Bigger displacement on the 426

7 replies to this topic
  • eduardo426

Posted November 17, 2004 - 12:44 PM



My 426 is tuned with a Wiseco high compression piston and Hotcams and a carburator Kit. I was very pleased with the results but recently my fifht gear failed.

Since i am from Portugal, do US models soffer from such problem? It seems that the material on wich the gears are made is not very reliable, but almost everyone experienced problems only in fifht gear.

Now...back to the issue, is there any manufacturer that sells a kit to raise the displacement of the 426 engine? My goal is not max HP but monster torque.

Thanks fo the help. :cry:

  • terrymc

Posted November 17, 2004 - 12:55 PM


Wiseco sells a 97mm piston in both standard and high compression form and cometic sells the 97mm gasket kit.

I've got it in my WR, with the 450 cam and it is a monster down low, but a little less so on the top end.

  • eduardo426

Posted November 17, 2004 - 01:06 PM


Did you raised your displacement with a larger piston?? So, you had to have your cilinder machined to fit the piston, right?

I was thinkin about using the same diameter but with increased piston travel.
Do you know any manufacturer who can do this??


  • Hamish

Posted November 17, 2004 - 03:11 PM


falicon do a stroker crank for the 450, but it wouldnt be cheap. With an oversize piston it takes it out to 502cc. Not sure if they do one for the 426. Check out

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  • terrymc

Posted November 18, 2004 - 02:12 PM


Yea, larger piston.

SFO mentioned to me that I could use a CRF450 stroker crank from falicon for +2mm and run an extra base gasket. I think that + the bigger piston takes you to about 477 or something like that. I think that you would have a firebreather with a 13.5:1 piston, +2mm on the crank and +2mm on the bore. I wouldn't want to get too far from the truck with that setup, but man it would be a great motard setup.

I had to have my piston bored and replated to accomdate the 97mm piston. I needed it done anyways due to a dropped valve.

  • FaliconKen

Posted November 19, 2004 - 06:16 AM


falicon do a stroker crank for the 450, but it wouldnt be cheap. With an oversize piston it takes it out to 502cc. Not sure if they do one for the 426. Check out

We can stroke the 426 crank +4mm, and like to bore it +2mm. That gives you 488cc. There's not enough room in the cases to go bigger, and you'll have to run a spacer plate, longer cam chain, longer head bolts, and an oil line extension kit.

The 450 can go to 502cc, no spacer plate, etc.


Posted November 19, 2004 - 06:25 PM


Are the 488 as reliable as my 426.If you run stock comp.Do you have to run race fuel with the 488 and stock comp.I would imagine you do with the high comp.right. :cry: :cry: :cry:

  • Hamish

Posted November 20, 2004 - 12:14 AM


as long as you maintain stock compression you can use standard fuel, regardless of what your bore/stroke is. Re: reliability, more cc's = more power = more stress on all components. As the 426 gearbox is suspect at the best of times it'll probably be the first thing to give up the ghost. I don't mean to offend you, but are you really that quick that a 426 with YZ timing and exhaust hasn't got enough grunt for you? Personally I'd upgrade to a 450 before I stroked a 426. I know a guy that has a 2mm over 426 (450cc) , about 14:1, headwork, hot cams blah blah on methanol and it's good for 60HP at the wheel. Maybe thats a better option for you.


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