I recently nearly had a heart attack when I discovered the thread on the crank ,drive side appeared to be knackered !I'd almost decided to split the motor and send the crank of to be sorted when I sent an email to our ever helpful moderator Musky . He suggested i get a split die and with it slacked off run it up and down and see if I could get some thread back .Basically as he said what did I have to lose ? so have a go. I bought the die and after cleaning the first thread with a file got the die on in what I thought was the correct position and then worked slowly backwards and forwards with the die using plenty of oil until I caught the 4 untouched threads after about an hour to would spin from one end to the other and the amount of swarf in the die was amazing .
Cleaned up I whizzed the sprocket and cush drive together without further problems using locktite and washer and split pin.this was the first time I'd used a die and was really pleased with the result and of course the time effort and cash saved as you can imagine many many heartfelt thanks were sent over to Musky.
here are some pictures