toning down yzf 426.


11 replies to this topic
  • jordan28

Posted April 10, 2011 - 03:22 PM

#1

hey guys. my names is jordan. i have recently(3-4 months) started riding a yzf 426. great bike but.... i mainly ride woods. i have seen some forums saying to do this and to do that but no clear answer. any suggestions to help me tune down this beast of a machine? thankls, jordan

  • QuietFlight

Posted April 10, 2011 - 04:08 PM

#2

put the stock exhaust back on (if aftermarket) and jet it a bit rich.

  • jordan28

Posted April 10, 2011 - 04:23 PM

#3

ive got an fmf powercore iv. what would the stock exhaust do.

  • QuietFlight

Posted April 10, 2011 - 05:59 PM

#4

take a bit of the edge off the power i suppose. The jetting is the main bit to do with performance.

  • 02WR426Cali

Posted April 10, 2011 - 06:58 PM

#5

The stock YZ pipe wont tone down a 426. They run excellent on stock exhaust. The only way the exhaust will tone it down considerably is to use a stock WR or similar setup that is plugged up, also plug up the airbox with a lid and then jet accordingly.
I would say a flywheel weight or a WR setup is the main thing that will help you out. It will mellow the power a little and let you lug a bit more without stalling in the woods. You can also use different gearing with maybe a 15 tooth front sprocket or a smaller rear sprocket if you can find one. That's not typical for woods riding however, more suited for high speed desert. But it will definitely take the bark and acceleration away.

  • jasen 2007

Posted April 11, 2011 - 02:50 AM

#6

buy a 250f...lol Just kidding. Look into getting a heavier flywheel or a weight for your flywheel. Also look into getting an auto decompress setup if you don't already have it. I had an 01 426, great bike but I hated the manual decompression...

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  • QuietFlight

Posted April 11, 2011 - 05:12 AM

#7

The stock YZ pipe wont tone down a 426. They run excellent on stock exhaust. The only way the exhaust will tone it down considerably is to use a stock WR or similar setup that is plugged up, also plug up the airbox with a lid and then jet accordingly..



LOL!!!!!must be why i see so many 426's with the stock exhaust on them!!!!

  • grayracer513

Posted April 11, 2011 - 02:29 PM

#8

LOL!!!!!must be why i see so many 426's with the stock exhaust on them!!!!

Sarcasm...:cheers:

So many people put aftermarket exhausts on their bikes because they believe it will do some fantastic thing for them, when the truth of the matter with most YZF's (not including the '08-'09 450) that the most you'll ever get is 1 to MAYBE 2 more hp at peak. That means that installing the OEM system in place of an aftermarket pipe will do no more than subtract that same amount.

If you wanted to soften the power considerably more than that, and in a range where you're apt to actually ride the bike, re-time the exhaust cam to WR specs if you have the original, non-automatic decompression cam (reverse the illustrated procedure by advancing your cam rather than retarding it), or use the cam from an '03-'05 WR450 per the DCM Cam Mod instructions. Then add a heavy flywheel weight to help smooth the motor out further.

  • ericaz

Posted April 12, 2011 - 12:53 PM

#9

stay off the throttle

  • Birdy426

Posted April 13, 2011 - 09:14 PM

#10

If you wanted to soften the power considerably more than that, and in a range where you're apt to actually ride the bike, re-time the exhaust cam to WR specs if you have the original, non-automatic decompression cam (reverse the illustrated procedure by advancing your cam rather than retarding it), or use the cam from an '03-'05 WR450 per the DCM Cam Mod instructions. Then add a heavy flywheel weight to help smooth the motor out further.

I was thinking WR tiing as well...a free mod if you don't have the 450 or hotcams autodecomp cam installed...

  • Gunner354

Posted April 14, 2011 - 07:56 AM

#11

Sarcasm...:thumbsup:

So many people put aftermarket exhausts on their bikes because they believe it will do some fantastic thing for them, when the truth of the matter with most YZF's (not including the '08-'09 450) that the most you'll ever get is 1 to MAYBE 2 more hp at peak. That means that installing the OEM system in place of an aftermarket pipe will do no more than subtract that same amount.

If you wanted to soften the power considerably more than that, and in a range where you're apt to actually ride the bike, re-time the exhaust cam to WR specs if you have the original, non-automatic decompression cam (reverse the illustrated procedure by advancing your cam rather than retarding it), or use the cam from an '03-'05 WR450 per the DCM Cam Mod instructions. Then add a heavy flywheel weight to help smooth the motor out further.


Is smoothing out the power just like taking away some of the "snap"?

  • grayracer513

Posted April 14, 2011 - 01:58 PM

#12

I'm pretty sure that's what the OP is after here. But there does not necessarily have to be a loss of power associated with that. The "bomb" headers from FMF and others usually bring about a widening and flattening of the power curve, more by extending it downward and slightly upward than by reducing the peak, and on a bike like the '03 YZ450, that can "smooth out" the power delivery considerably by taking the spike out of it. Not so much in a 426 though.





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