage at the plug, and to replace the leads. Given the repeated failure of the spark plug, this seems reasonable as a starting place.

Here are the two questions:

1. Has anyone encountered a loss of spark once the bike is warm? What might account for a loss of spark once temparatures on the bike approach running temparature?

2. Inspection of the spark plug leads and the parts manual make it unclear whether the leads are built into the coil. For obvious reasons I have been reluctant to just pull until it comes out, but I did try removing the plug wire from the coil. It wasn't going to just pop out like the usually do. I've never seen a plug hard wired with a spark plug lead before, but there are several things on this bike I haven't seen before. If the leads do come out, how does one get them out without damaging the lead or the coil?

Thanks for the help.

Brett

streetsurfer · Post by **streetsurfer** » Wed Feb 21, 2007 8:04 am

I had the same issues and converted to Dyna Coils from the stock and the problem was solved. At that point I had decent voltage at the coils and was advised by my dealer to do the coils as they felt the kokusans were weak. As my bike aged I did develop a drop in the voltage in the start circuit. I have now done the upgrade with a relay for the start circuit. It fires off nicely now. I also found my start button contacts were real dirty. If you have a big voltage drop between the battery and fuse block or fuse block and coils then you could benefit from one or two of the wiring upgrades which are very well put forth in this thread of jcslocums.
http://ducatipaso.org/modules.php?name= ... tion+relay

Also to answer you question #1. Yes, mine would start and run and foul when warmed up. Maybe the voltage out of the stock coils was droping off as they warmed up. Not sure the reason it acted that way.

And question#2. I don't recall how the plug end of the wire attaches. I don't think I ever removed mine. Could it be that they are threaded onto a threaded spike coming out of the wire? It seems I have seen that somewhere.

persempre907 · Post by **persempre907** » Wed Feb 21, 2007 9:09 pm

It could be also a too much rich carburetion or a carb failure that might wet the spark plug.
When you changed the spark plug, it was dry, so the bike seemed smooth, but when the bike runs the spark plug starts to wet so you have spark failures.
A thing so happens to a friend of mine who had a carb failure (a warped jet).
Good luck.
Ciao

Post by **jcslocum** » Wed Feb 21, 2007 9:29 pm

So, when the plug fouls out, if you replace the plug or just pull the wire off and stick a plug on it you have spark??

I'm thinking some kind of electrical problem made worse buy elevated temperatures. There was a post somewhere about the pickups melting or something. check this: http://forums.ducatipaso.org/viewtopic. ... pic&t=1584

Do you have a multimeter and know how to use it?

ducinthebay · Post by **ducinthebay** » Thu Feb 22, 2007 6:26 am

Two things;
- The high tension leads do NOT come out of the stock grey coils. Don't attempt to pull them out, you will ruin them. But then again, they may already be bad. You can cut the lead a bit shorter and screw the sparkplug cap back on to get to some fresh wire.

- Coils, as the name infers, are windings of wire. When they get warm, they expand, wires rub, and sometimes they start to short out and won't fire as strongly as they do when cold. When coils start to fail, they often first fail when hot.

1987 - 2007=20 years of living above a hot engine with a lot of vibration. If you haven't replace your coils yet, my crystal ball says that you will soon. Coils are a replaceable item, it may be your time.

Aftermarket coils generally work much better, and it give you a chance to put some good high tension leads on too. I just went through this last year, and it runs much better now.