06 WR450 engine Wide-Ratio VS 04 YFZ450 Engine ratio?

I just bought a brand new 2006 WR450 engine and I need to find out what the gear ratios are from 1st to 5th. Does anyone know? I bought the motor for my 04YFZ450 and thought since I am using the bike motor I need some numbers for gearing. I want to know what sprockets to run for woods and sometimes roads. What is the HP and torque stock on the WR on a dyno or maybe at the crank?

Here are the 4wheeler YFZ450 gearing ( I have no idea what it means).

1st: 2.418, 2nd: 1.928, 3rd: 1.562,

4th: 1.277, 5th: 1.050

The quad has a 14 tooth front and 39 tooth rear and 20" tires. If there was only a calcualtor for this stuff.

Sorry for posting in the Bike section but who else better to ask? Thanks, Jeff

You will find the gear ratios in the manual - but dont worry about it.

Most woods riders will put a 13 on the contershaft, STD is 14 and STD rear I think is 50 or 48 (mine has 50). 14 into 50 is around 3.5 so one tooth on the front is roughly 3.5 on the back - if you get what i mean!! If you want more speed for the road get a 48 rear to go with the 14.

Note: a 13 on front will cause more chain rub at the swingarm point but this is minor issue.

In short. [from lower to higher] all with 18 in rim and STD size rear tyre:

13/50 for woods or tight trails

13/48 for less tight trails

14/50 for more open trails

14/48 for wider open spaces

Anyone tried these and like to help out??

BTW Rethall have a chart to check final drive ratios but I am using my daughters computer and dont have the link handy. :excuseme:

Check final drive ratios here:


Yeah, OneToGo, pretty much spot on!

14/50 is stock, and great compromise for everything. I can see why it is stock!

I tried 15/50, only good for keeping revs down on road, and really fast stuff. You can kiss pick up good bye.

I love 14/48, suits me just right. It is smack bang in between 14/50 and 15/50.

Still have great pick up, but not smashing through the gears also. I don't really go for that imaginary 6th gear that I always went for with 14/50. Still wish it had one though.......

I still don't know why you would go to a 13 front. Just leave it in one gear and use the grunt!

As for stock power, about ~45hp from what dyno charts I have seen.

I just installed a 15 on the front. I never got around to counting what was on it, but just assumed it was the stock 14. Well when I counted the original one it was a 13. So I went from 13 to 15, installed the JD kit and Pumped some VP Red 105 in the tank. I havent had it in the trails yet, but about flipped over back wards on the dike behind the house :bonk:

With the ratio at 13/50, first gear was useless. Never used it. Now with the 15/50, first gear is dangerous, and I seem to like it now. And I do ride really tight, steep trails, but that 13/50 was like granny gear :excuseme:

I dont thin kim getting a manual with the motor cause I bought it by itself. The motor is going in the ATV YFZ450. I wont be able to use the gearing fot the WR bike. I appreciate your guys input but I dont know anything about ratios unfortunately. The stock gearing on the quad is 14 tooth front 39 rear and 20 inch tires. but now the old motor has close ratio and i sold the bottom end already and tthe wr motor has wide ratio.

Does anyone know the exact gear specifications in the tranny?

Thanks, jeff

Here are the trans ratios for the 03 WR450:

1st - 2.416

2nd - 1.733

3rd - 1.312

4th - 1.050

5th - 0.840

What they mean is how many times the countershaft sprocket will turn for each rev of the engine. They're obviously a little higher on top than the YFZ, so you'll want to gear a little lower so you can still pull in 5th. You'll probably need around 14/40 or 15/44.

What you need to do is look at the distance the rear wheel travels in each application. The stock 110/100x18 rolls 83.71 inches per revolution (C=3.14*D). Your 20" tire rolls 62.8" per revolution.

Then you need to look at your drive ratio. The stock 14/50 results in .28 revolutions of the rear wheel for every revolution of the countershaft. Multiply that .28 by the distance the wheel travels every revolution (of the wheel), and you will find how far the wheel travels per revolution of the countershaft, 23.44" for the WR and 17.58" for the YFZ, both with 14/50 gearing. That's a lot lower, so what you want to do is find a final drive ratio that is just a bit lower than the WR (remember, we need to compensate for the extra weight). Plug a 14/40 or a 15/45 into the equation and you'll end up with somewhere between 20" and 21" of travel per countershaft rev. Now you can use this new 14/40 ratio as a guideline for changes up or down. :excuseme:

So I should only go up 1 tooth in the rear sprocket? That doesnt seem that much. First gear seems like both the ratios are almost the same but after that the WR is geared higher i think. Do you think I should go a couple teeth in the rear or will that be too much. I do like top speeds cause we drive alot of roads to get to the trails from where we live in the Country.

The only gears I have here are a 14 tooth or 15 tooth front and 2 of the 39 tooth rear sprockets. I used to drive the 4wheeler with a 22 inch tire and it hit 78MPH on GPS and sort of the same with the 20 inch tire with a 1 tooth more up front. As long as I have the 1st gear power maybe ill be fine. When I go to the fairs around town I would like to drag here in NY. if the normal top speed of my YFZ450 is 76MPH with a 20" tire, 14tooth front and 39 rear what will it be with the WR motor and same gearing?

If I knew math I would try to figue it out. Thanks for the help though. Jeff

Sorry True450 - I missed the 4 wheel stuff...saw Y Z and went with that!

Other Quad guys will give you some good advice.

Enjoy :excuseme:

Unfortunately the quad guys dont know anything about the WR motor. So I stuck in with the WR450 bike guys. Whatever I do as far as mods I have to come here, and same with gearing. I dont know anyone or even heard or a WR in a yfz450. The gearing is gonna be different for sure. I just found out a gentleman put a YZ450 engine in a YFZ and had some modifications to make. I just hope the WR is different. As for gearing I will figure it out since I am getting a 24 tooth off the wr450 motor and I found a 13 tooth laying around. We will see how the motor goes in and how it rides. I think I will have some technical issues with the motor if its different mounts.

Can anyone confirm the mounts are the same as a YZ450 with a WR450 motor? The I can see if I can bolt it in. Thanks, Jeff

Mounts for the 450 (03 on?) are the same for YZ: 03 to 05 = WR: 03 to 06.

The YZ switched motor layout for the alloy frame in 06, the WR followed suit for the 07WR. Your 06WR motor will fit in like a glove....

Let us know how you get on with the gearing.

I reckon you will be right with the STANDARD gearing that you had for the previous motor. Maybe drop the countershaft down one tooth as the WR ratios are wider - though I dont have the ratios to check.

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