Overweight Wiseco 87mm Pistons

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Gardner
Diana
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Joined: Thu Jul 17, 2008 6:09 am
Location: Davenport, Ia

Overweight Wiseco 87mm Pistons

Post by Gardner » Tue Apr 02, 2019 7:46 pm

Four years ago I pulled my SS engine over the winter and bored the cylinders for 87mm Wiseco pistons. Online research revealed crank balancing would give a smooth running engine. Others said all they did was bore cylinders, swap pistons and the engine was smooth as ever. I decided to go the quick and easy route - bore and swap. The engine ran great but the vibration was so unpleasant I only rode the bike 300 miles that summer. The next winter I pulled the engine and compared piston weights, stock 86mm piston including rings, pin and retainers is 473.6 grams. The Wiseco 87mm piston with all the same pieces is 571.0 grams. Does anyone know why Wiseco would make pistons almost 100 grams heavier? Did they get some odd piston 40 years ago and they still make them like that one? I doubt if you could add enough heavy metal to the crank wheels to balance both pistons. I run CNC milling machines all day so I started machining the Wiseco's to match the original Ducati pistons. I had to 3D machine the insides, mow the sides of the pistons off, shorten the pin and recut retaining ring grooves. Wiseco does NOT recommend machining their pistons. Got my smooth SS back and put over 8000 miles on the pistons. Here's a pic showing before and after. Something to think about if you're considering going to 87mm.
Image
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2

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Gardner
Diana
Posts: 55
Joined: Thu Jul 17, 2008 6:09 am
Location: Davenport, Ia

Re: Overweight Wiseco 87mm Pistons

Post by Gardner » Wed Apr 03, 2019 5:03 am

Whoops, 90 degree v-twin you only balance for one piston/rod assembly. Still, 100 grams seems excessive for a replacement piston.
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2

ducadini
750 Sport [BEVEL]
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Re: Overweight Wiseco 87mm Pistons

Post by ducadini » Thu Apr 04, 2019 12:48 am

NICE work :-D
You would almost say Wiseco forgot to machine them before putting them in the box.
Keep up the good works.

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

jockduck
Mariana
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Location: South Australia

Re: Overweight Wiseco 87mm Pistons

Post by jockduck » Thu Apr 11, 2019 4:58 am

I love your work, does not look like a Wiseco anymore, attached a photo showing the latest Wiseco on the left with the old style Wiseco (1990s) and an original fitment AE. I found the middle one too high a C.R. for road work so I "de-crowned" it in the lathe basically took the bump (5 mm) off the top and its now like the stock SS piston, C.R. is now around 9.6.
Did you use a stock Ducati gudgeon/wrist pin?
Jock
Attachments
2x wiseco 1old.jpg

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Gardner
Diana
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Location: Davenport, Ia

Re: Overweight Wiseco 87mm Pistons

Post by Gardner » Thu Apr 11, 2019 7:24 pm

Thank you Jock, I used the Wiseco pins but faced them off to stock length using black ceramic inserts.
That center Wiseco piston from the 90's looks a lot closer to stock with the skirts machined off and a shorter pin.
So now it looks like they had it right at one time but radically changed the design.
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2

jockduck
Mariana
Posts: 31
Joined: Sun Jan 17, 2010 3:21 am
Location: South Australia

Re: Overweight Wiseco 87mm Pistons

Post by jockduck » Fri Apr 12, 2019 5:20 am

Yes, the earlier type were also available in other sizes too, I have a set of 88 mm Wiseco pistons in my Darmah, which I also "de-crowned" The pistons lost 20 gm in machining from 378 gm to 358 gm, the stock AE weigh 364. I think the modern Wisecos are a bit strange, I suspect they are designed for another engine but they are cheap ! but too heavy.
Jock

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