compatible motor for my 1981.


Go Slow and Wave at Your Neighbors. Supporter
Reaction score
Good morning and Happy New Year

Planning on building extra engine for my 1981 Special. I found two engines someone is trying to get rid within 10 miles of me.
I realize two types exist in USA depending on year.
What years engines would be compatible with TCI ? I got an extra box real cheap and I tested it and it works.
Can I convert an earlier engine to TCI easily.. I am not ruling out going with points and new ignition.

Thanks again for all your help. The Old Rookie is close to completing his 5000th mile and is having the time of his life !
This winter I will pull the carbs and tank and do a more thorough cleaning. Also, will tighten head bolts if needed on my existing engine.

The existing motor runs well and I don't want to pull it and put my girl off the road for what likely will be a lengthy build.
You gentleman have given of yourself and your sponsoring has been unbelievable.


  • yamaha xs650.JPG
    yamaha xs650.JPG
    429.4 KB · Views: 57
Yes, you would simply swap the alternator and rotor from your current motor on to the "new" motor if it had the older points set-up. You would be looking for what's classified as a "447" motor. They started with the '74 model. The electronic ignition came along in 1980, at least in the States anyway. Your Aussie models may have retained the points for another year. If the motor you get is a '74 or '75, you may need to change the cam chain adjuster to a later one so your banked carb set fits. The adjuster on those two years stuck straight out and had a larger cover nut. It might hit the angle cross bracket on the carb set. The later adjusters angled down a little and had smaller cover nuts .....

Tensioner I.D..jpg

Personally, I would change any type C or D adjuster to a type E.
Are you going to use this new engine in the same bike you are riding now? If so just use the stator and rotor of your bike on the new engine. The TCI uses a set of pick ups mounted on the stator and the rotor has a magnet mounted in the edge. As the rotor turns the magnet passes the pick ups. This triggers the pick ups to send signals to the TCI box. The TCI box uses these signals to determine when to spark.
If you are building another bike to put the new engine in you need your good TCI box, an 80 up rotor and stator and some wiring to hook them together to make them run.