WR Wide Ratio Tranny in a YZF

... seems like there isn't a lot of difference in the upper gears ...

Are you sure you read the last post correctly?

Are you sure you read the last post correctly?

Well, compared to having to go to 12/61 to get the WR 1st ratio on a YZ, going to 14/47 isn't that big of a jump to get to where you'd have WR 5th ratio on a YZ. This bike is plenty fast enough as is, what I need is some more low speed tractor-ness which is why I was thinking the WR 1st and 2nd gears would be the ticket.

It's not as different as the low gear is, certainly. I just wanted to be sure you hadn't read it as 13/47 instead of 14/47.

It's not as different as the low gear is, certainly. I just wanted to be sure you hadn't read it as 13/47 instead of 14/47.

:thumbsup: Damn if I didn't miss that part twice...

I could look for this info, but I'm sure you already have it some place so I'll just ask- gear ratios for an 00 426 vs. 06 YZ 450F vs. 07 WR 450F?

:thumbsup: Damn if I didn't miss that part twice...

I could look for this info, but I'm sure you already have it some place so I'll just ask- gear ratios for an 00 426 vs. 06 YZ 450F vs. 07 WR 450F?

Gen 2 WR 450 ('07+):

2.636

1.733

1.312

1.050

0.840

Gen 2 YZ450 ('06+)

1.929

1.533

1.278

1.091

0.952

YZ426:

1.846

1.533

1.278

1.091

0.952

Note that the 426 has a primary reduction ratio of 2.952:1. The '05 and later 450's had a "higher" 2.626:1 ratio, about the same as going one tooth larger on the front sprocket.

So the big changes between Gen2 YZ and WR are 1st, 2nd, and 5th with a slight difference in 3rd and very little in 4th, and the 06 450 vs 00 426 is nearly identical save for 1st gear lower on the 450 and the different primary reduction.

So... how does primary reduction ratio affect gearing? You said that the higher PRR on the 450 makes it feel like its geared a tooth bigger up front. IOW, the stock gearing of 13/49 on the 06 feels like the stock 14/49 of the 426?

So... how does primary reduction ratio affect gearing? You said that the higher PRR on the 450 makes it feel like its geared a tooth bigger up front. IOW, the stock gearing of 13/49 on the 06 feels like the stock 14/49 of the 426?

Exactly. The primary reason (pun accidental) was to reduce the load on the clutch so that lighter springs could be used to reduce the lever pull.
Exactly. The primary reason (pun accidental) was to reduce the load on the clutch so that lighter springs could be used to reduce the lever pull.

Gray- thanks for your help... I think now I know what the problem is! I wasn't aware/didn't understand the primary reduction concept, so I figured that my 06 geared at 13/49 was right in between my stock 426 at 14/49 (which always flamed out and stalled on me coincidentally) and the 13/52 gearing I ended up with on that bike. This whole time I've been thinking I have clutch problems when it's just geared to dang high to do me any good!

Now the real question is... will my X-ring chain stretch around 13/52 gears okay or am I gonna have to order a new chain again?

If you have 3/4" of axle slot, it may work. You'll have to try it.

If you have 3/4" of axle slot, it may work. You'll have to try it.

I like to run my rear wheel as far back as possible so I may have added a few links when I installed the chain... can't remember now. I'll hope for the best :thumbsup:

Gray- is the primary reduction on the WR same as the YZ?

Year-to-year, yes.

Year-to-year, yes.

Thanks again! :thumbsup:

I will be performing the WR tranny upgrade in the next few weeks (ordering the parts on Monday). After it's done I'll report back to the group on how it turns out and what the differences yield.

Gray - Do you think there any missing tranny part numbers in the sticky? I'm going to go through the rest of top and bottom end when I'm in there but want to make sure I have what I need from a tranmission perspective.

Thanks for evereybody's help.

Thanks,

David

Gray - Do you think there any missing tranny part numbers in the sticky?

The sticky lists the minimum parts needed, the WR gears. Everything else in the trans that would or could be needed is listed in the YZ450 parts book. If you look it over, you'll see an assortment of small thrust washers and lock rings, all of which can be reused if they are in good condition*, and are the same parts in either trans.

http://www.yamaha-motor.com/sport/parts/home.aspx

*"By the book", the standard procedure is to always replace all snap rings in any assembly that uses them. If they are handled carefully, this isn't strictly necessary.

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