I'm finally starting to dismantle my NSR to replace the crankshaft. I'm struggling with the powervalve cables. When I try to unscrew them from the bracket on the cylinder, the cables twist and I'm afraid it's going to damage them if I keep turning until they unscrew from the bracket. Is there a better way to remove them? Also, I tried to loosen the nut where the powervalve pivots but the shaft spins and the nut is not coming off. It feels like the entire shaft is stripped or something. When I move the powervalve lever I can feel the valve moving through the exhaut port so I think it's still working. It just seems strange the the pivot shaft turns so freely and the nut won't loosen or come off. Did I screw something up?

Skunkbait.

You're not taking the cables off the bracket, right? There's no need to do that unless something else is wrong.

On the bracket, there's a couple holes that will line up so you can stick a philips screwdriver in and the valve won't turn. Take the nut off first (it's reverse thread which may have had you messed up). Note where the washers go so you can put them back in the correct order. Then take the 2 attaching bolts out (normal thread) and the whole assembly comes off the cylinder.

Usually you don't have to jam the bracket with a screwdriver but if you've been trying to turn the nut the wrong way it might be on super tight now.


Last edited by craigsutton on Mon Apr 12, 2010 12:49 pm; edited 1 time in total

Can you not just remove the mounting brackets from the cylinder?Also the shaft nut is a left hand thread.

craigsutton wrote:
...if you've been trying to turn the nut the wrong way it might be on super tight now.

If you've been trying to unscrew the nut the wrong way (it's a left hand thread, as Craig pointed out), then from what you are describing you have most likely stripped the thread off the end of the RC Valve shaft. They tend to strip before the end shears off!
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I don't think the threads are stripped. It's like the entire shaft is turning. Am I royally screwed?

Do you have a 6 point 10mm wrench? If so use that to see if the shaft is turning while you try to loosen the nut.

the service manual points out clearly that the shaft threads are left handed

if the shaft is "spinning" in the cylinder, then either the shaft or the flapper valves have been damaged.

You would have had to turn the nut pretty hard, as the flapper valves and the shaft are pretty hard steel. My guess is the threads would have gone first.

Thanks for the advice. I hope it's just stripped threads. If I move the powervalve lever (where the cables connect) up and down I can feel the valves moving through the exhaust port so the system seems to be working.

Skunkbait

Sounds like the worst thing that could be wrong is that the threads are gone on the shaft or the nut. Jam a screwdriver in the holes that match up from the lever to the base and use a wrench to try to remove the nut. If it just spins you can pull on it while turning to get it off. Once you have the nut off you'll be able to tell if you need a new nut, shaft, or both.