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TOPIC: Whoa what happened here

Whoa what happened here 06 Jan 2019 15:11 #11

  • Prinzy
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The piston says 70 25 and the rings read 1n 25?

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Whoa what happened here 06 Jan 2019 15:18 #12

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Looks like I’m an idiot and that 25 leads me to believe it’s already 1st over

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Whoa what happened here 06 Jan 2019 16:07 #13

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Not that many years ago I got a used cylinder with a bore that looked really good... hone marks were there (not fresh), and was supposed to be standard bore... I measured the bore with a digital caliper and it looked standard... maybe even a little under standard. I ordered a standard piston... it was WAY loose. I dug out my large micrometers and dial bore gauge, the cylinder was not only egg shape but it was a little bigger than I thought... it ended up needing to be bored to 3rd over to clean up. :Ugh

It's really, really hard to measure the bore size accurately without the right tools and experience... I have the tools but it's still a job I trust to the experts.

:Buds

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

Whoa what happened here 06 Jan 2019 16:17 #14

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That’s what I did and I can see that I’m not getting an accurate reading I know. My brother in law runs a motorcycle/machine shop I should quit being stubborn and take it over to him hes got all the right tools he can bore and bar hone but I am correct on saying it’s first over by the 70 25 on the piston right?

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Whoa what happened here 06 Jan 2019 16:18 #15

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Thanks for helping me out I appreciate it

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Whoa what happened here 06 Jan 2019 16:46 #16

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Most all of us are here to help and that is one of the great things about the Yamaha Enduro community. Even Rich poked his head in and I was glad that he did. The general consensus of the community is to allow ENDURONUT to help every time he will save you time money and aggravation when it comes to machine shop work. Not putting down anybody else. He simply is the best. Bar none. There’s no reason that you cannot run that head unless of course you just simply don’t like it. Hop up parts were part of the Johndra and still are ...

You can always put a new set of rings for $15 back on and do another compression test with one base gasket torqued correctly with both heads.

Whatever you decide

a

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MINIBIKESERVICE@AOL.COM 1971 125cc AT1-C (DOROTHEA) 1971 175cc CT1-C (BRANDY) 1970 250cc DT1-C (MONICA) 1973 100cc Hodaka Combat Rat (ABBY NORMAL) 1975 DT400 (BONNIE BELL)
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Whoa what happened here 06 Jan 2019 17:44 #17

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Thanks for the cut n dry version asco. I appreciate everyone’s help. I’ve had quite a few posts the last year or so and while I’m a farm kid and a equipment operator by trade I like to hear what the right way is and the wrong way is and I’m not sure on some things on my enduros since ya know my 250 was made 13 years before I was born ha ha I learn new things every day on here and have a lot of fun building these vintage bikes with the help of this site

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Whoa what happened here 06 Jan 2019 17:46 #18

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It's very likely it's first over... generally that's what "25" means on a piston... and almost certainly if it has "70 25" stamped in it.

Is there a "K" on the piston? Markings inside? The reason I ask is that there might be different rings (not just bore diameter) depending on what piston you have... Yamaha changed the ring style sometimes and you need to know what you have before you can buy the right rings. If you post some pictures of the top and underside of the piston, maybe Enduronut or another DT1 expert will chime in and help identify.

P.S. As far as the GYT head, it's meant to be used in conjunction with the GYT cylinder or a cylinder with equivalent porting... not just on it's own.

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

Whoa what happened here 06 Jan 2019 18:14 #19

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It’s a Yamaha piston . I’m not out there but I think it was like k 68 or something on the front by the arrow and 70 25 on the back

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Whoa what happened here 06 Jan 2019 18:28 #20

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That will be a piston that requires keystone rings , which is p/n 214-11601-13-00
if you decide to bore to next o/s you will need
piston 214-11636-01-00
rings 214-11601-23-00

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