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 Post subject: 96mm pistons in a 650 case?
PostPosted: Fri Feb 23, 2018 5:44 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1802
This engine is for sale on ebay. Looks well worn to me. I can tell it has wide combustion chambers --- probably 104mm across. Looks like it has 96mm pistons! Anyone every heard of that? MikeV

https://www.ebay.com/itm/Ducati-Pantah- ... We&vxp=mtr

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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Fri Feb 23, 2018 7:57 pm 
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Joined: Fri Oct 15, 2010 12:20 pm
Posts: 1275
Location: Vermont, USA
FWIW, seller is a well established Ducati ebay parts supplier, maybe a little pricey....but someone that I've dealt with before and would rate highly. He probably could provide more history on that engine.


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Fri Feb 23, 2018 9:58 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1802
Hay PG. I have dealt with this seller too, and was not questioning his listing.

I know that Lou has suggested that back in the day some builders and racers, er, stretched the rules; some 750s were that, and some might be a tad more.

But that piston says 96mm on top, I think, and I’ve never read of anything that big being used in a Pantah engine. A cylinder spigot would need to be about 102mm, and I think at 100 you are touching the studs.

Just curious if others have ever heard of this.

MikeV


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Sat Feb 24, 2018 12:27 am 
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Joined: Tue Mar 18, 2014 10:03 am
Posts: 359
Hey Mike...
Pressed in liners at 2mms thick would put them right at the edge of the stud hole. There wouldn't be much left of the flange on top to mount the head to though. Sealing at both ends might be an issue.
Regards...
Flattop


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Sat Feb 24, 2018 8:35 am 
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Joined: Mon Jan 21, 2013 4:36 pm
Posts: 205
that'd make it 890.


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Sat Feb 24, 2018 9:55 am 
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Joined: Sun Oct 17, 2010 3:25 am
Posts: 54
Location: Netherlands
could it be 81.96 mm? then the clearance would be 0.04 mm for a 82 mm bore that would be correct for a nicasil cylinder and engine size would be 650 cc

Eldert


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Sat Feb 24, 2018 8:22 pm 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 173
It looks like it could read 89.96mm under the carbon before the 96 it looks like the tail of a 9. As I recall 90mm pistons can be used in a small block. But it is on the edge of the studs and sealing is iffy. I remember hearing stories of pro twin F1's having 90mm vert. cyl. bores because the AMA never bothered to tear down both cylinders. I imagine they shook a tad!


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Sun Feb 25, 2018 11:56 am 
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Joined: Fri Oct 15, 2010 12:20 pm
Posts: 1275
Location: Vermont, USA
Again, maybe run those by the seller?


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Mon Feb 26, 2018 9:44 pm 
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Joined: Tue Oct 05, 2010 9:21 am
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Biggest I've ever "safely" squeezed in is 92 mm and that is with a cast liner.
-Cranky-


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 Post subject: Re: 96mm pistons in a 650 case?
PostPosted: Mon Feb 26, 2018 10:34 pm 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 173
My F1 had 90mm pistons in it when I got it, 820cc as I recall. I built it back to a 750 with thicker sleeves due to the oversized holes and the heads seal really well now and I imagine the bore is a lot more stable now too. Never showed any signs of excessive heating from the thicker liners.


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