Cracked case....seen this?

bruntr · #1 (**permalink**) 06-15-2009, 01:20 PM

Hey all.... well my 966SS split her cases on me yesterday at Barber, got flagged off the track as unknown to me I was loosing oil & burning it on my headers. I get back to the pits I find this huge crack in the engine case. (See pic) Anyone seen one crack here? I never have. Seen lots crack around the mount bolt but never here. I did low slide at the track 2 years ago but have been running bike with no issues since then, till today. Bike still runs perfect, just spews oil now....

Just wondering if anyone has seen one crack here and maybe have some thought on a cause

thanks

motodave · #2 (**permalink**) 06-15-2009, 05:46 PM

Yep seen it many times, Crank is not true/good anymore or at least your main bearings are shot. Could be just to much preload on the crankshaft caused this.
Look at the end of your crank shaft where it goes in the small bearing on the left engine cover and you may find some strange wear patterns. Seen this from 750-900 aircooled to 888-996 and now even a 1098.
Your in the Ducshop area why not have Mark Sutton look at it? hel'l give you the straight scoop.

DucMarauder · #3 (**permalink**) 06-15-2009, 06:50 PM

I've seen this on raced old school air-cooled motors that where pushing close to 100 hp that where raced. I don't disagree with Motodave, but find it somewhat common to 2 valve motors when used in this fashion over time. I've seen a 5-6 cases like this up against a wall.

bruntr · #4 (**permalink**) 06-15-2009, 07:12 PM

Thanks for the input guys, well I took my time setting pre-load and end float on all the engine internals when I built this motor, and crank turned perfect IMHO when I was all done, where it had been binding a bit when I took it apart, so I made sure everything was set perfect.

But some things do come to mind, one I'm making 106HP and have been running it hard on the track for over 3 years, second, main bearings did not fit as good as I would have liked into the case. I prefer a nice snug fit, one side was a bit too loose and it had spun at one point in it's life. I used red loctite to help keep it in place, maybe not the best thing but all I could think of at the time.

I will look at everything when I tear into it, guess it will be a good time to have crank checked for true as well...

So at least I'm not alone on this, and from the sound of it can be a little more common than I thought.... mainly what I was looking for, Thanks again

Jeff H. · #5 (**permalink**) 06-15-2009, 08:59 PM

I know I'm not being of any help here, but best of luck on getting the Duc back up and running at 100%. She's a beaut!

Jeff

marvin · #6 (**permalink**) 06-15-2009, 09:47 PM

What year are your cases? The later cases have a smaller jack shaft bearing on that side so the cases are stronger. Most of us 851/888 guys use ST4 cases although I think any of the later cases are pretty much the same. I just assembled a 94 Monster engine using 99ssie cases and it has the smaller bearing. If you decide to go that route watch for differences like oil pressure relief valve location etc.

JSR29 · #7 (**permalink**) 06-15-2009, 10:15 PM

That's the same place my 955 Corse engine cases used to crack. The Racing Service Manual used to recommend replacement every 1500 miles.
I couldn't afford that but in retrospect the time I crashed from oiling my own front tire probably would have bought a couple of sets of cases.

duczilla · #8 (**permalink**) 06-16-2009, 01:44 AM

My 92 900ss w/944 topend 12.5/1 comp. pistons, pankl Ti rods lightened/balanced crank blah,blah, about 104hp at the back wheel split the cases between the barrels clear across. Crack went from main to main, lifted the back cyl about a 1/4 inch.Something tells me that 30+ more horses might have a little to do with it.
Ducati back when they ran the 916,955,996 etc. in SBK brought a whole container of engines to swap out because the cases couldn't take the strain

bruntr · #9 (**permalink**) 06-17-2009, 12:43 AM

Thanks for all the help, guess this is just a simple case of 100+hp and three years of abuse on the track. Could have been worse had I continued to oil my rear wheel, thanks STT for getting me flagged off the track before things went further south!

Chris at CCW is hooking me up with a spare crank case

so now it's just a matter of getting out in the garage to the 100+ degree heat and getting to work..........

marvin · #10 (**permalink**) 06-17-2009, 03:03 AM

Quote:

Originally Posted by bruntr

Thanks for all the help, guess this is just a simple case of 100+hp and three years of abuse on the track. Could have been worse had I continued to oil my rear wheel, thanks STT for getting me flagged off the track before things went further south!

Chris at CCW is hooking me up with a spare crank case

so now it's just a matter of getting out in the garage to the 100+ degree heat and getting to work..........

Cool! Hope you're getting late model cases! IMHO using early cases is a waste of time and money.

jmmmrm · #11 (**permalink**) 07-04-2009, 07:07 PM

I have also heard of cases being split, but it was with the 984 kits and the machining of the cases to fit the new barrels. I know that when PCS came out wih their turbo, they said that the cases were like the 916's and that the extra HP should not be a concern.

I do have one question though, did you replace the motor mounting bolts with the nichols ones? I have heard of some problems using their brand of motor mounting bolts.

As a side note, I take mine in to get mapped/dyno'd in 2 weeks. I will let you know how that turns out.

Mike