New Member from Colorado

[Yamayz490]

I have questions on Wiseco pistons, sleeving and bore sizes. I have two '83 YZ490s both with different size bores/pistons.

The first one has a Wiseco piston stamped 020. Does this mean it is .20? If so, is this the standard bore? I would like to put a new piston and rings in this bike. It was not seized. I pulled it apart because this piston has been in the bike for at least 13 years. I bought it used in '92 and had it in storage most of it's life. I just now started racing it in the Ultima class in the AHRMA. I figured it was time for a new piston and rings.

The second bike also has a Wiseco piston but it's stamped 2.0, which according to Wiseco, is the biggest it will go. I need to have the second bike resleeved, correct? If so, who is the best at resleeving these old bikes?

I know the pistons are different sizes because the piston stamped 2.0 will not fit into the cylinder of the first bike. When I take the piston for the first bike and put it in the cylinder for the second bike, it is very loose. So I know that 020 and 2.0 are not the same size piston.

Any help or direction will be appreciated.

 

[Tony Eeds]

Welcome to the site :cool:

Be sure and go to your User CP and update information relating to your location, type of riding, etc. After that grab a spot on the couch and tell us a bit about yourself. How long you have been riding, what kind of riding you prefer, where you are located, etc. We will do our best to hook you up with some fellow dirt bike enthusiasts.

Regarding your question, I checked out the Wiseco site and although they have a catalog page for Yamaha, the page could not be found or the link was dead. I would suggest giving Technical Assistance at 1-440-951-6600. They are the best bet for getting a "totally" correct answer.

Now back to your previously scheduled "Welcome".

Check out the Team DRN Mile High Chapter forum for opportunities to hook up with some fellow DRNers in your area. Also you may want to peruse the Vintage Bikes / Racing Forum for info on your Yamaha.

Again, welcome to the site, and shout if you have any questions!