I really should use a torque wrench after my normal long bar plus extension tightening just to see where it's at. I'm guessing i'm past 65 & more like one for every year of my life--74 lol. Be good to know how high you can safely go. Some of my bikes have pretty bad crank tapers from other peoples previous damage, but don't slip. Think i used to torque the 10mm thread head bolts to 40. Not sure what's recommended.

I've never snapped a Yamaha crank. Have seen it happen on other bikes though.

Mid-70's Husky's had a habit of shearing keys and snapping the threads off the end of cranks...

When I got my 76 they warned me at Malcolm Smith's and made sure I had the tools to check the torque after 30 minutes. Or I could bring it back and they'd do it. (They did the initial torque check and we ran it in the parking lot long enough to re-torque).

A few months later at a race, a guy showed up from LA with a brand new 77 Husky literally right off the showroom floor... Promptly sheared the key. Their dealer didn't tell them about the re-torque process... I think it was in the manual as was instructions on lapping the taper. The crank got scarred up but they found a key and promptly sheared that one. Then they still didn't try to lap the flywheel to the crank and installed a third key. This time I was over at their pit and explained the torque process and need to clean up the taper... Their solution was to tighten the hell out of the nut... POP it went as the threaded end of the crank broke off. They had a really bad day.

I've used that three step torque-run a couple minutes- torque- run 30 minutes- torque process on every bike I've had since then even though it's probably overkill... Never sheared a key though.

Sound like there’s a fairly narrow window of not tight enough and too tight! I guess what I really should do is buy the proper tool to hold the flywheel and stick to the 55 lb torque and then recheck per Mark T’s protocol after running it a few miles. I was feeling pretty slick with my homemade holding tool but it’s doesn’t hold well enough to confidently hit 55lbs on the nose.

Mark T, probably a dumb question but I’m more of a woodworker than a mechanic... when you retorque, do you just touch it up with some new force to 55 or do you loosen and start over? I’m assuming the first rather than the latter but I’ve found while dumb questions can be humiliating they aren’t as bad as what can happen when you don’t ask. Not looking at it right now but if memory serves it’s a taper and I just want to make sure there isn’t something about that, that is different from something like a head bolt.

I just check the torque. Most of the time the wrench just clicks. Sometimes nut turns a tiny amount before it clicks.

I always wondered why you keep saying this. Then one day after working on my CT1 I went to kick her over a got a puff and not much else. I kicked a few times and got a cough at best and instantly knew what was wrong, that dummy me forgot to torque down the flywheel and now timing was off. Sure enough, i had sheered that woodruff key apart. So keep on posting this PSA (public service announcement in US).

Your advise is golden. When I rebuilt my DT400 I finished the engine on the workbench and installed in the frame. It was a month or two before I finished the bike. Long story short, I chased a spark problem, bought a new cdi box and as a last resort went to pull the flywheel off and found the nut loose and the key sheared off.

Thank you.