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Discussion Starter #2
I'm sending my cylinders off to ferracci thursday to get bored to 944 but idk how.... 4 mm wall
 

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My 540cc SR500's run with a 2mm wall thickness and that's plenty.
 

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If you have anything out of the ordinary I’m sure Feracci will let you know. They’ve probably done about a million of those.
 

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when they go from 92 to 94 the wall gets 1mm thinner, so down to 3mm. the hole in the cases / outside of the cylinders is 100mm.

i have some bruce meyers 94.5mm pistons going into a 900 engine, which will give a 2.75mm wall. generally 2.5 is considered minimum to run. bruce used to run 95mm in the st2, lots of people run 91mm in the small blocks (96mm hole in cases).

there used to be 96mm kits using std 916 cylinders giving 2mm wall, and some of them cracked the spigots off i believe.
 

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Yes I have run and built race motors with Bruces 94.5 pistons no problem , have a set in my monster (low street miles ) and a set in a vintage racer that has probably 5000 track/race miles on them now.

Bruce had the 96mm pistons made for the st2 and they are great in those bikes, may be a tie between the st3 and 966 st2 for favorite ST motor. He did not feel comfortable running them in the air/oil cooled cylinders because they were thinner than HIS comfort zone and he did not see any benefit in taking that chance. He did sell a few sets to some other tuners who then had them replicated by another piston company and sold them for the air/oil cooled bikes. I have not heard of any failures but not everyone tells those tales.

To go big in the 900 cases there was a kit where you get new cylinders with thicker walls and need to bore your cases to fit, very expensive build so not many were done. I do have a couple of these motors and as soon as I have some fresh pistons made I will build and test. One customer has a motor with these that has been fine for many years.
975281
975282
 

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Discussion Starter #9
Can someone clarify the difference/specs of st2,st3, etc.... I have a 1997 Ducati 900ss-sp thanks
 

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Discussion Starter #10
Btw the reason I'm getting the kit is because the vertical cast piston (I believe it was the vertical one) had a hairline crack about quarter inch long in center. Stock=cast/forged pistons.
 

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st-2 is a 944 (94mm ) piston
st-3 is a 1000cc 3 valve piston
you can use st-2 pistons if you get your cylinders bored and replated.
I may have a stock piston if you are interested, I would need a picture of your piston as well as the letter code off of the top ( A,B or C). A 97 piston should be a forged piston but I would want to see a picture of the bottom to verify.
 

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was there anything different about the bike?
turbo?
hydrolocked with water/fuel?

I will check what I have for a 92mm A piston if you are interested, there is a number cast into the bottom I have one in hand marked 09.3582 made by mahle.
My concern would be what caused the crack as that is not normal.
Any chance that's a "casting check" from when it cooled that got by QC at the factory? Is it visible on the underside?
 

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That is just................ohhhh myyyy
Yes I have run and built race motors with Bruces 94.5 pistons no problem , have a set in my monster (low street miles ) and a set in a vintage racer that has probably 5000 track/race miles on them now.

Bruce had the 96mm pistons made for the st2 and they are great in those bikes, may be a tie between the st3 and 966 st2 for favorite ST motor. He did not feel comfortable running them in the air/oil cooled cylinders because they were thinner than HIS comfort zone and he did not see any benefit in taking that chance. He did sell a few sets to some other tuners who then had them replicated by another piston company and sold them for the air/oil cooled bikes. I have not heard of any failures but not everyone tells those tales.

To go big in the 900 cases there was a kit where you get new cylinders with thicker walls and need to bore your cases to fit, very expensive build so not many were done. I do have a couple of these motors and as soon as I have some fresh pistons made I will build and test. One customer has a motor with these that has been fine for many years. View attachment 975281 View attachment 975282
That is just............ohhhhh. myyyyyyy
 

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Discussion Starter #17
was there anything different about the bike?
turbo?
hydrolocked with water/fuel?

I will check what I have for a 92mm A piston if you are interested, there is a number cast into the bottom I have one in hand marked 09.3582 made by mahle.
My concern would be what caused the crack as that is not normal.
No nothing different with the bike always ran good gas in it, it sat for many years before I purchased last year and I appreciate it but no thanks... just going for the 944 conversion
 

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Discussion Starter #18
Any chance that's a "casting check" from when it cooled that got by QC at the factory? Is it visible on the underside?
No it isn't visible from underneath I just kind of assumed of I were to keep running the bike then the crack would start splintering towards the O.D. therefore loss of oil, pressure, etc I hope when I install the new 944 pistons it's okay because they ain't cheap!!
 

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Discussion Starter #20
No worries you will enjoy the 944 kit, just remember with the higher compression you will no longer be able to run "good gas" you will need high octane instead....lol
might have simply been a defective piston from day one.
Thanks man I'm sure I will enjoy it and by good gas I do mean non ethanol and/or higher octane number. What octane do you run in your bikes
 
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