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 Post subject: Rear Pistons
PostPosted: Fri Mar 30, 2018 6:16 pm 
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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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1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
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 Post subject: Re: Rear Pistons
PostPosted: Fri Mar 30, 2018 7:39 pm 
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Location: New zealand
makita do them with windows for the 500 now . yam bits has them
tkrj do them aswell


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 Post subject: Re: Rear Pistons
PostPosted: Fri Mar 30, 2018 9:53 pm 
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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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1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: Rear Pistons
PostPosted: Fri Mar 30, 2018 10:27 pm 
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Joined: Sat Aug 04, 2012 2:29 am
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Location: New zealand
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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 Post subject: Re: Rear Pistons
PostPosted: Sat Mar 31, 2018 5:29 am 
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Joined: Mon Feb 25, 2008 11:44 am
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Location: Northern Ireland
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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 Post subject: Re: Rear Pistons
PostPosted: Sat Mar 31, 2018 5:52 pm 
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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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1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: Rear Pistons
PostPosted: Sat Mar 31, 2018 6:42 pm 
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Location: Toulouse France
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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 Post subject: Re: Rear Pistons
PostPosted: Tue Apr 03, 2018 4:34 am 
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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.

_________________
1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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 Post subject: Re: Rear Pistons
PostPosted: Wed Apr 04, 2018 9:36 am 
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Location: Vienna, Austria
Which TZR model are these pistons from? 2MA?


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 Post subject: Re: Rear Pistons
PostPosted: Wed Apr 04, 2018 5:24 pm 
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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 viewtopic.php?p=65403

_________________
1985 RZ500 1GE Spec
1985 RZ500 47X Spec Project Bike
1986 RG500 ATR
1986 NS400R
1987 TZR250
1988 Honda RC31
2007 DL650 VStrom
2014 Triumph Thruxton Modified


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