WR to YZ timing?

SFO

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#2
I am not sure this is the right forum for this topic, but I will give you my 2 cents worth.
I noticed that the midrange hit of the wr timed bike was dramatically reduced with the yz timing.
It seems to pull harder on top.
It is a straight forward change to make.(The timing)
I like the soft midrange response of the yz timing.
It has made the bike easier to keep out of the trees.
I still run the stock pipe as well. My jetting is still stock.
I have heard that a aftermarket pipe makes the timing change work better.
I just hate throwing away a nice fitting stainless exhaust system.
 

Jonny426

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#3
426 cam timing

I've read somewhere that Yamaha timed the '01 WR and YZ engines the same. I know the 400's were timed differently,but the 426's were now set up the same.SFO did you just retime your cams assuming they were still set up like the 400, or was I misinformed? ( I thought I read this in DIRT RIDER ) Jonny 426
 

SFO

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#4
The wr is still timed differently than the yz.
Rick Sieman said in his website that they were the same but this has since been proven false.
The timing marks that they refer to on the 400 are the same to the 426.
There are complete blow by blow instructions on Thumpertalk.com, that is what I followed.
 

wayneo426

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#5
?

SFO, Are you happy with the change overall? And do you now have more of a hit, and a quicker revving engine w/ the YZ timing? Do you like mx'ing the WR more now? Just want to be sure what Im getting with the change. I know I can always go back if I dont like it.
 

Jonny426

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#6
WR timing

Thanks SFO, I will retiming my toy first chance I get because too much power is only a myth,perpetrated by jealous 125 riders. I am also fond of the nice stainless exhaust Yamaha gave us,but I'm looking for anybody who has a vortip or Baja designs insert in their 426. my bike really likes to run with the quiet insert removed, but is just too loud for my area.anybody running either one? Jonny 426
 

MWEISSEN

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#7
Re: WR timing

Originally posted by Jonny426
....I'm looking for anybody who has a vortip or Baja designs insert in their 426. my bike really likes to run with the quiet insert removed, but is just too loud for my area
I've run the Vortip in my WR400 for a couple years. It's comparable in low-end response to the uncorked exhaust, and passes 94 dB sound tests (92.7 max at my last check). Put it in, you'll be much happier.
 

SFO

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#8
wr vs. yz timing.
I would like to see the real numbers on a dyno.
It is 50/50, for me.
For woods/tight stuff I like the wr timing better.
For more open 4th-5th gear stuff I like the yz timing.
People swear by the yz timing, but I can't say it is everything for me.
I would try it. I will probably put it back to wr timing, just to feel the difference again.
Maybe I will run both set-ups on the dyno just to sate my curiosity.
 

Jonny426

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#9
WR timing/exhaust

MWIESEN thanks for the input. I've been leaning to the Vortip,but the Baja piece looks good also. I'd like to hear from a user of one for their feelings. SFO if you have a dyno at your disposal I seriously want a copy of HP and Torque curves if you do the cam timing differences. Does any one have an address for Yamaha technical? A cam change of 4deg. usually makes a noticable difference in power output,even if it's a lobe separation change. 1 tooth on a cam sprocket has got to be 12-14deg. Has anybody degreed this change or am I going to be the only guy sick (read anal) enough to do it? I will take the time if you guys want to know. Jonny 426
 
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#10
Re: WR timing/exhaust

Originally posted by Jonny426
1 tooth on a cam sprocket has got to be 12-14deg. Has anybody degreed this change or am I going to be the only guy sick (read anal) enough to do it? I will take the time if you guys want to know. Jonny 426
The change retards the exhaust 11.25 CAM degrees or 22.5 CRANK degrees. It's a good mod IF you uncork the exhaust and rejet, if you don't then the mod has limited value at best.
 

SFO

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#11
Ok, Rich, you got me with the jetting...
Is there an alternate needle that will perk the 01 wr up?
I'll try anything once...
What is the set-up?
I remember the thumper talk guys were removing/disabling the acceleraor pumps...
It seemed a bit extreem.

By uncorcorking the exhaust do you mean replacement or just removing the plug out of the end?
You have peaked my curiousity again...