Anyone else has this issue?
Looks like it may have left the factory with the keyway being on the extremities of a proper transition fit....
Interestingly the KTM 640 had tapered woodruff keys on ether side of the crankshaft, which pretty much eliminated the likelyhood of Key / keyway damage.

Original key on left and new key made from 8x8mm key steel on right in attached photos. (7x7mm key steel too loose to make new key from)

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Nice job. That is disappointing.

Thanks Hammer, it may be in vein as I think the big end has gone, and will probably have to change RHS crank and bearings....

I was asking Kev about stripping it, as it keeps shaking the key loose even with loctite 660 (haven�t tried Belzona molecule which is really dear).
Going to inspect with bore camera when it arrives before removing head and splitting crank case.



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Do you already test this key on working engine? Working properly?

Hi AI_T

Been up and running a week (approx 1000 miles) with no problems. made sure key was a tight fit (had to use screwdriver to remove it) also made sure gears were a tight fit as well (but not so tight as to damage bearing when tapping the gears back on the shaft and key).

But will report if and when I have to take it to bits again; but if it does happen will probably most likely do a rebuild and look at doing one of kevs big engine mods and changing piston or piston and crank (raptor crank).
Ideally will look for a s/h engine to rebuild and then at least I have some transport to carry bits to machine shops if unable to machine at home.

Fergus

how did you skim off the 9x9mm steel to the size needed for this woodruff key?
i do believe this misfit from factory, with too much play, ads to loosening the nut.
i'd like to check mine and meanwhile fit the correct woodruf size.

Good old fitting skills or using a file carefully, and then fine sandpaper.
Don’t just file to tolerance and then sand, as more likely than not, you will end up with a clearance fit!
Leave at least 10-15 thou on the key before sanding.
Still used loctite 660 (shake before use) and primer 7240.

If the key gets badly galled, then it is too tight; the use of ‘engineers blue’ will also help highlight any high spots, on the key or keyway.
Also check gear keyways as well as the crankshaft keyway for damage, you may need to lightly deburr the edges, with a grinding stone, but don’t take masses off as this results in reducing the key contact area, and increases point loading.
The crankshaft keyway can be lightly cleaned with a diamond burr; again don’t go mad.

The sanding of the key will help to reduce the likelyhood of galling when placing gears over shaft with key fitted.
Either use standard key steel or 316 (A4) stainless steel.
Filing stainless, do this carefully if using stainless as the key will work harden, then filing will become substantially more difficult.

With either key steel or stainless key steel, use a hack saw and files DO NOT USE POWER TOOLS, except if using a milling machine / lathe, as this uses cold cutting.
Hot cutting will end up work hardening the steel and causing embrittlement.
De-stressing stainless is an arduous task.

Keysteel (mild) can be bought on Amazon and Stainless / mild on eBay, in 6” or 12” lengths.
Not the cheapest, but I don’t have room for a 6m length of keysteel in the house!
Ideally buy 8x7mm key steel, otherwise just get 8x8mm.


>>Make sure the surfaces are clean after you have checked transition clearance fitment.

>>Apply primer to both surfaces and allow to dry (key and key way; and keyway in gears if necessary)

>>Apply loctite 660 (after shaking) to key and keyway (and keyways in gears if necessary).

>>Then fit lockwasher and torque up crankshaft nut to 120Nm.

thanks for this extended manual :-D