Honing wear

[Warkton Tornado No.1]

Actually, I'm trying to figure out how you could have gone from a CR (250?) piston of any of the many variations (minimum bore size Ø 66mm) down to a Ø 64mm piston

May a new liner have been fitted that hasn't been mentioned?

[jonno]

Sorry my mistake the piston number is 2776CD,and states on the box CR250.Its A TS1 with an iron liner.

[Warkton Tornado No.1]

Sorry my mistake the piston number is 2776CD,and states on the box CR250.Its A TS1 with an iron liner.

Wiseco 2776CD is Ø70.5 mm piston ring common to Honda, Husqvarna, Kawasaki, Suzuki & Yamaha. It would be suitable for an iron liner as it is Alloy steel, ferrox coated, chrome faced, internally notched.

The Honda application would be a CR250 from 1973-1980.

I can't suggest an alternative as I have no dimensions of crown, compression height, peg spacing for the CR but Yamaha IT/DT250 might be close.

[jonno]

The rings supplied are 2520CD.

[Warkton Tornado No.1]

You'll have to make up your mind as to what it is that you have.

Thus far, you have stated twice that the rings are: 2520 CD

(That information would appear to be relevant to the liquid cooled Yamaha YFZ350 Banshee Ø64 mm piston.

That must be an old part number for the piston as it’s not in the current catalogue, but the ring part number is current.

2520 CD - Alloy steel, ferrox coated, chrome faced, internally notched)

Clearly, that cannot be the case as Ø 64 mm rings won't work in that bore.

The other part number you supplied (that may have made sense) applies to the piston rings, not piston!

(Wiseco 2776 CD is Ø70.5 mm piston ring common to Honda, Husqvarna, Kawasaki, Suzuki & Yamaha. It would be suitable for an iron liner as it is Alloy steel, ferrox coated, chrome faced, internally notched.

The Honda application would be a CR250 from 1973-1980)

[jonno]

Yes the other part number I took off the box presuming it was the required set of rings. Sorry if that wasnt clearer stated.Ive attached the pics of packaging.

[Warkton Tornado No.1]

If that box is correct for the piston & rings, then the kit is 431M07050 & the intended application is:

CR250R 1978-80 Chrome Bore x Ø70. 5 mm c/w ring set 2776CD

That would certainly make sense & fit if you have had the cylinder bored. However, the bore you have is almost certainly not 'chrome bore'.

(Wiseco list various pistons with over-sizes to suit differing bore materials including cast iron, chrome & Nikasil, so I'm guessing that cylinder refurbishment engineers in USA must either re-plate to regular over-sizes (rather than grading) or the parent material must be a high chromium content in some instances that they are able to machine to an over-size.

The other box & information cannot be anything to do with what you have)

[jonno]

The only other thing I could imagine is that the rings were taken out to check tolerances and put in another bag after the original was lost. Fitting them in the bore gives a decent tolerance.Which still brings us back to the excessive wear.

[jonno]

Well I cant seem to find an original CR piston anywhere,theyre either wiseco or wossner forged pistons.Cant seen to find any wiseco dealers in this country to get some new rings to try,shou ld've left it alone

[Warkton Tornado No.1]

Well I cant seem to find an original CR piston anywhere,theyre either wiseco or wossner forged pistons.Cant seen to find any wiseco dealers in this country to get some new rings to try,shou ld've left it alone

Grampian Motors don't even show any dimensions for that model, so it's unlikely they've ever stocked them.

I don't know what crown dimensions or compression height your current piston has, but you could compare with the DT250 piston & see what's involved to make the change.

[Fred]

Johno try oro2u . I get my wossner piston rings from them for pe250 pistons. Moto duro are good too, I know they do wiseco mx pistons

[jonno]

Ta Fred I had found Moto Duro will look again. Looking at Wiseco spec tolerances they seem slightly bigger than what I have,and that has been mentioned before. So I will look at that as well.

[Scooterlam]

Fwiw when i got a wossner piston for my ts1 200
I was warned by AF they are soft.