Well I scored it for free and It ran with a little TLC. But one day it quit running....the condenser was bad.
So it got new points, condernsor and NGK plug. Adjusted points to .012 and did a valve adj. to .002.
It ran great then died after a few days.

So i ck'd output at Black wire from points using a test light. It gets brighter the faster i turn the engine. Output of stator is 20VAC....is that in spec? HOw is that even possible? Tested wire up to coil still get a bright light but still not spark. But when hooked up to coil its very dim but does light

OHM tested the coil 2k primary side and 14k on secondary side
Plug cap was intermintent and currently using a known good one from a TRX 125

Now when I hold the plug to the head it arcs from the grd strap of plug to the head. It is not sparking from the grd strap to the electrode.

Im at a lose...I believe its the coil. I can get one of Ebay for $30shipped but its not OEM

 

Hi,
I'm working on an atc 70 for a friend. It's in good shape everything is there but no spark.
It ran ok a few years ago but has sat in his barn the last year. Before I tear into this thing my question is what have you found out on your spark issue. Is there a common part that goes out? Thanks

 

<div class="FTQUOTE"><begin quote>Originally posted by: oneflag

Hi,

I'm working on an atc 70 for a friend. It's in good shape everything is there but no spark.

It ran ok a few years ago but has sat in his barn the last year. Before I tear into this thing my question is what have you found out on your spark issue. Is there a common part that goes out? Thanks</end quote></div>


Well after resetting my points again with a feeler gauge and being real patient....I finally got the spark to be a bright blue.

I bought a Cylmers manual and it has helped alot with diagnosing problems.

 

I'm sure it's the points, they where froze up. I'm getting a spark now so I'm installing new points before putting it back together. I also need tires, they are the originals and they are dry rotted and cracked.
I haven't been on this forum in some time. Pretty good timing on our issue; especially with a vintage bike. Thanks.