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Old 30-Oct-2006, 01:44 PM
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Question 888sp4 - racing pistons bad idea?

Hi all,

I'm on the scrounge for some more expert advice.

My SP4 suffered a major blow up last year resulting in the bottom half of the engine being replaced with a donor motor.

New pistons were fitted but these weren't standard Ducati items. It turned out that the height from gudgeon pin to crown was slightly more than standard. The solution to this was to raise the barrels by adding more base gaskets.

Initially this seemed like a good solution (in fact according to Steve Wynne, common practice). However, there is an oilway on the crankcases which is only for air cooled engines. This is sealed with an 'O' ring between case and barrel but on this occaision the ring wasn't high enough to seal the joint at the multiple gaskets.

My question is: Can I fit a thicker 'O' ring to take up the extra joint height? Or are there any other options available to me.

At the moment the engine runs sweet but 'bleeds' visibly from the oilway area (which is unnervingly close to the belts) Funnily, the front cylinder is unnaffected.

Any advice would be greatly appreciated.

Cheers

Fred
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Old 30-Oct-2006, 01:49 PM
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What caused the major blow up, Fred?
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Old 30-Oct-2006, 02:40 PM
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Quote:
Originally Posted by fred888
Hi all,


My question is: Can I fit a thicker 'O' ring to take up the extra joint height? Or are there any other options available to me.


If you're going to all the trouble of taking the cylinders off you can just block the oilway off. As you say, it's only there because of the aircooled bikes using the same crankcases need it.

Theres a description of how to do it about halfway down this thread - http://www.moto-one.com.au/performance/888part4.html - something to do with a 4mm grub screw and loctite.

If you're pulling the cylinder anyway seems a lot cheaper than new pistons or more drastic stuff


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Old 30-Oct-2006, 02:41 PM
mikesps mikesps is offline
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Screw a grub screw into the crankcase oil feed and you won't need to worry about the seal. Size is 4mm, if I remember correctly.

Ahh.. wot he said. Slow typing!
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Old 30-Oct-2006, 04:23 PM
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fred888 fred888 is offline
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The bike suffered a snapped crank due to failing main bearings - at 70+mph!! - on a left hander!!!
Thankfully both heads and barrels were untouched as the crank went south.
I think the grub screw method sounds good but as I don't trust myself with this level of job, I'll have to save my pennies and get a pro to do it.
Pity the 'pros' that rebuilt the engine didn't realise that shimming out the cylinders would expose the oilway. (they've gone bust since so there's no-one to complain to).

Thanks for the input guys!

Fred
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Old 30-Oct-2006, 07:02 PM
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Hi, are you the guy i sold the cheap 851 crank to? via the yank 851/888 list.
Steve Robins s.w.
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Old 31-Oct-2006, 10:10 AM
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fred888 fred888 is offline
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No.
I bought a complete motor to replace the devastated bottom end.
The failed crank was original to the SP4.

Fred
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Old 01-Nov-2006, 08:48 AM
loony888 loony888 is offline
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if the pin to deck height is different i'd say you have pistons for a 916. they are the same diameter and very close to the 888 ones but for the pin/deck height. as the others have said, the best way to fix the leak is block off the oilway with a grub screw and be done with it. note that i only know this after scouring the globe for some hi-comp 888 pistons and everyone only having 916 ones. ferracci had the 888 ones (wiseco) and i was very keen to measure them up when they got here to make sure i hadn't been sent the "wrong ones".
paul.
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