Sympathy failure

JoelNelson · Jul 25, 2014

My bike and I felt so bad for Doug's total failure that she decided to drop a valve head off and "vent" my piston. There went my race weekend. No where near as bad as your grenade.

See ya at Mosport Doug
-Joel
p.s. I think you were holding your cam upside down, when I picked it up it was definitely frowning!

Hobot · Jul 25, 2014

Joel that hurts to see so being a real Commando engine racer you indeed have my sympathy. As often and bad as these things break its a wonder any of em left to ride. What keeps us coming back for more?

Dances with Shrapnel · Jul 25, 2014

Hello Joel,

Robins egg blue motif and being from Kitchener that must be a Herb Becker build. Sorry to hear about the carnage.

Dances with Shrapnel · Jul 25, 2014

Hello Joel,

Robins egg blue motif and being from Kitchener that must be a Herb Becker build. Sorry to hear about the carnage.

JoelNelson · Jul 25, 2014

Good eye sir. She's indeed an HB commando. It's no where near as bad/impressive as Mr. Mcrae's explosion. No worries here, it'll be back on the track end of the week.

pete.v · Jul 26, 2014

Just so there is some continuity between these failure threads, I have a spare +.020 piston if you need it, that is if nobody gets too pissed. If someone feel left out, they can have the other.

Doug MacRae · Jul 26, 2014

Hey Joel!

I saw your bike on the bench; looks like you will be up and running in a day or two fortunately. I will see you at Mosport; we temporarily swiped a 20 year old 850 race motor off one of Herb's 'museum' piece racers so I can race Mosport. Tested it on the dyno and it went great. I still owe you for a fairing too.

JoelNelson · Aug 1, 2014

I was upset when I thought my engine was taken out by a $30 valve, turns out it was a $0.30 woodruff key shearing off the camshaft :evil:

^Explosion related gravel.

CanukNortonNut · Aug 2, 2014

JoelNelson said:
I was upset when I thought my engine was taken out by a $30 valve, turns out it was a $0.30 woodruff key shearing off the camshaft :evil:

^Explosion related gravel.

Joel,
That might have been the result of the valve and piston untimely meeting of the metals. Something has to give. The cam probably rotated to the force of the contact despite the chain trying to drive it in the correct direction, which caused the cam woodruff to sheer.
That’s my guess.
Regards,
CNN

acotrel · Aug 2, 2014

Do you usually run it that rich ?

pete.v · Aug 3, 2014

JoelNelson said:
I was upset when I thought my engine was taken out by a $30 valve, turns out it was a $0.30 woodruff key shearing off the camshaft :evil:

I doubt it was the woodruff key either. The sheared key is merely a symptom of the true cause and should be considered part of the "related gravel". A lose cam nut, tight bushing, lubrication issue, cam chain, etc.

B+Bogus · Aug 3, 2014

An unfortunate disaster, but could have been worse I guess.

On the subject of camshafts, I've heard that the chilled iron cams currently available only permit a low torque value for the nut as they can break if torqued to the factory value.

Has anyone else heard of this?

CanukNortonNut · Aug 3, 2014

B+Bogus said:
An unfortunate disaster, but could have been worse I guess.

On the subject of camshafts, I've heard that the chilled iron cams currently available only permit a low torque value for the nut as they can break if torqued to the factory value.

Has anyone else heard of this?

I think Mick Hemmings quoted that someone use an impact gun to tighten up the nut and it snapped. Not a very good way to get a torque value.
Regards,
Thomas
CNN

Sympathy failure

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