426 - or - 450 how do I tell

7 replies to this topic
  • ThumpDave

Posted July 28, 2004 - 05:49 PM


I just purchaced a 2001 426 and the guy I bought it from said that it had a BIG-BORE kit. he didnt know anything about it and didnt have enought knowledge to tell.

I can tell that the JUG looks differnt from the rest of the head its not the stock piston jug

Is there a way I can tell that it had been bored and how do I tell whether or not its a 450 bore.

In what I have read and seen the only option in boring from a 426 is to a 450 and likewize the bore from a 400 is only to a 426.

all suggestions welcome (where do I start

Thanks Dave :thumbsup:

  • yz426onNOS

Posted July 28, 2004 - 06:29 PM


Tear it down and break out the measuring device.

  • ThumpDave

Posted July 28, 2004 - 06:33 PM


not much help. Would there be any Identification markers on the new jug?

  • DoctorRzed

Posted July 29, 2004 - 12:58 AM


post a pic :thumbsup:

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  • ThumpDave

Posted July 29, 2004 - 05:17 PM


on the cylinder jug the numbers 5JG00 / 426 cm (3 cubed)

on the head somebody etched in 19799 and 68M89

Hope that helps
If you still need I'll post some pics

Thanks Dave :thumbsup:

  • gonzo

Posted July 30, 2004 - 01:04 AM


Those are the factory numbers. If it's bored out those wont help. You will have to measure it. Also remember that the 450's now are stroked 426's not bored. So anything over 92mm and you know it's bored.

  • Satch0922

Posted July 30, 2004 - 02:33 PM


all you will get on a 426 with standard stroke is 440cc if you bore it out.

  • brucifer

Posted July 30, 2004 - 05:11 PM


Standard bore for the 426 and 450 are 95mm. 426 stroke is 60.1mm and 450 stroke is 63.?mm. the best way to check the bore is to pull off the head. Do that when you need to rering the bike. When do you rering the bike? Do a compression check now. And when it starts falling in pressure check to bore. IMO :thumbsup:

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