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Discussion Starter · #1 ·
I am trying to change the sprockets and chain on my 2008 ZX-6R, and have run into a snag very early: I cannot get the countershaft sprocket nut to loosen.

Per the service manual, that nut is supposed to be put on with 3 specific requirements:

1. The threads of the nut, and of the transmission output shaft, are supposed to be cleaned and pre-coated with anti-seize compound before installing the nut

2. The nut is supposed to be tightened to 92 ft lb (crazy, since the rotation of the shaft is counterclockwise, so would TIGHTEN the nut, not loosen it

3. There is a large washer behind the nut which is to be replaced each time a sprocket is installed (or re-installed), and then two of its leaves are to be folded up against the sides of the nut to provide another deterrent to the nut unthreading.

Well, I was able to flatten the washer no problem. But when I put the 27mm socket onto a 24" bar, and tried to unthread the nut, no success at ALL. I had the rear wheel properly "blocked" against rotation with a piece of cloth-wrapped 2 x 3 wood, and I sat on the bike and applied the rear brake as well, while pulling the end of the bar counterclockwise. The nut would not move. I tried a very brief application of my electric impact gun (because I don't think using an impact gun on on something fastened to a transmission shaft is a good thing), but it instantly ratcheted instead of breaking the nut loose, indicating (I think) that the nut was tighter than the impact gun's output torque could handle anyway. I also tried pulling the bar clockwise first to see if I could break the seal, but again no movement whatsoever.

In figure that whoever last did a sprocket change there failed to use anti-seize, and/or worse, used an impact gun to tighten the nut far beyond the 92 ft lb spec. Either one, or both, could have created this issue.

When I described this to 2 of my local friends, they both suggested spraying in some penetrating oil, waiting for a full day, and then trying again.

One of the friends suggested putting a 3 or 4 foot pipe over the bar, to get more leverage, and he thought that might be gentler than going at it with a stronger impact gun (at a local auto repair shop?), as the extended bar will not generate any shocks back to the transmission, which could cause internal damage.

The same friend also said to NOT use a heat gun on the nut, as that could potentially damage a transmission output seal.

Any experienced suggestions?

Any specific penetrating oil suggestions?

Jim G
 

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I am trying to change the sprockets and chain on my 2008 ZX-6R, and have run into a snag very early: I cannot get the countershaft sprocket nut to loosen.

Per the service manual, that nut is supposed to be put on with 3 specific requirements:

1. The threads of the nut, and of the transmission output shaft, are supposed to be cleaned and pre-coated with anti-seize compound before installing the nut

2. The nut is supposed to be tightened to 92 ft lb (crazy, since the rotation of the shaft is counterclockwise, so would TIGHTEN the nut, not loosen it

3. There is a large washer behind the nut which is to be replaced each time a sprocket is installed (or re-installed), and then two of its leaves are to be folded up against the sides of the nut to provide another deterrent to the nut unthreading.

Well, I was able to flatten the washer no problem. But when I put the 27mm socket onto a 24" bar, and tried to unthread the nut, no success at ALL. I had the rear wheel properly "blocked" against rotation with a piece of cloth-wrapped 2 x 3 wood, and I sat on the bike and applied the rear brake as well, while pulling the end of the bar counterclockwise. The nut would not move. I tried a very brief application of my electric impact gun (because I don't think using an impact gun on on something fastened to a transmission shaft is a good thing), but it instantly ratcheted instead of breaking the nut loose, indicating (I think) that the nut was tighter than the impact gun's output torque could handle anyway. I also tried pulling the bar clockwise first to see if I could break the seal, but again no movement whatsoever.

In figure that whoever last did a sprocket change there failed to use anti-seize, and/or worse, used an impact gun to tighten the nut far beyond the 92 ft lb spec. Either one, or both, could have created this issue.

When I described this to 2 of my local friends, they both suggested spraying in some penetrating oil, waiting for a full day, and then trying again.

One of the friends suggested putting a 3 or 4 foot pipe over the bar, to get more leverage, and he thought that might be gentler than going at it with a stronger impact gun (at a local auto repair shop?), as the extended bar will not generate any shocks back to the transmission, which could cause internal damage.

The same friend also said to NOT use a heat gun on the nut, as that could potentially damage a transmission output seal.

Any experienced suggestions?

Any specific penetrating oil suggestions?

Jim G
I just put a 2x4 in the back rim (wrapped in rags) and use a Milwaukee cordless impact works every time
 

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Discussion Starter · #3 ·
I just put a 2x4 in the back rim (wrapped in rags) and use a Milwaukee cordless impact works every time
Thanks for the reply. I did use the cloth-wrapped wood trick. My electric impact wrench did not do the job, nor did a 4 foot breaker bar. I ultimately had to buy a 650 ft lb pneumatic impact wrench, and alternate the use of that impact gun with the 4 foot breaker bar, and finally got the nut off.

But now, I am waiting for a week for a new sprocket nut, because people before me had evidently had the same problem, and their cumulative efforts had put a number of dings in both the 27mm and 32mm hexes on that nut (They had also not used anti-seize when INSTALLING the nut), and I figured if I used it one more time, I might not be able to get it off at all the next time.

I am torn on whether I should follow the service manual instructions to torque to 94 ft lb and have this epic struggle the next time I want to change the front sprocket, or whether i should just torque to a more modest torque, like maybe 75 ft lb to make future removal easier. After all, the primary "Load" on the sprocket is carried by the SPLINES on the sprocket and the tranny output shaft, AND under acceleration, when the forces are the highest, those forces will tend to TIGHTEN the nut, AND the bent tabs on the SPLINED washer behind the nut prevent any nut rotation anyway.

But I am also told that countershaft sprockets DO sometimes loosen and actually fall off sometimes (Not commonly).

So not sure what to do.

Jim G
 

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I'm too late to this thread as far as removal goes, but I've always used an impact if my first attempt at removal with a breaker bar is unsuccessful.

I would torque it to spec. There are a gazillion posts about seized countershaft sprocket nuts. They always take quite a bit of torque to remove, but it will be MUCH easier with anti seize on it.
 

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I'm too late to this thread as far as removal goes, but I've always used an impact if my first attempt at removal with a breaker bar is unsuccessful.

I would torque it to spec. There are a gazillion posts about seized countershaft sprocket nuts. They always take quite a bit of torque to remove, but it will be MUCH easier with anti seize on it.
This is what I use it’s pricey but powerful
Font Screenshot Parallel Rectangle Number
 

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Fingers crossed the Output Shaft Bearing didn't get damaged when you applied that much side ways force.
I NEVER have had to use a Bar to remove a Sprocket Nut, Always my Trusty Snap On Impact Gun.
 

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Discussion Starter · #7 ·
Fingers crossed the Output Shaft Bearing didn't get damaged when you applied that much side ways force.
I NEVER have had to use a Bar to remove a Sprocket Nut, Always my Trusty Snap On Impact Gun.
No. The impact gun is actually much harder on the chain, sprockets, tranny shaft, and everything attached to the tranny shaft than a breaker bar is, because:

- It applies MUCH greater torque than the breaker bar does, because you can control the torque applied to the breaker bar to "just what is needed" to break the sprocket nut loose, whereas you cannot control the torque applied by the impact gun. The impact gun was supposedly applying 650 ft lb of torque. No way that I could apply 650 ft lb via the breaker bar

- The impact gun by definition "impacts" all the affected parts, whereas the breaker bar just applies a steady force. Impacts are FAR more destructive than steady force.

And, interestingly, I was applying the impact gun and the breaker bar alternately, and it was the breaker bar, not the impact gun, that ultimately broke the nut loose.

Jim G
 

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I would usually agree with Kev on Snap-on air impact gun, 3/8", then escalate to 1/2" for stubborn ones. But I think Jim makes a good point about caution using impact power. One day in the shop, I applied air impact force to a sprocket nut on a fairly nice Suzuki bike, low mileage well-kept, just needed new chain and sprockets. I was surprised, and everyone in the shop shocked (especially the owner) when the countershaft snapped right behind the sprocket, ouch! Customer wasn't too happy either, and a few weeks later, I wasted an entire flat rate day installing a new countershaft and seals and gaskets, for no pay. Lesson learned. So, I think the cautious alternating between breaker bar and air power might be the answer. I also flood the area with Zepreserve loosening fluid, it really seeps in there.
 

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For what it's worth, when I use an impact on mine, I put the transmission in neutral. That way the only stresses are on the chain, sprockets, and wheel spoke/swingarm.
 

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Check out this solution to a related problem, weak or cross-threaded countershaft threads:

Automotive tire Rim Auto part Motor vehicle Bicycle part


Would you believe the chain and sprocket are practically new!
Yep, it's welded, how rude is that! Lining up replacement countershaft, etc...
 

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Discussion Starter · #14 ·
For what it's worth, when I use an impact on mine, I put the transmission in neutral. That way the only stresses are on the chain, sprockets, and wheel spoke/swingarm.
Yes, that is what I did. And, if course, it was the OLD chain and the OLD sprockets that took the impacts, and the effects of the 4 foot breaker bar, not the new ones.

Jim G
 

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Mine has always been a pain to remove. I use a 2 ft breaker bar with the handle from my aluminum racing jack over the end of it. Gives me a bit over 6 feet of leverage and it STILL takes most of my weight to break it loose while also having to lock down the chain and rear wheel.
 

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Discussion Starter · #16 ·
Mine has always been a pain to remove. I use a 2 ft breaker bar with the handle from my aluminum racing jack over the end of it. Gives me a bit over 6 feet of leverage and it STILL takes most of my weight to break it loose while also having to lock down the chain and rear wheel.
Which method did you use to put it ON: torque wrench or impact wrench?

Jim G
 
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