Rear Pistons

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silverstrom
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Rear Pistons

#1 Post by silverstrom » Fri Mar 30, 2018 6:16 pm

Some aftermarket rear pistons do not have windows yet work perfectly fine in the rear cylinders. Knowing that I have to ask; could you use TZR250 pistons for the rear cylinders?

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nzminis
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Re: Rear Pistons

#2 Post by nzminis » Fri Mar 30, 2018 7:39 pm

makita do them with windows for the 500 now . yam bits has them
tkrj do them aswell

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Re: Rear Pistons

#3 Post by silverstrom » Fri Mar 30, 2018 9:53 pm

I've seen them. I'm just curious as to why you can't use TZR pistons if it was possible to use pistons without windows previously. The TZR pistons do have a cut-out. I wonder how much that cut-out could be opened up before strength became a problem?

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nzminis
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Re: Rear Pistons

#4 Post by nzminis » Fri Mar 30, 2018 10:27 pm

would have to look up part numbers . but what was the previous non window pistons origin ?
Rz250 pistons a option aswell ? depends on pin height etc . but they have windows

I have pistons in my bike now with cutouts but 2 10 mm holes above the arch
heaps of meat left around there

have 5k road kms and 1 track day 12k rpm changes all day and they are fine

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Re: Rear Pistons

#5 Post by trix » Sat Mar 31, 2018 5:29 am

Good question. I noticed the mitaka pistons with windows on yambits recently and wondered why they started doing them now after many years of saying that the windows were not needed???

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Re: Rear Pistons

#6 Post by silverstrom » Sat Mar 31, 2018 5:52 pm

In the April issue of Classic Motorcycle Mechanics Stan Stephens says he used TZR piston in RZ500 rear cylinders for years because the cut outs in the TZR pistons were less restrictive than the windows in RZ pistons.

I see no reason why TZR pistons wouldn't work in RZ500 rear cylinders. The ring peg locations are the same, so that isn't an issue. I'm sure you could open up the TZR cut outs for improved flow if desired. TZR pistons also have the added drilled holes for better oiling and cooling, which itself is actually a TDR250 2YK feature.

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phildu31
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Re: Rear Pistons

#7 Post by phildu31 » Sat Mar 31, 2018 6:42 pm

I'm actually remounting my motor with front new pistons in the 4 cylinders.
Another advantage of the TZR250 pistons ( beside half the price of original rears and drilled holes ) is that the piston pin is centered unlike the original rear pistons.

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Re: Rear Pistons

#8 Post by silverstrom » Tue Apr 03, 2018 4:34 am

So we can use 4 TZR pistons. That solves that problem. You can buy 4 TZR piston and ring kits for the price of just the 2 RZ500 rear pistons, if the RZ500 rear pistons can be found. The would also mean 4 Mitaka kits (with rear piston windows) would cost about the same as 4 TZR kits. One other difference being the Mitaka kits come with pins and clips. Yamaha pins are pricey.

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wolfgangh
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Re: Rear Pistons

#9 Post by wolfgangh » Wed Apr 04, 2018 9:36 am

Which TZR model are these pistons from? 2MA?

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Re: Rear Pistons

#10 Post by silverstrom » Wed Apr 04, 2018 5:24 pm

Yes, that's right wolfgangh. 2MA/1KT/2ME.

99999-02108 for the std bore kit with pistons and rings.

99999-02109 for 0.25 oversize kit.

99999-02110 for 0.50 oversize kit.

RZ/RD500 pistons are marked (embossed) 47X00 behind the skirt. The 99999- piston and ring kits are embossed 47X01 inside the skirts. That implies they are actually RZ/RD500 kits that also fit the TZR250.

An RZ500 std bore piston p/n 47X-11642-00-35 is embossed 47X00 behind the skirt. A std bore kit, p/n 99999-02108 is embossed 47X01 behind the skirt. I have both sitting on my desk now.

Some useful information here http://www.rzrd500.com/500phpBB3/viewtopic.php?p=65403" onclick="window.open(this.href);return false;

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