pistons for parallel 500

If you need technical information or help with your parallel twin Ducati GTL 350/500 or Sport Desmo 350/500 engine - post your FAQs, comments & questions here.
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GONDARMAH
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pistons for parallel 500

Post by GONDARMAH » Tue Oct 06, 2009 9:42 am

I am rebuilding a Ducati 500 Desmo Mototrans and I will need a set of pistons in first or second overside (78,4 or 78,6 mm)

Anyone got a good recommendation??

Gonzalo

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LAZZERI
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pistons for parallel twins

Post by LAZZERI » Tue Oct 06, 2009 1:44 pm

This a good question !
I begin to know about all the web sites and shops who sell NOS parts for these motorbikes and I have never found any piston, standard or oversize for the 500 cc.
I know that Giovanni Gentile (Classic Italian Bikes) have oversize pistons for the 350 engine, that is all.
(but you can find new liners in two different adresses)
So, if somobody knows where there is a chance to get that, thanks very much.
There is also the possibility that some workshop manufactures new pistons like Aprotec (they have a web site) in France, but it is very expensive.
Try there as well, they make pistons on order, any size, if you send an old one for copy:
http://www.roadandrace.com.au/pistons.htm
Nevertheless, on these engines the pistons and liners are quite "long lasting" (strong) and of course it is easyer to get a good second hand set.
That is what I have done on my parallel with new piston rings and it is just fine.
But there is a better and cheaper solution:
-send your pistons to a goog workshop to make them renewed, if necessary the external diameter will be reduced one or two tens of mm.
-buy a pair of new liners and pistons rings from Classic Italian Bikes or Desmo Shop (Germany). This new liners are 77 mm diameter so you can make them rebored to the exact size according to your renewed pistons.
Be carefull at the end with the piston rings diametral gap, if necessary you can adjust that with a file.

Enjoy yourself.
French Ducati enthousiast
Owned many
At the moment busy with a 500 GTV and a 650 Pantah
my web site:
paralleltwins.com

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GONDARMAH
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Post by GONDARMAH » Wed Oct 07, 2009 2:10 am

Thank you for your answer... and congratulations for your web

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GONDARMAH
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Post by GONDARMAH » Wed Oct 07, 2009 3:11 am

I think:

it would be possible to rebore to 80 mm with the same liners?. This would make possible to mount the 750 pistons

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GONDARMAH
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Post by GONDARMAH » Wed Oct 07, 2009 4:10 am

Ok, ok, it´s imposible. The pin isn´t the same

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LAZZERI
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new pistons and rebore

Post by LAZZERI » Thu Oct 08, 2009 12:12 am

Hello !
The maxi you can rebore this liners is 79 mm, if more they become too thin an it is dangerous.
And if you try different pistons you will have problems with the pin diameter and it's position (too high or too low) in the piston.
So the best is to forget that.
I have seen your pictures of cylinder head in "la maneta", beautyfull !
Anyway, if your pistons and liners are within the tolerances, just fit new rings after deglazing the bores and that's it .
Have food fun !
French Ducati enthousiast
Owned many
At the moment busy with a 500 GTV and a 650 Pantah
my web site:
paralleltwins.com

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Eldert
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Post by Eldert » Thu Oct 08, 2009 1:47 pm

If anyone is interested i have one 78 mm piston ( no rings no wristpin and no circlips ) and 2 sets of 78.4 mm piston rings
these items are new and i would like to get 50 euro for the piston and 40 euro for the 2 sets of rings
items are located in the Netherlands ( very close to Giovanni )


Eldert

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LAZZERI
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Post by LAZZERI » Mon Oct 26, 2009 4:59 pm

Hello.

I know a guy who has rebored to 80 mm an fit 600 pantah pistons.
I don't know about the pin diam and piston height but his bike runs like hell in racing.
The cylinder sleeves must be very thin, but it works...

French Ducati enthousiast
Owned many
At the moment busy with a 500 GTV and a 650 Pantah
my web site:
paralleltwins.com

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