Yamaha tri-z 250 stock piston size

[TrI-ZRidinn]

Hey does anyone know the size of the piston/rings on a stock 85/86 tri-z?

My bottom piston ring fried....left a wear mark on the cylinder....i found a piston that is 69mm on ebay that im looking to buy, and if the stock size is smaller, thats no problem because i can bore my cylinder out for free at my school.......Thx

Chris

[twgranger]

This one on eGay will work for you if you have the stock bore still.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=43977&item=2456807949

[TrI-ZRidinn]

Thx.. Thats the one i was looking at to :) thx for the info and help



-Chris

[TRI-Zbrian]

if u have a groov in your cyclinder as we speak you are prolly going to have to go the next size up piston wise so if i were you i would not by a stock size piston get the next size over and bore it out you are better off starting with a fresh bore

[J.D.]

Stock bore is 68MM. Stroke is also 68MM.

[TrI-ZRidinn]

Oh, the stock bore is 68mm... so is that piston on ebay, the 69mm next size up? Sorry i have no clue about pistons and sizes and what not...Thx


Chris

[TRI-Zbrian]

its 1 mm over or .40 over id look for soemthing else like a .10 over or a .20 over before u went 40 over try to go in the smallest incramints that u can your sleive will last longer that way becasue u will be able to get more life out of it

[J.D.]

Tri-Z's options are
Stock(68MM)
68.25MM(.010)
68.50MM(.020)
68.75(.030)
69(.040)
69.25(.050)
69.50(.060)
69.75(.070)
70(.080)

A max of 2MM overbores. Make it last, because once you get to that point you have to buy a new sleeve(90 bucks), and probably 100 bucks to install it. Or get a new cylinder.

[TrI-ZRidinn]

Thanks alot guys...This helped a lot.


Chris

[TimSr]

My advise is to get it bored first unless you happen to know exactly how far it needs to be bored to remove the groove. Have them bore the minimum necessary to remove the groove (for a forged piston) and then get your Wiseco piston to fit it.