Big Time Igntion Failure

[addie]

Please Help!
Basically my sons CR85 wasnt sparking. Ive followed the advice given in other threads.
Ive checked spark plug and lead.
Ive changed the Stator - no difference.
Changed CDI - now there is a very weak spark.
Ive now ordered a new pulse coil and am waiting for it to arrive.
Is there anything else I can try? I am getting desperate. I bought the bike as a Xmas present for my son and am frantically trying to get it fixed before. It was working fine but I recently started it and it just died on me.
Hope u can help!!

 

[Ol'89r]

Sounds like you have changed most everything.

Try the simple stuff. Did you use a brand new sparkplug? Many times a fouled sparkplug will show a weak spark when sitting outside the head but will not spark when under pressure.

Check all of the wire connectors. Unplug them and make sure they are clean and free of oxidation. Use a little dielectric grease when plugging them back together. This will waterproof them.

If the frame has been painted, make sure all of the ground, (Earth, to you guys across the big pond) connections are secure and free of paint.

Good luck. :cool:

 

[addie]

Thanks Ol. I'll go through and re-check the connections. New spark plug is fitted. Your right it could be a dodgy earth (ground). Thanks again, soon as I find anything - i'll let u know.

 

[sharky243]

Check the spark plug cap, sometimes they have a built-in resistor in them and it can fail causing weak spark. Also check the main ignition coil for proper resistance in the primary and secondary windings. Try another spark plug, I've seen brand new plugs out of the box be no good. This is rare but a posibility.

 

[Farmer John]

another simple test is disconnect the kill button & then check for spark.
Kill buttons fail too.

 

[txkawboy]

"yes" to all the above, w/my vote being a weak ground; CR's are notorious for dying kill buttons.
Plus:
1. when t-shooting, always remove any and all un-needed parts, in order to completely remove them from the equation---so removing the kill button when having an elec. problem would apply here automatically...
2. buy eric gorr's MX repair book; it will pay for itself many times over.
3. in the meantime, ensure that the magneto has not sheared its woodruff key.
4. find someone w/any CR80 that will let you come over and swap parts until you find your culprit.
5. i always keep a PROVEN good plug around, jic...

 

[addie]

Thanks everyone for the advice. I have changed the pulse coil and all is working great.