Vintage Dirt Bike Q & A

I bought a huge parts lot to help with my bike rebuild, and happen to have a Honda OEM CDI ignition system that appears to fit my 73 CR250M. I think this was option on a later year bike, but I'm not sure about that. Anyway, who knows if there are any issues with installing this CDI on my points bike? And, on top of that, who knows how the CDI will work compared to what appears to a fixed-timing points system with no advance mechanism. Does the CDI have RPM specific timing changes like a modern ignition system? Is this upgrad a good idea?

Thanks! Jon

The CDI ignition was standard on the '74 CR125 and available on the CR250M1 (The Red Striper), both models used the same coil "360" part number.
I don't think that unit will work on the 73/74 CR250M. The M1 had a different cylinder due to the up pipe and probably had different exhaust and
intake ports as well. With the port timing different, the ignition would be designed to operate on a different "map" than the M. Another concern is,
I believe honda upped the compression on the M1 because of the advance feature the CDI provided that was not available on the M. In other words,
if you installed the ignition on your lower compression M and the CDI (by design) advanced the timing at higher RPM, you would actually lose power
compared to the low tech points ignition.

None of the above would apply if Honda offered a CDI ignition option specifically for the '74 CR250M and those were the parts you actually had. I don't
think they did but I could be wrong (wouldn't be the first time). Maybe somebody else here knows the answer to that one.

I would stick to the point ignition unless you had a CDI specifically for your M.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

the CDI was optional on 75 and 76 CR250's here is a pic of a mag on a 75 model,i was setting the timing on it and that is why the multimeter leads and break over bar are there.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Yep, that looks like the points version that came on my 73. It seems like if Honda offered the CDI version as an option, that the points and CDI motors must have been the same - otherwise to order the optional ignition would have required a bunch of motor changes. Since I am done building the motor and actually fired it up successfully last night, I'll leave the points ignition in there. I'll probably try the CDI set up down the road at the fist sign of trouble - or if I feel the need to search for more power.

Thanks, Jon