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Spark issues

Posted: Thu Sep 07, 2017 11:28 am
by Magnus
Hello!

This relates to my 1984 XJ 600.

This morning it was finally decent weather again so i thought i'd ride into work. However, when i started up the bike it ran very rough and it didn't want to run off the choke and it wouldn't rev more than 4-5k. So i abandoned and took the car (bleh).

Now after work i did some trouble shooting and realised that #4 wasn't firing at all. I took out the spark plug and it was fairly black. Cleaned it and put it back in. Now it started to fire again but on a short test run it didn't want to rev more than 6k.

Since it's been raining for quite a few days i figured maybe the problem really is the hi voltage leads getting moist. The bike is parked in cover but outside. So I took of the cap from the wire and on a hunch I cut off 5-6mm from the end of the lead and screwed the cap back on. This helped and it started running pretty well again. Now it runs perfect at high and mid revs but i get a very intermittent missfire on the right side (probably #4) on low revs, like below 4k. It's hardly noticable when riding but i can clearly hear it if i listen close to the muffler.

So since i know very little about motorcycle electrics i wanted to ask you guys what you think. My plan atm is to change the spark plugs since i have no idea how old they are and also change out the hi voltage leads from the caps to the coils. I figure if trimming off a bit of the lead to the cap seemed to fix most of the problem maybe the leads are really old and needs replacing? It's difficult to tell or know if they are still the original 33 year old leads the came with the bike, if so the rubber covering could be crap by now?

I hope this made sense, english isn't my first language so finding the correct technical words isn't that easy. :)

Now i'm gonna get a beer!

Cheers,
Magnus