The biggest piston I've found is a 98mm JE (453cc). It's a special part made from a TL1000 blank, and a bit more of a pain to install than the regular 97mm.

You can also increase the stroke by 4mm, which will give you a max of 484cc. However, rod life becomes a significant factor...

HTH, JonE.

Know anyplace that does that modification?

I'm in the UK, afraid I don't have any suggestions for getting the parts in the US.

Sadly the British distributor (Phil Allen) passed away a couple of weeks ago, but you could try this German site for info... www.bergos.de


[ February 20, 2002: Message edited by: Jon Escombe ]

Change the rod to something else I did. The yamaha needs more stroke and a longer rod.

What is the biggest big bore they make for the old 426? Who makes it? $? what all MAJOR modifications do you have to make? I don't want to have to make HUGE modifications. The biggest I've found so far is a Wiseco 450cc kit. was wanting like a 500......



This guy proved his worth to me many time in the past for Honda strokers. Back in the hayday of XL-250 and XL-350's these were the stuff. The guy does great work. Cant vouch for the 440 yz stroker kit though

Be careful, the biggest baddest will also give you the shortest lifespan as others have attempted.

The 450 kit seems to hold up real well.

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