more stupid questions

[Jim]

to those in the know....?in my little yz125 project wots gunna happen if i put a H piston and ring in where a piston and 2 rings were off an E .everything measures the same ...did the heads have different porting...?.or is she gunna go bang...jim... 

[jimg1au]

i guy at work back in the day put a 2 ring in place of the 1 ring
i think his bike was a j its water cooled
and still under his house all wrapped up in a tarp along side the 80
jim

[firko]

I run only one ring on my two ring DT1 piston in the DT1 from Hell. No problemo. Is that what you're asking? If the one ring piston is the same dimensions as the two ringer it should be fine.

[Noel]

The one or 2 rings are not the issue,
what is more important is where the ring gap is ,
If you have both pistons slide the Gudgeon pin into both and check deck and skirt dimensions and take note of where the pins for ring location are and go from there.

Noel

[Nathan S]

Yamaha had different part numbers for virtually every year od YZ125 from 1974 to 1985. Apart from the chrome-bore-specific ring for the A, I haven't been able to pick a difference that matters between them.

There were differences in ring number and ring thickness and very minor differences in piston crown and intake cut-away - but I'm yet to find a situation where they cause a problem.
As Noel says, check the ring end gap, and make sure it doesn't go over a port - if it doesn't then you're pretty safe.

[Jim]

thanks for the input guys i was unsure of it grabbing i will get the head bloke to have a look also, but its good ask and see if anybody had done it before. the ring numbers r the same and the guy i bought them off said he used to use them in go-garts in the early eighties and that they pedaled along quite fine with a bit of surging in corners which some jetting fixed up.as this is for the grandson we are a bit from the track yet.so we shall use the old suck it and see method....
thanks again....jim....   

[matcho mick]

compare the "transfer ports" on the gudgeon pin reliefs on the 2 pistons,a trap for the unwary ,

[Curly3]

And there I was thinking Mick was gunna give a stupid answere.
Doh.

[matcho mick]

i can be serious,(err not for long but  )

[Jim]

thanks mick