2001 Yz426

11 replies to this topic
  • GONE1445

Posted November 17, 2006 - 10:21 PM


I have had my 426 for a while now and am thinking of puting in a new piston and rings. should I?

it rund great but it is getting up there in years so I figured it couldn't hurt

also should I change the timing chain? I am assumeing its the stock one

bought the bike used

  • justgotmine

Posted November 17, 2006 - 10:28 PM


hell yeah you should, just changing to a domed piston from wisco will up your horse power by alot. it changes the compression from 12.5 to 13.5 and i would only run 100 octane fuel in it too.

  • GONE1445

Posted November 17, 2006 - 11:14 PM


I was thinkin of goin to high comp piston there is a gas station that sells 110 octane torque-o or what ever its called race gas

but I dont think I want to do that since I trail ride and race gas is kinda hard to come by up there

  • yz_for_me

Posted November 17, 2006 - 11:32 PM


I would forget the high comp piston. You may get more power, but chances are (if your like the vast majority of riders) you don't use the power you have. And who wants to buy race gas, especially if your not racing?

That being said, it still may be time for a new piston and rings, but I'd stick to stock just for the reliability and convenience.

Replacing the timing chain is definately a good idea. It's cheap insurance and peace of mind.

  • Florida_426

Posted November 18, 2006 - 08:35 AM


I would agree with the replies. If you don't know how much time is on the motor do a top end rebuild starting with a piston/ring replacement (including gaskets) and replace the timing chain. While the motor is open check the cylinder's bore, the head condition, the valves and springs for tolerance and get that whole top end in shape. Best of luck on the work, I did this and it was money well spent to me.


  • GONE1445

Posted November 18, 2006 - 11:49 AM


yea I gotta go check my valves today I think

I am pretty sure it wont need new valves because it runs great right now and most people with 426's still havent had to adjust there valves yet

but I will probably do a new piston and rings this winter and a timing chain

oh yea will any exhaust systems from a 450 fit on the 426??

like the mega bomb header and 4.1 slip on etc

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  • grayracer513

Posted November 18, 2006 - 02:24 PM


oh yea will any exhaust systems from a 450 fit on the 426??

like the mega bomb header and 4.1 slip on etc


  • GONE1445

Posted November 18, 2006 - 02:34 PM


thanks man I am guessing by that the 03-05 450's header is the same as the 426 meaning a mega bomb will fit?

and the scliencer has to be modded?

  • grayracer513

Posted November 18, 2006 - 02:55 PM


I believe the headers are the same. You should not have to modify the muffler, but occasionally, I've heard that the bends in the mid pipe need a little tweak. Then again, some say it nearly drops on.

  • Florida_426

Posted November 19, 2006 - 06:08 AM


One last thought for the rebuild, get an hour meter like the sendec from their website or Dr.D site (same meter) then you can keep track for oil changes, valve lash checks and top end work. Try www.sendec.com , www.dubachracing.com or better yet the TT store.


  • Satch0922

Posted November 19, 2006 - 08:10 AM


I would pass on the high comp piston. The gain you get is not going to knock your socks off and if an internal mod won't do that....leave it stock.

I would replace the piston, rings and top bearing. I would also replace the cam chain AND tensionor. Set your valves while your in it and you will be good to go for a LONG time.

And as Florida_426 said....get an hour meter if you plan on keeping the bike.

  • GONE1445

Posted November 19, 2006 - 09:15 AM


yea the high comp piston is out not gonna work good with trail riding

thanx for all the help now I just gotta go buy the parts and find time to do it

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