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WR250R gearing

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I just got a WR250R from a friend (thanks Eric!). He put a 12T on the front. I've read on the many (many!!) posts about this stuff that the 12T adds a lot of vibration. Why?

I'm thinking of putting either a 45 or a 47 on the rear. Would I notice much difference with a 45? Would the 47 make the 1st gear almost unusable unless it was a really steep trail or especially hard technical trail requiring slow grunting along?

I am fine with a top speed of 60 or 65 on the highway. If I go to a 12/47 would I lose that capability (I haven't tried any of the calculators to figure that out yet)?

Steel or aluminum? I know steel will probably last longer and isn't necessarily heavier, depending on the brand selected. But if I can get a year or 1,500 miles out of a $60 rear sprocket then I don't consider that too bad - I can live with that.

Thanks. I'm sure as I get into this new adventure I will have more questions.

Larry

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I ran 12/47 sprockets on my 2008 WR-250R for thousands of miles.

I felt it was very good for splitting trail riding and street riding.

The gearing was much better for trail use than the tall stock ratio, and the bike would still hit 80 mph, which I felt was plenty fast for a 250cc single-cylindered bike on the street.

I could easily cruise at 65 mph and have some left in reserve, so don't sweat it.

I never experienced any vibration because of a 12-tooth sprocket.

I like Sunstar steel sprockets because they have a fair bit of material removed where it can be done without weakening the sprocket.

Some steel sprockets (like JT) are basically a chunk of steel which are very heavy in comparison.

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I also use a Sunstar. They are the OEM makers for Yamaha sprockets, at least the steel ones. ( or they were) I'm running the original 13 front, as i don't want to go smaller, too hard on the chain from my point of view. I went to a 47T rear. The WR250F fits, but you have to change the bolts as well. I think my sprocket cost me less than 40 bucks. I expect it will last the chain. I don't care for aluminum sprockets except for competition use where every ounce counts, as they wear too fast. When my current setup wears out, I may go to 14/51 to keep the same ratio, and have a little better life for the chain. I'll see how this does first. So far, it is low enough. I ride the road to the off-road areas, so i need to be able to keep out of the way on fast four lanes. I only have about 3-4 miles of it to run, but dawdling there isn't a great idea, it runs 65-75, trucks and all. The rest is all back country roads at about 45-50. I climb so pretty steep, loose stuff with my setup, so I think it is enough. These things are surprisingly grunty, considering how flat they often feel at the bottom. Obviously, they pull better than they feel.

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Yamaguy55, YZEtc,

Thanks for the info and feedback, very helpful and much appreciated. Now to make the change to a larger rear sprocket! Happy trails guys!

Oh, one other question. Can either of ballpark some numbers for chain life with a 12T versus a 13T? Like 3000 miles on a chain with a 12T and 4000 miles with a 13T? And I assume that most of the extra wear that comes from the smaller front cog is from the high rpm running? Is the extra wear just due to the fact that the fewer teeth are hitting the chain more (more times) than the teeth on a larger cog? Just guessing- haven't really investigated the physics behind that issue.

Thanks!

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I got 7,000 miles out of the original 13t sprocket, put a 12t on and got about 5,000 (a little less since the odo is now off a bit). Currently using 13/48 and next time I may go 13/50.

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The 12 tooth gear will wear on the underside of your swingarm. Go larger rear sprocket.

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The 13T will, too, if you let the chain get too loose. Learned that the hard way.

Sarah

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The 13T will, too, if you let the chain get too loose. Learned that the hard way.

Sarah

But at least it gives you fair warning: you can hear the chain slapping the swingarm and the chain guide before it starts eating anything. Unless you're numb and deaf......:smirk:

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It was sneakier than that actually, happened in the midst of a 200+ mile ride. There have been a few of us caught that way. I've learned from it, I hope.

Sarah

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When I got my WRR (estate sale) the chain was making quite a racket even though it only had 260 miles on it. I dug out the manual and found it quite loose. There has also been a bulletin about chain adjusting on thses from Yamaha, dated 12-15-08 number M2008-020. Says: 165mm in front of front bolt for chain guide, clearance should be 8 to 13mm. They also suggest use of a tension gauge, but I don't go that far.

One last thing: I have replaced both of my rollers with aftermarket sealed ball bearing versions, which to me are not only more durable but quieter. After the stickers get some wear on then, they get clattery. Sometimes, they get to where they don't even roll. Years ago, I had chain life problems with an open class YZ, and some of it was from the stock chain rollers not rolling. The power to weight ratio didn't help either.

By the way: I'm partially deaf, and often numb.

Edited by Yamaguy55
More info

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It was sneakier than that actually, happened in the midst of a 200+ mile ride. There have been a few of us caught that way. I've learned from it, I hope.

Sarah

Ok: you got me; I inspect my bike before and after each ride, as I don't like unpleasant surprises. I generally look at everything, but not at anything in particular. So after the above statement about chains and swing arms, I just went out to the garage and can't see where it could hit. I have to ask: where did it get yours? I have the large rubber/plastic swing arm protector at the front which covers both top and bottom, and the guide at the rear on the bottom. What's left?

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The following link shows a pic of what the talk is about with WR-250Rs and WR-250Xs and swingarm sliders.

See how the chain has sawed through the slider and into the metal of the swingarm.

Also notice the angle at which the swingarm sawing is at - where the rear suspension is fairly compressed.

Myself, I find this kind of wear hard to believe that it's from a too-loose chain merely slapping against it.

To me, it appears that the chain was forced to grind through it while under tension.

http://img7.imageshack.us/img7/8225/sprocket4.jpg

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My slider was eaten away at the front (exactly as YZ's pic shows) and my swingarm had just the beginnings of a couple of shiny marks. I was heading home from a day ride and suddenly noticed lurching under acceleration; I hadn't had the Safari tank long and first thought it must be some type of fuel delivery problem. I geared down and goosed it and realized immediately it was the "chain skipping" I'd read about. Once I got pulled over I saw the chain was obviously too loose. I stood there staring at the bike feeling fairly stumped; I think I had about 8,000 miles on the bike at the time and I'd always watched the chain pretty close. Anyway, got out my tools, tightened the chain and rode the 100 or so miles in with no problem. Nearly croaked when I got home and checked the slider and swingarm.

Some folks swear it's due to a 12T sprocket but mine was a stock 13. Some folks say it's from a tight chain but mine was obviously too loose. And some folks don't believe in chain skipping but I can tell you something funky sure nuff happens when the factory chain gets too loose on those factory sprockets.

???

Sarah

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I just took another look, my lower guide has obviously been "kissed" by the chain, but no more. I have the front sprocket cover on mine replaced with the Zeta version, because I had problems with leaves and sticks packing in there. I'm wondering if the change of chain guide rollers has changed my geometry. And what the results will be. I'll have to keep an eye on this.....wasn't aware of it at all. I have a lowering link and that certainly will change the relationship of the chain to the swingarm. Did all of those with problem bikes have lowering links? The reason I ask is the lower run on the guard would be hit more often with a link than with the stock setup. Stock, the top would take most of the beating.

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I don't mean to jack this thread , but ...

One last thing: I have replaced both of my rollers with aftermarket sealed ball bearing versions,

I have intentions of doing the same on my XT350 project . Do you see any downside ?

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I don't mean to jack this thread , but ...

I have intentions of doing the same on my XT350 project . Do you see any downside ?

Only in that they come with too little grease. I pop off the seals and pack them with my overabundant supply of waterproof moly based grease, and then put the seals back on. Then I never touch them again until they're ready for replacement.

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My slider was eaten away at the front (exactly as YZ's pic shows) and my swingarm had just the beginnings of a couple of shiny marks. I was heading home from a day ride and suddenly noticed lurching under acceleration; I hadn't had the Safari tank long and first thought it must be some type of fuel delivery problem. I geared down and goosed it and realized immediately it was the "chain skipping" I'd read about. Once I got pulled over I saw the chain was obviously too loose. I stood there staring at the bike feeling fairly stumped; I think I had about 8,000 miles on the bike at the time and I'd always watched the chain pretty close. Anyway, got out my tools, tightened the chain and rode the 100 or so miles in with no problem. Nearly croaked when I got home and checked the slider and swingarm.

Some folks swear it's due to a 12T sprocket but mine was a stock 13. Some folks say it's from a tight chain but mine was obviously too loose. And some folks don't believe in chain skipping but I can tell you something funky sure nuff happens when the factory chain gets too loose on those factory sprockets.

???

Sarah

I think the stock rear with the rubber "sound deadeners" has a tendency to help a looseish chain ride off of the sprocket. the side plates bear pretty hard onto the rubber. I noticed this until I replaced my stock 43 with a Sunstar 47, which doesn't have the rubber. The problem vanished at that point. I agree with you: it does skip, or certainly sounds/feels like it does.

At any rate, using the tension from the bulletin, plus going to a normal sprocket without the rubber side areas, has completely eliminated this.

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