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Author Topic: Which design is the OEM version of a piston for a Yamaha R5  (Read 142 times)

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Offline cowens726

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #1 on: November 13, 2017, 07:51:01 PM »
I'm sure this not much help but my 71 R5 had the Keystone or more standard style rings rather than the Dykes top ring.  Now I am not certain that my pistons are original except that they are standard bore size so I'm assuming they are original.  I'm pretty sure I have asked this question before because I always thought that the R5s had the Dykes rings but I've slept since then and can't remember for sure :sigh:
I don't always ride a four stroke but when I do, I prefer the valves to be desmodromically operated.
M900Sie - Mine
Buell Blast - Wife
71 R5 being built
71 R5 waiting to be built

Offline arnieward

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #2 on: November 14, 2017, 12:17:04 AM »
I'm sure this not much help but my 71 R5 had the Keystone or more standard style rings rather than the Dykes top ring.  Now I am not certain that my pistons are original except that they are standard bore size so I'm assuming they are original.  I'm pretty sure I have asked this question before because I always thought that the R5s had the Dykes rings but I've slept since then and can't remember for sure :sigh:

thanks for the reply. I just pulled apart an R5 and it too had the non-Dykes style although I was told that OEM was Dykes style.  The bore is 64 (or less?) which means its an original bore. Maybe they switched to dykes top rings in the very late models right before the RD350.  I know older porsches were infamous for engineering changes in the middle of production years and (sometimes 3 changes in the same part in one year) and to order correct part from dealer you needed to give vin and engine no.  Year didn't matter.  but I don't know for the R5

Offline dalvipravin81

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #3 on: November 14, 2017, 06:12:04 AM »
As per the part number starting 278 .. they are both R5 pistons and they both dont have the ports as well.
I have bought R5 rings(278 ...)  which were keystone type assuming they will fit my RD350 pistons which are having part number 361 ..but those R5 rings were thicker than the groves on the piston...

So to answer as per my knowledge R5 rings were produced both Dyke as well as Keystone type !!

Cheers
Pravin

Offline cowens726

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #4 on: November 14, 2017, 09:18:14 AM »
Well isn't that fun the possibility either Dykes or Keystone rings in an R5.  Finding pistons for these things for a reasonable price is hard enough as it.  It will be interesting to see what is fitted in my other bike whenever I get to it.
I don't always ride a four stroke but when I do, I prefer the valves to be desmodromically operated.
M900Sie - Mine
Buell Blast - Wife
71 R5 being built
71 R5 waiting to be built

Offline 202wagon

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #5 on: November 14, 2017, 12:37:44 PM »
R5s came new with Keystone style rings like what you guys are seeing. Early replacement and overbore size pistons were keystone as well, then they changed the replacement  pistons to dykes style like the RD250/350 (which originally all came w/ dykes top ring). I'm sure they did that to streamline the replacement parts (now same part no. rings for both bikes) and pistons are basically the same minus the intake windows for reeds (RD) from a manufacturing standpoint.
Then years later, Yamaha realized the dykes rings suck and break easily and went back to standard style rings for the RD400. That's it in a nutshell.
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Offline arnieward

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #6 on: November 14, 2017, 02:26:45 PM »
R5s came new with Keystone style rings like what you guys are seeing. Early replacement and overbore size pistons were keystone as well, then they changed the replacement  pistons to dykes style like the RD250/350 (which originally all came w/ dykes top ring). I'm sure they did that to streamline the replacement parts (now same part no. rings for both bikes) and pistons are basically the same minus the intake windows for reeds (RD) from a manufacturing standpoint.
Then years later, Yamaha realized the dykes rings suck and break easily and went back to standard style rings for the RD400. That's it in a nutshell.

That is an interesting topic that bears more exploration.  Which piston type/design is the best wrt longevity and performance.  Maybe I will start a different thread on that. Thanks for that clarification.

Offline MarkT

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Re: Which design is the OEM version of a piston for a Yamaha R5
« Reply #7 on: November 14, 2017, 08:52:34 PM »
202wagon nailed it... 

OEM Yamaha pistons for many bikes had "design changes" that make it a challenge to find rings that match the piston, very annoying.  At least the dykes rings are an easy to spot difference.  On others I've seen Yamaha use a keystone top ring and a standard square second ring.  And then supersede the piston to take two identical rings.   :doh: 

On a related note, HVC Cycle just had Wiseco build them a batch of brand new R5 pistons.
1963 Yamaha YG1-T, 1965 Yamaha MG1-T,  1966 Sears Allstate 250, 1970 Yamaha CT1, 1972 Yamaha R5 - 400 project bike, 1981 Yamaha DT175, 1988 Yamaha DT50, 1990 Yamaha Super-DT50