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Motorcycle Repair/CT70 minitrail bike


Hello once again Mr. Silver.  I asked a question last month about this trailbike and wanted to ask a similar question if i may.  On this minitrail bike I have replaced points and condenser in it. When i had originally removed both coils from behind its flywheel i tested them for resistance.  They all seemed to be within specs.  I also checked the external coil's resistance and confirmed that the values where just below the 2.1 ohms that the manual suggested.  I am going to purchase a replacement coil for this but wanted to be sure all other ideas were done.  Original wiring checks out ok.  I had assembled this bike and left the external coil unmounted to verify spark which i had gotten.  After reassembly no spark.  All wires are in good shape from what i can see.  Any other ideas to test before i give up on this coil.  Magnets are good and keyway is good.  Thanks ever so much. Sincerly Joe Boscoe

Joe, make sure that the points are completely clean on the contact surfaces and the gap is around .014" or wherever they wind up when the F mark opening occurs. Check when they open/fire and then again a little further in rotation to see that they are opening about .014"  If the points are new and OEM brand, then you should be okay there.

Try removing the coil again to test for spark. If you get it back, then the coil could be shorting to ground internally when mounted to the frame.

Remember that the IGN switch and KILL switch (if you have one) will ground out the sparks. You might try to disconnect the ignition switch and kill switches to see if they are interfering with the spark generation, too.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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