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1975 yz250 piston

06 Jan 2020 18:30
Woodyz250b
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1975 yz250 piston #1
Hello
Trying to figure out how to get my bike up and running. I can't find stock pistons anymore. Was wondering about changing the connecting rod to the 125mm and using a 76 piston. Does anyone know if that will work?

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07 Jan 2020 01:05 07 Jan 2020 01:14 by RT325.
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1975 yz250 piston #2
Just making sure we're talking the right model as "75 was MX250B & "76 YZ250C but mechanically much the same motor with mainly ignition stator change & then suspension of course but same basic motor [i had both new 75 & 76. In saying that--i don't know about rod length changes except from early piston port DT1's to reed DT2's but doubt the YZ's change from "75 to "76 [but could be enlightened. I'll go looking for a piston kit. by stock--do you mean Std Size 70mm. thanks.

Ok here's an example that i'd think would work but be good to have old bits to match with new to be sure. Does list it for an MX250 1975 plus a "76 YZ250 though. Cheers.
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07 Jan 2020 01:49
MarkT
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1975 yz250 piston #3
Try contacting Enduronut for a piston... pm through this forum or This email address is being protected from spambots. You need JavaScript enabled to view it.

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
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07 Jan 2020 05:46 07 Jan 2020 06:04 by Woodyz250b.
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1975 yz250 piston #4
My bike is a 1975 yz250b straptank monoshock. The piston in the yz250a and 250b are different than all others, they shared the same rod length with the 360 then. The piston pin is up closer to the crown. I could continue to use the stock piston if available but I would like to change it to use the more readily available piston design used in the yz250c.
Thanks

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07 Jan 2020 13:26 07 Jan 2020 13:42 by Enduronut.
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1975 yz250 piston #5

MarkT wrote: Try contacting Enduronut for a piston... pm through this forum or This email address is being protected from spambots. You need JavaScript enabled to view it.



.

Thanks Mark, for always steering folks my way . . . .
If people only knew . . . I once had well over $10,000 worth of Yamaha pistons in stock!!

As rare as these early YZ pistons are, Mark is right to suggest contacting me . . . I think I have both the standard "chrome bore" Yamaha piston, as well as some Wiseco oversizes for those who wish to bore and re-plate their cylinders. I'll have to check.

I assume you were needing the standard size Yamaha piston?

.

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You can't accomplish . . . what you haven't dreamed!
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07 Jan 2020 13:53 07 Jan 2020 13:56 by RT325.
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1975 yz250 piston #6
Sorry Enduronut above, i didn't read yours first.

Oh hell, i didn't think of that sorry--& used to race one of those as well. So something super important to be aware of [unless yours has been re-sleeved] is that the 250B runs a chrome bore so the proper ring must be used or it'll be goodby chrome. Made that unforgivable mistake when re-using a gyt kit dt1 cylinder after a lifetime of sitting on the shelf & shuffled through my pistons & rings & ended up with wrong type & one trip down the side of the road & it was history.
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07 Jan 2020 16:44
Woodyz250b
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1975 yz250 piston #7
So, is the rod swap going to work?

I've seen other guys add a 5mm spacer under the cylinder to do the switch to the later piston but I was trying to avoid that.

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08 Jan 2020 15:02
RT325
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1975 yz250 piston #8
just remembered i've got some A & B crank wheels for sale on trademe. They've had a bit of a hard time by the looks with probably piston breaking or rod breaking [unlikely]. tapper looks good. & if my memory serves me right the crankpin on these is one mm bigger & same as the 360 as opposed to the trail 250 being one mm smaller [if that makes sense].
www.trademe.co.nz/Browse/Listing.aspx?id=2477137613

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13 Jan 2020 22:19
Woodyz250b
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1975 yz250 piston #9
Would you be willing to ship those crank parts to Idaho?

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14 Jan 2020 05:17
RT325
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1975 yz250 piston #10
Ok yep could do that. I'd need to go check it out at our local post shop & see if it's viable for you. Our useless dollar value is in 'your' favor though. As you would have read in the auction 'the case doesn't go with it' [mate borrowed it a couple of years ago to use to match something up to--i dunno. Case was not in good condition but if ya desperate i can see if its still around. Cheers.

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