CT90 and Other 6V Ignition Intermittent Spark Fix

Mikerts-Garage

Mikerts-Garage

Member
Hey Y'all, I stumbled upon a revelation yesterday that I haven't seen posted anywhere as far as I know. I've been fighting both my CT90's for a little over a year, essentially they both would cut in and out at higher rpms both accelerating and running down the road. Turning on the headlight would make it worse, having a charged battery and overachieving charging system made it better.

I tried everything to fix this, new battery, new regulator/ rectifier, new ignition coil and condenser, new points, setting the ignition timing a little advanced or a little retarded, nothing helped much. When I could get the bikes running well it felt like a combination of luck and black magic.

So here it is, the magic bullet that solved all my problems: set the points to the low side of spec. Yep. That's it. apparently that increases the dwell time for the ignition coil, and that really matters on these bikes. I was always setting my points to 0.016"(0.4mm) and this made the bike cut out quite a bit, setting it to 0.012"(0.3mm) made all the difference. Both bikes run flawlessly now even with high beam on and no charging system hooked up, Hooray!

I hope this helps some lost soul out there!
 
Hey mikerts, I agree with you. I've had to close up gaps to get the timing correct before as well. The best way to check this is a D cell powered timing light. You can use a 12v one but you have to setup a battery and it's annoying
 
power6994 said:
Hey mikerts, I agree with you. I've had to close up gaps to get the timing correct before as well. The best way to check this is a D cell powered timing light. You can use a 12v one but you have to setup a battery and it's annoying
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I agree, D battery powered timing light is very convenient. I checked the timing both with a 12V light hooked up to a car battery, and the D battery powered light, no difference in performance.

And I'd just like to clarify, It's not that I had to close up the gap to get the ignition timing where I wanted it. I could get the timing correct whether the gap was 0.016 or 0.012, It's that 0.012 lets the ignition coil actually recharge and spark correctly because the points are open for a longer duration every revolution.
 
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