TOPIC:

Hi Folks, My first post. Great to read everyones posts. I have a 78 LTD1000 and #3 spark is not consistant. I have pulled all plugs and turned it over- # 3 has inconsistant and doen't look as strong a spark. I have replaced plug, same thing. I assume probably not a points issue. Wire or the coil??? How do I check? I should add that the plug end is not original, a dealer changed it a couple of years ago. Where can I get a new coil? Should I buy stock or is there better new stuff? Any info would be greatly appreaciated.

Check the resistance between #1 and #4 plug caps. Should match resistance between #2 and #3 caps.

Just for good measure, go to the bike shop and spend $10 on a brand new set of 5k plug caps.

Thanks, How do I check resistance? Scott

I replaced the plug cap and no difference. If the other 3 ar sparking good, does that mean the coil is bad?? scott

kz1000ltd78andhalf wrote:

I replaced the plug cap and no difference. If the other 3 ar sparking good, does that mean the coil is bad?? scott

Hello, Scott! Welcome to KZRider! We're glad you're here!

You did the right thing in checking the quality of spark.

Am guessing the coils are probably okay. Because a bad coil typically fails to fire either plug.

Some basic preliminary items --

Is battery up to snuff (fully charged with proper fluid levels)?
Terminals clean and tight?
Good solid ground connection where wire from negative terminal attaches to engine or frame?

What is voltage across battery terminals with engine off (look for 12 volts)?
What is voltage at coil primary (look for same as battery)?
What is voltage across battery terminals with engine running at 3000-4000 rpm (look for 14-16 volts)?

Might be old deteriorated plugwires or faulty caps.
Would test for leakage by spraying water mist over the plug wires while the engine is running in a dark gargage and watching for sparks (a sure sign of leakage).

If not already done, should also do a compression test (remember to hold throttle wide open during testing).

Good Luck!

I will check this stuff out and give you an update. Thanks a lot. Scott