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RT2/3 piston and rings for cylinder 82,25mm and 81,25mm

27 Nov 2019 02:34 27 Nov 2019 03:28 by Twister.
Twister
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RT2/3 piston and rings for cylinder 82,25mm and 81,25mm #1
Guten Morgen aus Deutschland,

with the super help of Franjo from the forum I am currently overhauling my engine of the RT3. I have several cylinders and pistons but also several problems:

- 1st piston is 80.99mm but with cylinder abouve the tolarance measure - is there any Yamaha or Wiseco piston to fit 81.25mm bore cylinder?
- 2nd piston is 81.88mm (!), also abouve tolarance - anybody know about a piston to fit a 82.25mm bore cylinder?
- 3rd cylinder is a NOS - that is not a problem :-) But there is a problem with the piston and rings that came with the cylinder. The L-Ring is not fitting right and will stick in the piston. Are there differences in the shape of the L-Rings? As I learned from Franjo, there are 2 different borings of the NOS cylinders. I have the smaller bore - if this information matters.

I didn't really want to install the NOS cylinder, but if I can't find pistons and rings for the 1st or 2nd cylinder, then there's nothing else left for me. But because I have a problem with the rings in the NOS cylinder, i can fall back on an original piston from Jo, which is however designed for the larger original size, so i still have to work on the cylinder.
The better choice for me would be a a fresh bore and a set of pistons and rings for the 1st or 2nd cylinder. Unfortunately I don't know a solution for the sizes that go far beyond the 3rd over. Anybody got an idea?

Thanks for sharing!

//Kai

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27 Nov 2019 03:18
RT325
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RT2/3 piston and rings for cylinder 82,25mm and 81,25mm #2
I run a 2X5 82mm piston kit in one of my RT2 or RT3's i had that i've since sold. I've got an 82.25 kit ready to go for one of mine also for safety they need about 5mm off the skirt although i forgot to do it on the last one. I've done a couple of mine over the years. At bdc the skirt gets pretty close to the crank. The one i forgot to shorten must still be going or i'd have heard for sure. They have the YZ cut away on the inlet side & the top of the cutaway is by memory about level with the windows of the RT piston. Probably go better with a boost hole high up on the skirt--think i might've done that. Anyway, is a "79 YZ400F as they longstoked that one year as 400's are normaly 85mm so long stroke & 82mm bore--great model & had one new in "79. Link below for partzilla says unavailable unfortunately. Other ebay link is a 0.75 so you can have a look at least. But probably 0.25 kits on ebay somewhere. Might be other aftermarket kits out there like Wiseco etc.
www.partzilla.com/product/yamaha/2X5-11630-10-00

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27 Nov 2019 03:21
RT325
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RT2/3 piston and rings for cylinder 82,25mm and 81,25mm #3
Just saw the price haha. Think i'd keep looking. When i bought mine many years ago they were dirt cheap so i bought them just to see if they'd fit & match up.

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02 Dec 2019 07:52
Twister
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RT2/3 piston and rings for cylinder 82,25mm and 81,25mm #4
Thank you very much RT325, this could be an option, even if it doesn't seem cheap.
Anybody else have an idea?

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