Crank keyway offset degrees

[Jcary85]

Does anyone happen to know how many degrees the crank keyway is offset from cylinder 1 TDC? I designed a crank and this is the last thing I need to add. Idk why genius Yamaha didn’t just line it up with…. Anything. Figured I’d ask before I go figure out how to measure this…

 

[Jcary85]

ok figured it out (still need to confirm). I believe its 56 degrees before cylinder 1 TDC. I theorize this because the start of the lumps line up exactly with the key on a 760 flywheel. 760 static timing is 56 degrees. I also roughly confirmed it is close to 56 with an angle finder sitting on the keyway. Will post once I properly confirm.

 

[Jcary85]

So it’s not 56. Need to measure somehow but it seems like it might be 64 or 65. Very difficult thing to measure but I have an idea how to do it.

 

[Jcary85]

ok finally got it. Appears to be 66 degrees counterclockwise of top dead center on mag side cylinder. To measure, I found TDC with a dial indicator. I then zeroed my digital angle finder on the top of the cylinder. I then used a straight edge and layed it flat on the keyway and measured. Did this several times and always got 66. O really don’t know any other reasonable way to measure this. Open to suggestions for sure.

 

[fastgtfairlane]

I would think a degree wheel would be most accurate

 

[Jcary85]

I’m not sure how you would do it with a degree wheel?

 

[Quinc]

@OCD Solutions might have it posted on one of his threads?

 

[fastgtfairlane]

if you set up your indicator on cylinder 1 for true tdc, put the degree wheel on the pto side of the crank and lined up a tdc mark. then rigged up a pointer to locate the key slot on the snout. . youd need 2 pointers, one for the degree wheel, and the other for the key slot. line up the degree wheel and tdc together with a pointer set up on the front for the key slot. line up tdc then rotate until the key slot is a tdc and use the degree wheel to record the degrees of rotation you moved. that should locate the key slot.

 

[Jcary85]

You’d need a way to transfer the 0 degree mark to the flywheel snout to do that. I think you’d introduce a lot of inaccuracy doing that. I guess I could use a straight edge to bring the mark down to the hole in the degree wheel

 

[OCD Solutions]

I did some mapping years ago but have no notes on what my marks meant or why I did what I did.
My test bench doesn't have a top end so my measurements likely don't help but you may still be able to reverse engineer or confirm something from my pics.

I know I repeated this exercise later with a fully assembled engine but I haven't been able to find any pics or notes on it.