99-07 Renthal Sprockets fit on 08 YZ450F?

I ordered some Renthal sprockets from LocoMX, I have an 08 YZ450F and they sent me 99-07 countershaft and rear sprockets. The rear fits fine, but the countershaft looks different than the stocker and when you tighten it, it becomes almost impossible to rotate. Is the spocket just the wrong design? The stock one has a flat side, and a outward groove. The renthal has semi wide grooves on each side.

Can anyone answer my question?

You have the sprocket mounted with the cool looking undercut side out, don't you? That's what I thought. Turn it around flat side out and everything will be fine. The cut side is made like that so the dust cover can overhang the end of the splines. When you mount it backward, the flat side clamps against the dust sheild and binds it up.

And yes, this is one of those things about which you should not ask how I know.

No greyracer, the stock one was mounted correctly with the flat side out. The renthal has no flat side, but both sides of it are grooved. But not like the stock groove, it is a wider groove and when mounted and torqued it does not want to spin easily at all. It takes much force to turn it. I am going to try and post comparison pics of it.

The left is the stock, right is Renthal. Stock Inner side has groove.


Flat side (outer) stock


If I lightly tighten the Renthal, it will spin normally, start to torque and it gets harder to turn. Need your help on this one, I don't think the 07 sprockets are the same as the 08 are they?

If both sides of the Renthal sprocket look like the side you show in the pictures, then that sprocket won't work. The sprocket has to have one side on which the raised step on the inside is no wider than the one on the inner diameter of the sprocket. The only alternative would be to grind down the extension on the dust shield shorter, but I don't recommend it.

The '99-'07 sprocket is the same as the '08, but the side of the Renthal that you show is wrong for the inside of a YZ450 sprocket.

Those pictures were of both sides of each sprocket. I checked the Renthal website, and the part # is 289-520-13. It was under the lookup for a 2008 Yamaha YZ450F.

I wonder how many people have bought this part and installed it. It does not work on this model of bike, unless you finger tighten it and install the lockwasher. That is not safe and will severely wear out a few components on the bike.

Greyracer, would it be a bad idea to just run that stock front sprocket with the new chain and rear sprocket? I have always heard never run new chains with old sprockets, but the stock one shows little wear.

Your OEM sprocket looks fine. I'd run it. In general, and excluding the extreme cases, chains wear out sprockets, not the other way around. As I say, you can look hard enough and find examples to the contrary, but for the most part, even a noticeably worn sprocket has little means of accelerating the wear on a chain. Very worn sprockets are a different story.

It's different with chains. The pitch of a chain (the distance between pins) increases as it wears, so that it no longer fits over the sprocket with uniform pressure any more, placing the entire drive load on a small number of teeth near the point at which the chain feeds onto or off of the sprocket. With that in mind, be very careful in replacing sprockets without a new chain, more than the other way around.

In the process of replacing my renthals 14/51 on my 07. No issue with my front with over a year on it (289-520-14) Keeping in mind mine is a 14, it does not look the same as the pic above? The channel is much wider on mine more like the stock appearance. I am going to move forward with replacing them with the renthal's and will advise if I have any issues with the new one.

I ended up running the TAG metals front 13T, and the Renthal rear. I have rode it several times since, and had no problems.

Well I read this thread got the same renthal front sprocket derek got and i installed it last night. Before tightning it i compared it and the renthal fits on exactly like the stock one, they stop in the same place washer fits and all. the shield rubs on the inside ridge on the stock one to you can see the mark in his picture the only difference is on the renthal the ridge is a little taller. i torqued it down little by little checking the spin frequently and it spun just like the stock one even after i torqued it all the way.

So my question is, is it ok to run? i dont see a problem myself but i would really like another opinion. thank you.

you should go with the Sunstar 32513 - indestructible. when you need a rear, the Works Triplestar will outlast any other aluminum if you are concerned about life - hard anodizing increases process increases durability over anything else on the market.

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