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Post by vectisitch on Sept 13, 2021 16:49:56 GMT 1
Still learning about my new bike. There is a scratchy screech from the powervalve servo when i turn the key. What can cause that? Can i open it and grease it or is it likely something worn? Also i've taken the pipes off and looked into the exhaust ports. Wit hthe ignition off the powervalves are in the fully open position but are in slightly different positions. I would have thought they would both be flush with the actual port?? One is but the other seems "pushed" further up into the port. This is on a fully rebuilt engine with around 2k miles on it since. Could the valve clamp be worn?
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Post by bare on Sept 13, 2021 16:53:10 GMT 1
Servo Can be easily disassembled and re greased.
Coupler is the part that sync's the two valves.
Fair chance it's messed.
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Post by vectisitch on Sept 13, 2021 16:54:09 GMT 1
Yeh to my mind both valves should be exactly the same position in all settings. Looks like i'll be taking the barrels off then.
Once i take the valves out is it ok to reuse the seals and orings?
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Post by jon on Sept 13, 2021 18:41:47 GMT 1
Sorry to be the bearer of bad news, but it’s common for the valves themselves to wear as well as the coupler.
Simple check and easy removal of the coupler though to see.
Jon
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Post by vectisitch on Sept 14, 2021 15:25:36 GMT 1
both valves are ok at the outer ends but both are worn where the clamp goes, and the clamp is worn too.
Are Norbos billet valves worth buying? Also it looks like the barrels have had some light tuning too. Not too much and the reeds are the standard metal ones. Haven't checked the jetting yet
Is the clamp ok to reuse or is it too worn? The middle clamp seems to be the weakness in the pv system to me. Especially the rubber part. Surely if it's clamped tight with no movement then it can't wear???
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Post by jon on Sept 14, 2021 20:17:22 GMT 1
vectisitch as I said it is quite normal to find this wear on old valves. The billet ones are OK and if that’s all that available these days as the right hand is NLA, then not a lot of choice. Jon
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Post by bare on Sept 14, 2021 22:18:01 GMT 1
A bit of skilled TIG work could restore that valve end. IF the rest of the valve is still good.
Sometimes the bearing surfaces wear badly. But even then a steel re sleeve can be a better than original 'fix.
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Post by vectisitch on Sept 15, 2021 13:19:00 GMT 1
Any reason why yamaha didn't make these valves from steel? They seem a weak link to me made of butter like they are. Norbo is out of stock of the billet ones
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Post by bare on Sept 15, 2021 16:28:34 GMT 1
Steel ? Yama San was incredibly Cheap.
Hell, even a decent grade of Aluminum would have been dramatically better.
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