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 Post subject: No. 92 cracked cases
PostPosted: Mon Dec 06, 2010 6:20 am 

Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
What happened to Fran's bike, No. 92 with the cracked cases? (in loudbike)
And how's the injuries ?
Did you find out what caused the crack?

 Post subject: Re: No. 92 cracked cases
PostPosted: Tue Dec 07, 2010 10:16 am 
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Joined: Sat Oct 02, 2010 12:22 pm
Posts: 128

Sorry, I must have nodded off there.

Thanks for asking and there are noteworthy lessons to be related regarding even the newer generations of 750 engines like that M750 (1999) bottom end. I was told these engines were very reliable but start coming apart after about 5 seasons of merciless thrashing. Mine was starting season number eight. Stresses from over-revving (please don't ask) start cracking from a stress-riser at the oil feed hole on the left side of the crank mains which continues to grow both back to the swingarm pivot bore and also forward and around to the opposite side if said merciless thrashing continues.

My engine became a two piece horizontally split set of cases. When the engine finally gave up holding on, a circlip from the accessory (belt pulley) drive spat off and lodged itself into the gears long enough to lock the by now oil-covered rear wheel and spit me off onto Mosport's turn 9. Once the bike was rid of the stupid operator it relaxed, stalled and the heavy circlip dropped free. I woke up some time later strapped to a gurney.

More details if requested but that's essentially it. Newer engines and the 6-speed versions are better in the casting finishing details in terms of stress-risers. People who use more discretion in the revs department (what kinds of revs we be talkin'?) limiting their demands to under 11,000 needn't repeat my adventures.


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