Looking for ideas for fixing a sheared woodruff key

2000 KTM 50 SX SR

Bought it for my son this winter. He had 2 rides on it then suddenly it wouldn't make power and was bogging. Seemed electrical. So I fixed a ground and put a new plug boot on. Good spark, but still bogging under load. Had a funky clutch setup (far from stock) So I rebuilt the clutch and put in some new piston rings. Piston, cylinder and crank were still in mint shape, tight end of tolerances. Rebuilt carb, getting gas good, strong spark, good compression. So the only thing left was timing. Of course I have no manual yet as well so I put a rod down the plug hole and turned the flywheel. Timing definately out. Managed to pull the flywheel pretty easy without a puller, thank god I didn't have to wait to get that...

So sure enough woodruff key is basically dust. No biggie, but in doing so it chipped the crank on the side that gets pressure from spinning. So one side is perfect the other side has maybe a 1/16" of the original edge to hold the woodruff key. Like I said besides this crank is in perfect shape, and I got a 5yr old jonesing to ride at the MX track on Tuesday.

Will JB weld be strong enough to hold the new key in place? Any other ideas on how to build up this area. A new crank will be in this bikes future but I'm looking for some kind of McGyver temporary fix.

Ideas :thumbsup:

I'll post up some pics of it tomorrow.

A new woodruff key maybe???

Yes I plan on getting a new key, it's the damage to the crank's shaft that's the issue....

But now I'm reading the key is really just to locate the flywheel, not keep it from spinning. So maybe I can deal with this.....

The key is for indexing, the taper fit should hold the flywheel on the snout just fine if installed properly and the bolt is torqued to spec (and checked again after a few rides). The surfaces are good (you can lap them) and nothing out of balance.

Install pretty much dry, don't oil the tapers.

The key is for indexing, the taper fit should hold the flywheel on the snout just fine if installed properly and the bolt is torqued to spec (and checked again after a few rides). The surfaces are good (you can lap them) and nothing out of balance.

Install pretty much dry, don't oil the tapers.

Hey thanks alot :thumbsup:

Thats what I was taking from your earlier post and was pretty much my plan for tomorrow. I plan to make a mark on the flywheel I can reference later and as far as my brain can figure with the rotation of the flywheel the worst thing that can happen is it will retard timing.

Should have gone with my earliest thoughts when it was running crappy. Retarded timing, the pipe was getting way hot compared to the cylinder. I guess timing wasn't the only thing that was .........

Well she's back together and fired right up first kick. Holy sh** it goes like snot :confused:

Kinda wish I hadn't put a fresh set of rings in, low on compression would have been good right now, he's in for a whole new animal....

MA springs work great in the clutch, rolls on smooth off idle and still plenty of snap left to get on the pipe.

Another big thanks to Highmarker for helping me sort this out :thumbsup:

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