02 yz426f big bore

Hi im going to look at a 2002 yz426f with a big bore kit( 449) he says its got an athena cylinder and a weisco piston.. Hows the reliability of a big bore on the bike? Anything i should know about these bikes in general? `


Thanks, brennan

I have never heard of a Athena cylinder for a yz426f. To get close to 449cc it would have to be a 97mm piston for 444cc or 98mm piston for 453cc. The 97mm is the goto big bore for a yz426f and involves boring and replating the stock cylinder The 98mm isn't common and the stock cylinder will need to be sleeved as the walls get to thin. Though 449cc is what a yz450f is stock and Athena cylinders are available for that bike. Do you have any pictures of the bike for sale?

Heres one picture.

Athena makes big bore kits that generally include a cylinder of their own manufacture, and this sometimes allows them to offer the kits in bore diameters larger than what the original barrel can be bored out to.  Outfits such as Luke's Racing and Cylinder Works offer kits based on bored out and replated factory cylinders.   The 444cc kits for the 426 were quite popular for some time, and made by several such outfits.  They were a 3mm over bore.  There may still be some availability, but you may have to send your cylinder in and have it fit to a piston, rather than doing an exchange.

Picture won't load.

Here it is again. Is it possible that it is an athena cylinder And its 449cc or is that bs?

brennan 057.JPG

Can't tell from this side, Athena cylinders have the name cast into the cylinder on the cam chain side. Though from what I can find they were never made for the YZ/WR426. It is possible that it is just a 444cc big bore using a bored stock cylinder. You can get Athena pistons for these bikes though maybe that's what he means.

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