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Are the darmah pistons interchangable throughout the year ranges? Wiseco lists a piston for the Darmah but only for the 83 model year. Will it fit other years?

The pistons should interchange as they all have 20mm pins. The Wiseco pistons are slightly higher compression than the stock Darmah and SS pistons.

Wiseco lists the 83 900ss and 83 darmah as the same part number. 10:25:1 compresion, 86x74.4 bore and stroke, 87mm bore. My bike is a 79 but I thought all the 900 twins pistons were interchangable? What could be different? Also, my bike is kick only, think the higher compresion could be an issue for starting?

I put Omega high comp pistons in my GTS. These are a high quality forged piston and they have been in there for some years now. At that time I considered Wisco pistons but shyed away as the weight of the piston was quite a bit heavier than standard. (I went to my friendly local jeweler who had an accurate scale.) It`s easy enough to kickstart however if I was to do it all again I would stick to standard. Main reasons being she will ping at higher RPM/loads. I`ve put this down to petrol quality as some brands seem to do it worse than others. Increased load on the big end, which I don`t think any bevel drive needs and last but not least.......I don`t think it went that much harder at all. I guess I`m trying to say it was`nt worth the negatives to gain the small amount of positive.

The Wiseco pistons are heavier but unless you are running the poop out of it you probably won't notice a difference. I ran them in my 900SS for a few seasons and had no problems. You could try Syds Cycles in Fla. Malcome might have some pistons to fit.

I put one oversize Wiseco's in my 78 darmah about 3000km ago. Bike's never run better in the near 30 years i've had it and kickstarting is fine.

Sorry, what I meant to type was one mm oversize, so the 87mm you were referring to was what I used - I don't have the part number with me, but assume it is WISECO 4627M08700. My apologies for any confusion caused.

They work fine, no changes to vibration that i can detect. I don't get up to red line revs on that bike these days, so don't know what happens up there, but it's nice and smooth to 6000 rpm. The extra compression (Both from the higher compression piston, but mainly from refreshing a tired bore and piston) isn't noticable with kickstarting, but it sure makes your Conti's sound better!

I saw a decent price for em here..

http://cgi.ebay.com/ebaymotors/DUCATI-D ... 0273502728

Cheaper then I paid, anyway.

Thats a great price for anyone doing up an engine at only US$128 each with pin,rings and clips what a bargain

So even though those are listed for an 83 model year they will fit my 79 without problems? I thought the 83 was nikasil lined, therefore it wouldnt work in my bike. How far can you overbore one of these cylinders? I am full of questions about this because i dont want to make an expensive mistake on my first bevel rebuild.....

They will fit just fine. The rings provided have a chrome faced top ring which is for cast iron bores. 87mm is about the most you can bore the stock sleeves and maintain a good wall thickness. The nice thing about the iron sleeves is they are easily replaced and not real expensive.

I was just old dealer cost is $140 so that ebay ad is below cost... a super deal.

I got my pistons tonight. They are quite a bit different than the stock ones. The sides of the pistons are not machined out like the stock ones. They are a bout 1/16 inch higher than stock (high compresion) but the valve pockets seem to be plenty deep. I think the biggest reason for the wiscoes added weight is the wrist pin length. Since the piston isnt machined out on the side the wrist pin needs to be longer to pass through. When you hold them side by side in your hans the pistons themselves feel very close in weight. But when you hold the wrist pin in your hands side by side the wiscoes pin is MUCH heavier. Wish I had a scale for actual numbers. Why would they machine them this way? Are both styles equally functional? I took some pics...sorry for the blurry ones but you get the idea.

http://picasaweb.google.com/mizike77/Wi ... #slideshow