Motorcycle Repair/No Spark


QUESTION: Bill I read your 2005 reply to Jim regarding no spark on his 1970 CT70.  My has also been stored over 20 years.  I replaced the points and condenser. How much cleaning should I do on the magneto system and can I damage it.  Your help would be greatly appreciated.

ANSWER: James, All that is generally needed is a good set of clean point contact faces, set correctly and to remove any rust on the magnet surfaces inside the flywheel to make them spark. Corrosion that could build up inside the ignition switch or a kill switch should be checked/addressed. To turn the engine OFF, the ignition switch grounds out the coil. If you are having spark problems disconnect the ignition switch and check again. New points can have a layer of corrosion protection on the contacts which will keep them from making spark, so be sure they are touching metal-to-metal cleanly. for wiring diagrams.

They are pretty sturdy, but failing to use the proper flywheel removal tool can cause some damage.

Bill Silver

---------- FOLLOW-UP ----------

QUESTION: Thanks for the quick reply Bill.  Regarding disconnecting the ignition switch, how is that acomplished? After it is disconnected what is the next step to test if that is the problem? Thanks again!

Answer  to see what it looks like.

Because of the location of the switch it is MUCH more difficult to unplug it as it is on a CT90.

If you follow the wiring diagram and check the wiring with a volt/ohm meter, you might be able to do a test of the switch through the harness, rather than remove everything to get to the switch and plug-in connector. Ignition switch failures are somewhat rare, so I would make sure that all of your other work with cleaning/adjusting points, and cleaning the inside of the flywheel is all correctly done.

Bill Silver

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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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