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TeamScream

Real Differences tween 2001 YZ and WR ?

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I have a 2001 WR426F that has been in supermoto trim since the day I bought it new in late 2000, it has been a wonderful machine.

3 years ago I did a 444 big bore kit to it, had the head cleaned up and ported slightly and it was a definite improvement.

Like all of the after market pistons this Weisco started to rattle around in the bore after a few thousand miles, and I am sure the rod is a little long in the tooth.

Long story short, I was debating rebuilding this WR motor from the ground up when I came across a brand new YZ426 motor in a crate complete with carb, so I bought it, but now I am having second thoughts.

My question(s),

How much different is the YZ gearing than the WR (same year engine)?

Were there any other differences in the 2 engines besides cam timing and throttle stop?

I will need to keep the lighting coil because my bike is street legal so I have lights and signals, do I just swap the lighting coil from the WR motor over to the YZ motor? is there anything else I need to do electrically to do that right?

Also I read allot about counter balancer woodruff keys back in the day, I can say however that my WR motor never had an issue with that, so is there a hardened (harder than stock) woodruff key that I should consider replacing before I put the motor in the bike?

I guess my main fear is that with the YZ gearing I may not like it as much on the street, so I need some input on that from those of you with experience.

I have not committed to anything yet other than the fact that I have a brand new YZ engine in a crate with Japanese writing all over it sitting in my garage, I will not be putting the big bore kit on either of these 2 engines this time around as I really don't think the reliability is there with after market pistons and the extra bottom end that I got out of it was really not worth the piston slap noises I had to put up with after about 6 months of weekend riding.

So the bottom line is this, if you had the choices I have now of (1) installing a brand new engine including swapping the ported head from the old engine, swapping the lighting coil from the old engine and calling it a day or (2) rebuilding the old engine which I am sure will require all new lower end bearings, a few gears, shift forks, clutch basket and clutch, crank work most likely (Falicon), with a knife edge rod etc.

I am certain I can sell this crated engine to a kart guy on ebay and not lose a dime, I paid $1400.00 for it.

I guess the other thing I could do is sell the old engine on ebay for close to a grand and end up paying $400.00 for a brand new engine which would not be all that bad.

Thoughts? suggestions?

Thanks.

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It you pull the gray wire and change the cam timing on a WR you basically have a YZ with different forks that runs up to 83MPH.

Am I incorrect?

A bitchin bike is a '01 YZ426 with 1st and 5th gears out of a WR. :banghead:

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I think the YZ has a close ratio transmission vs the wide ratio WR.

lol, really? :banghead:

I knew that, but not having had the chance to ride a YZ to compare I was looking for a more descriptive comparison of how the bike runs through the gears, does the YZ have more speed in first gear or does the WR have more speed in first gear with the same front and rear sprockets installed on both machines?

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lol, really? :banghead:

I knew that, but not having had the chance to ride a YZ to compare I was looking for a more descriptive comparison of how the bike runs through the gears, does the YZ have more speed in first gear or does the WR have more speed in first gear with the same front and rear sprockets installed on both machines?

YZ is taller in 1st.

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I own an '02 WR426 supermoto, and have ridden a couple of YZ426 supermotos on the road.

I find first is useless on the WR, as i shift straight through it, but on the YZ's it's a lot of clutch and revs to get it going, as they have to be geared so tall to get a decent speed out of them in top because of the shorter 5th gear on the YZ.

The increase in gearing effectively spaces the gears further apart too. The WR box is infinitely better in every way for road use.

Personally I'd rebuild the WR, and sell the YZ lump, or maybe even get WR gears installed in the fresh YZ motor.

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The YZ carb is almost the same but is has not air cut valve, EJP needle instead of the DQR, #100 paj instead of the #75 for the WR, 72 starter jet whereas the wr has a 65. 162 mj instead of the 165 for the wr... that is probably so to suit the difference in timing and because there is less restrictions with regard to noise and pollution with the YZ.

I feel the YZ timing makes my WR engine more responsive but you'll loose that feeling if you gear a yz up so that it can reach high speeds. That's what I feel from gearing up my WR for the street.

My WR has a 18" rear wheel for the street and it is geared 16-44. The first speed feels quite long with this gearing and the 4th has to be pushed to reach the 5th with enough rpm. Next time, I'll ride a 15 t up front. I bet 15-44 would be a blast with a 17" rear wheel.

From my little experience, I'd stay with the WR transmission, YZ time the engine and jet it properly. You'll have about the best ou can find I'd say.

Good luck

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16-44???

Normally use 13-42 or 14-42 when my bike's in supermoto trim.

Before i bought it, the friend who owned it previously took it drag racing and did a 12.5 @ 109 on 15-42 gearing, although it ran out of revs in top just after 300 yards.

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15-42... 16-44... almost the same thing...

12.5 @ 109 on 15-42 gearing? You mean on a 1/4 mile race? Oh man! :banghead: That's faster than any muscle car I've been trying! 109 miles per hour on a 426? I did not know they could go so fast! What's the bike boosted with? Cams? Higher compression?... tell me. How much HP does the bike show at the rear wheel?

Thanks

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16-44???

Normally use 13-42 or 14-42 when my bike's in supermoto trim.

Before i bought it, the friend who owned it previously took it drag racing and did a 12.5 @ 109 on 15-42 gearing, although it ran out of revs in top just after 300 yards.

I find that top speed hard to believe. :banghead: 26 MPH faster top end then my stock geared WR?

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That's a quarter mile time at a run what ya brung.

2002 WR426F Supermoto

Skimmed and flowed head,

Full acrapovic Ti exhaust system

53 rwhp

On the day, i was riding my TL1000S, which was did 11.26@129

The WR, with a friend of mine riding it, did 12.50@109 it's all about getting off the line. The WR outdrags most sportsbikes for the first 100 yards because it's so light. The guy riding it weighed 11 stone too (about 155 lbs).

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I find that top speed hard to believe. :banghead: 26 MPH faster top end then my stock geared WR?

I'll see if i can get the timecard.

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lol, really? :banghead:

I knew that, but not having had the chance to ride a YZ to compare I was looking for a more descriptive comparison of how the bike runs through the gears, does the YZ have more speed in first gear or does the WR have more speed in first gear with the same front and rear sprockets installed on both machines?

Wide ratio= larger gear spread, thus a deeper 1st gear and a taller 5th gear, therefore, now listen closely, your speeds will be different in 1st and 5th given the same sprockets. :banghead:

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Wide ratio= larger gear spread, thus a deeper 1st gear and a taller 5th gear, therefore, now listen closely, your speeds will be different in 1st and 5th given the same sprockets. :banghead:

No sh-it sherlock, but you still did not answer the question.

Simply stating that "the speeds will be different in 1st and 5th" falls short.

It is obvious that the 1st and 5th gears are "different".

My question was a bit more specific and I asked for a bit more specific answer. However.....I have now discovered by reading a bunch of other posts that the WR 1st is more like a "granny" gear and that the 5th gear in the WR amounts to more top speed (MPH) than the YZ 5th gear provided the same final drive sprockets are used on both bikes.

I only asked the question(s) because I have not had a chance to ride a YZ and compare notes, and I now have a brand new YZ engine in a crate and my original WR engine that needs to be rebuilt.

But thank you for taking the time to read and attempt an answer.

The opportunity was there for me to replace the WR engine with the brand new YZ engine but the disparity in gear ratios would not be the best option for me as my street legal WR is in full supermoto trim (with YZ tank and plastics) and I need the taller (WR) gearing for street speeds.

It just doesn't make a lot of sense for me to take a brand new engine and tear it apart to replace the 1st and 5th gears with WR gearing.

So, where that leaves me now is I am going ahead with a complete rebuild of the WR engine, Falicon "supercrank" and knife rod service and I will sell this brand new YZ engine and try to break even on it.

Thanks to everyone who took time to reply to this post......

I was in a bit of mind freak because I just spent a bunch of money on a brand new crated engine only to realize I should have done more research before I bought the thing, I was just so stoked to find a complete engine, brand new in a crate from the factory in Japan that I jumped on it before the opportunity went away, then got really disappointed when I realized it was NOT the best option for my application.

Sometimes is is comforting to post in the place that I have come to call home for the last 4 or 5 years and get some feedback from the brethren.

Scream.

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Scream,

As per my previous post, the WR 5th gear is a godsend on the road in comparison to the YZ's short 5th.

You're doing the right thing re-building the WR. :banghead:

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Thanks GLM,

I appreciate your help bro.

It also comes down to more than that, when I think about it I would have to swap out the lighting coil and the mods I did to it to make it charge a battery and all that.

Plus the WR engine will not need every single part replaced, definately all the bearings on the lower end for good measure, but most if not all of the gears should be in great shape still.

It is mainly the crank and rod + bearings that I am going to replace/rebuild for safety sake.

I just wish that the big bore concepts were a little more sound.

For some reason the guys that make big power I associate with say that the after market pistons are just not up to snuff.

Makes me think that a 450 piston might me a good thought to get a little more displacement.

I am going to research the differences in piston pin height and diameter.

Thanks again brother,

Scream

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No worries mate.

For what it's worth, the guy who used to own my WR was a total loon. The bike used to get a full engine and gearbox rebuild every christmas at a local firm that build some of the fastest Yammies in the country for MX use.

They always used genuine Yamaha pistons in their bikes, because they lasted better.

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lol, really? :banghead:

does the YZ have more speed in first gear or does the WR have more speed in first gear with the same front and rear sprockets installed on both machines?

So this wasn't one of your questions? :banghead:

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I'll see if i can get the timecard.

I would love it. Awesome if a fact!! :banghead:

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Found the post on another forum i'm on.

I was wrong. it was actually 12.5 @ 106mph

http://www.visordown.com/forums/showthread.php?t=190653

If he's got the timecard still, i'll get it next time i see him.

It was impressive to watch, as it was slaughtering all the other supermotos in our group over the 1/4. There were a couple of KTM supercomps, a CRF450R, and a KTM 660 as far as i remember. - They all became WR fodder.

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