Blow out cause sheared flywheel?!

[drenchedgremlin]

Hello. So i am having a bit of an issue with my titan clone motor. It has a mikuni & governor removed. I was riding around on it , & was accelerating from a stop when my tire blew out and i felt the bike immediately skid to a stop & the motor died. I wheeled it home, thinking nothing of it & put a new tire and tube on. Then went to start it and it would barely fire, And would back fire out the carb and exhaust. I reset valve lash just to be sure. I know it is not the carb since i tried the carb on my other clone and it worked fine, also cleaned the carb anyways to be sure. its not an air leak. Oil level fine. Getting spark. Not sure what else it could be so i am wondering if it is possible that the flywheel key got sheared when the tire blew out? I did a visual exam of the flywheel key without taking the flywheel off, but it didnt look sheared, but i am not sure if one would be able to tell unless you took it off.

 

[Sport King Eric]

Could certainly be a sheared keyway, it could also be a bent Crank. There is a lot of force applied to a very small area when a lock up occurs..

 

[drenchedgremlin]

Could certainly be a sheared keyway, it could also be a bent Crank. There is a lot of force applied to a very small area when a lock up occurs..

Okay thank you. So what is the best way to tell if the crank is bent

 

[SAT]

Check that the flywheel is running as true as it was before. Then, while you have the flywheel off to have a peek, set up a dial indicator. If you indicated it during the build, use the same location and compare notes. If not, report your findings. Then indicate the output shaft end, same rules. Spark plug removed, fuel shut off. Manage the plug wire so as to prevent an accidental fuel-air ignition and/or a shock. Indicating each end is the quickest and easiest way for me to start the head scratching.
If my advice is wonky, I stand corrected.
Hope this helps,
Steve

 

[EVOL Tweety Bird]

Backfiring out of the carb and exhaust is a sign of timing being off,or bent valves. Hopefully it's just a sheared key and not that the piston came up and smacked the valves.

If you were running a cast iron flywheel, I would lean towards the pin shearing. Jamming the crank to a stop would have the flywheel applying a lot of force to the friction fit and key, as it tried to continue rotating.