Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: Ribs on June 22, 2014, 10:49:59 PM

Title: CR 85 loses spark
Post by: Ribs on June 22, 2014, 10:49:59 PM

I've got a spark issue on my 2005 Cr 85rb, here is my problem--the bike runs great then all of a sudden it will stop running(no spark) if I let it sit for 10-20 minutes it will start and run just fine,it does not do this all the time ,it's only happened twice in the last 2 months, is the coil or something overheating..?

Title: CR 85 loses spark
Post by: Stusmoke on June 23, 2014, 01:34:29 AM

Does it consistently do it after 10-20 minutes or is it fine some days? What sound does it make when it dies?

Title: CR 85 loses spark
Post by: Ribs on June 23, 2014, 05:29:56 PM

It sounds like it is running out of fuel,but it is not the fuel if I pull out the plug there is no spark,if I let it sit for 10-20 minutes the spark will magicaly start working.the bike will run great for days,sometimes weeks.ive gone through all the wiring no loose connections that I can find..

Title: CR 85 loses spark
Post by: eprovenzano on June 23, 2014, 05:30:52 PM

I'm working through a similar issue on an old XR100 I'm rebuilding for a friend...  Test all electrical components when the bike is cold...   (Google how to test the electrical components.)  Test the coil, stator output, and output through the CDI, and write down the results.  Take a heat gun / blow dryer and heat up each component, and retest.  Hopefully you will find the the one that's failing. 

Title: CR 85 loses spark
Post by: rlaj1004 on June 24, 2014, 09:05:59 PM

Sounds most definitely heat related. You probably already know this but heat increases resistance, resistance can fault a component or wiring to the point that you lose spark. Have you noticed does it do it quicker on hotter days.

You can improvise on testing procedure eprov recommended. Make sure the bike starts, has spark. Pick a component, heat it up, fire the bike up, turn it off, move to the next one.....
I friggen hate going through electrical test procedures personally.

Title: CR 85 loses spark
Post by: Stusmoke on June 25, 2014, 04:47:53 AM

Quote from: rlaj1004 on June 25, 2014, 04:05:59 AM

Sounds most definitely heat related. You probably already know this but heat increases resistance, resistance can fault a component or wiring to the point that you lose spark. Have you noticed does it do it quicker on hotter days.

You can improvise on testing procedure eprov recommended. Make sure the bike starts, has spark. Pick a component, heat it up, fire the bike up, turn it off, move to the next one.....
I friggen hate going through electrical test procedures personally.

x2 My old CR had no spark consistently so atleast I could just test each component without having to heat the bastard up

Title: CR 85 loses spark
Post by: evo550 on June 25, 2014, 10:38:02 AM

Stator needs to be replaced or rewound...

Title: CR 85 loses spark
Post by: 2old2slow on June 25, 2014, 11:31:01 AM

Check the coil, I had a similar problem and the coil had a hairline crack in it.  When the bike got hot or wet, no spark...