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Crank nut behind point cover (23mm)

booost

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Hey guys. So today I picked up a 73 cb750 from my neighbor which has been sitting outside for a few years with only 6k original miles. The motor was seized up so I sprayed wd40 down the plug holes and let it soak. After letting it soak I popped off the point cover and began to spin the 23mm nut to spin the crank and un-seize the motor. It broke the motor free. So I then tried to kick start and the first pump didn't start it so I tried again. On the second attempt the kick start was too hard to push down like it was seized again. So I tried to spin the nut again on the crank and it snapped off. I was wondering if anyone knew how important that nut was and if I am totally screwed? I hope someone can help me out!

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You are only to use that nut to turn a free motor when checking timing etc. You DO need it. The big nut was attached to the timing advancer and point lobe. You will now need a new center bolt that threads into the crankshaft(because it looks like it is snapped of also) and you will need the timing advancer(the part with the two nobs that are broke off) You will need to fix the broken stuff before you attempt to start it. The nut and the smaller nut inside of it keeps the advancer indexed onto the crankshaft.
 
Thanks for all the info. Do you think that i can replace the part that threads into the crank without pulling the motor all apart? An where would I be able to find all these parts?!
 
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