Vintage Dirt Bike Q & A

Hello,

I thought I would post before I just started replacing random parts. I'm getting no spark on this bike I just bought. The guy I bought it from said that it did run, but just hasn't for a couple years. The wiring looks to be intact. I've tried several known good spark plugs with no luck.

Any ideas on what to check next? Are there any tests that I can do on components instead of just replacing things and playing elimination?


Thanks!

Cheers,
Craig

First, disconnect the kill switch. It will plug into the wiring harness. Just pull out the clip.

If you still don't have spark, check the points and condensor. Make sure the timing is at least close to correct.

After that, you will need to use a volt meter to check the resistance on your spark and stator coils. Not sure what they should be on the MR but someone will know.

Don't forget to get your favorite neighbor to hold the spark plug for you when you kick it over! If he yelps, you at least know you have some current.

good luck,
nola_fiddy

Thanks for the reply!

I took your advise and checked to voltage on the stator with a voltmeter. It would jump up to around 13v upon kicking.

Then, I checked for spark again after reconnecting the stator connector. Bam-- spark. So apparently the stator connector was dirty. I cleaned it off some more and have consistent spark now.

The bike still won't run, but it is already killing my foot and leg because of the compression! It feels like my old 1981 XR500 as far as difficulty to kick. It sounds good turning over!

I think the carb is probably really dirty, so I'm going to take that apart and clean it really well. Then I'm going to get rid of the old gas (not exactly sure where to bring it) and re-mix the fuel/oil. I have my suspicions that it is not at the correct ratio. Stock is 20:1, correct?


Thanks again for the response.

Cheers,
Craig

32:1 is pretty standard on the old bikes like this.

I would be leary of the difficult kicking over. It should not be anywhere near as hard to kick as an xr500. I worked on an old KD100 2-stroke receintly and it was hard to kick. Turned out the main bearings and rod bearings were rusty but not totally locked up.

later,
nola_fiddy