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PostPosted: Wed Dec 16, 2015 1:20 pm 
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Has anyone used one of these pistons? I'm thinking of getting an 88mm. Any downside to this type of upgrade?


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PostPosted: Sun Dec 20, 2015 11:18 pm 
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Is there a newer design? I run a 90mm Wiseco piston purchased and installed early last year (2014). I am not complaining.
Choose the guy who does your cylinder prep carefully. These pistons are not tolerant of poor bore jobs or tighter than recommended tolerances.


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PostPosted: Mon Dec 21, 2015 9:53 am 
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Do you have a part number for the piston you're talking about? I was not aware of a new piston either.
RD Bob.


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PostPosted: Fri Dec 25, 2015 12:48 pm 
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Thanks for the replies. The piston I was looking at is this http://www.ebay.com/itm/141616355644?_t ... EBIDX%3AIT. However, I was reading in a "Cycle" magazine that short skirt pistons do not do well in older singles due to better heat transfer with the "bucket" type, full skirt pistons. Also I read here that oversize pistons cause early wear on the cylinder and rod/crank assembly. I am trying to decide whether to kick up the compression 1 point and a 1mm overbore. My bike in question is a '78 SR500E with 15,000 miles on the clock. Has been ridden easy since new. I purchased it many years ago and have just re-aquired it last winter.


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PostPosted: Fri Dec 25, 2015 5:14 pm 
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The piston in the eBay photo is nothing like the piston you will receive. That is a piston from a modern 450 MX bike and is similar to that run in the F1 world. Honestly, no one has made the soup can pistons since the late 80's and I don't miss them. There are many benefits to the newer designs. Way less mass, rings closer to the combustion space, better materials and better expansion characteristics all come to mind. 88mm is only a 1mm overbore and nothing to fret about. You can run the 10:1 on premium petrol with no issues if you pay attention to the piston to chamber clearances. .035" - .040" is what to look for. Don't forget to confirm valve clearances also, .070" minimum on each, more is better.

Please note that 10:1 SCR is the worst (or best case) scenario. I have found you can usually deduct .5 from the SCR if the head is still unmolested. If so, you will likely need to mill it the achieve the P to C clearances listed above. Typical is in the .045" - .055" range, sometimes more.

Paul


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PostPosted: Fri Dec 25, 2015 5:18 pm 
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Ditto what Paul said. I was just double checking the Wiseco site before I posted.
You might want to consider the Wossner also.
RD Bob.


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PostPosted: Fri Dec 25, 2015 8:04 pm 
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Only 15K miles? Unless it is burning oil why not just freshen the valves and get it crisp again. They are a fine street runner at stock in good nick.

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PostPosted: Tue Dec 29, 2015 9:25 am 
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I went with basically the same piston. It looks like this:

Image

As was stated earlier, just make sure the clearance is about .0035". Mine had .0020" stamped on the box and from what I read, that was a printing mistake made by Wiseco and resulted in seizures. I haven't had any problems with the piston but have only put maybe 2k miles on it so far.

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PostPosted: Tue Dec 29, 2015 3:51 pm 
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Thank you for the replies.


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