YTZ250 is a trike, otherwise known as the TRI-Z

Bore diameter looks to be 68mm, wiseco part number 515M06800 for the standard size kit

23 hours ago, Tillerman6 said:

dannyboi, I think there is a typo in that message.  I never heard of a "YTZ" 250.   I HAVE heard of a YZ 250, and in the years 76-79 you might find a piston that will work for you.

 You should stay off topics that have nothing to do with your old  engine. Everything about a ty 250 mono is different from your old bike. We are talking about an engine that came out in 1984, not 1974. And by the way Dannyboi the TY250R had a standard bore of 68. So you would want at least a 68.25.

Edited April 18, 20197 yr by lineaway

No problem Lineaway, Just trying to help.

Thanks for all the responses guys I really appreciate it, Tillerman6 I will weigh them for you if I go down that route

cheers!

On 4/16/2019 at 3:32 PM, dannyboi said:

I was looking to get it bored out to 70mm, but they say they will need a good couple of goes to take the 3mm off so it’s looking around £120, I bought the piston kit off of wemoto for £35 hoping that would be it

a YTZ standard piston will fit my 67mm bore?

 

thanks

I buy some stuff from Wemoto.

They are an a-ok honest shop to deal with.

However, those pistons they sell for 35 quid for a ty mono are useful as an ashtray - nothing else. You have been warned.

There is a reason why a Wossner/Wiseco piston costs around a hundred quid, and more for a genuine Yamaha item.

Think about it.