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Power valve issue?, hopefully, 2013 Beta 300rr

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Went for a trail ride just outside of Taupo central north island of New Zealand yesterday, pumice based so plenty of traction once the ice had defrosted in the morning, so plenty of fun.

Last lap of the day bike started to develop a funny noise and also started to vibrate noticeably more of idle, idling don't notice the sound, seems to be coming from the top end around the power valve area.

Was wondering can can power valve get sticky or if anyone else has had this sort of issue?

Running Castrol TTS fully synthetic @ 55 to 1

Would consider myself a solid trail rider but definitely not able to use engine to its full abilities so not really flogging it, more confident in awkward single trail than wide open fast stuff

 

 

 

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Start by checking engine mounts: front and under the engine, cyl head.

 

PV has nothing to do with vibration. If it sticks closed, the engine won't rev up to the higher rpms, if it sticks open you'll loose all the torwue down low.

Beta's PV is very well built and its almost maintenance-free, however this is related closely with the oil used.

 

Speaking of oil, I stopped using TTS on my DT200R about 25 years ago because of the smoke, the smell and the price.

Your problem should not be oil-related but I would use something more modern.

Perform a good visual check around the engine area.

Edited by dirtbird

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checked all engine mount bolts, all good, and the expansion chamber springs are still there. There is a little bit of oil seeping out but bugger all.

Would having a to big spark plug gap cause detonation? Not sure what 2 stroke detonation sounds like.

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Detonation would only last a few seconds, then there'd be a hole in the piston: not it. Could be plug gap causing funny idle; more likely something else: airboot, muffler to header joint, plug loose, kink in fuel line...

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Pipe orings, especially if pipe was hit and maybe misaligned slightly at flange. Take it apart, clean well, new orings with a coating of red RTV. See if that helps.

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Pipe orings, especially if pipe was hit and maybe misaligned slightly at flange. Take it apart, clean well, new orings with a coating of red RTV. See if that helps.

When i bought the bike it came with a new fmf expansion pipe, so i took the orings of the cat convertor expansion pipe which were unused and put the new fmf pipe on and noise seems to be gone :thumbsup:. Thanks for the help guys, didn't sound like an exhaust leak to me but seems to have been, my first 2 stroke so a few things still to learn and i can stop worrying that its about to grenade. Loving the 300 2 stroke :ride:  

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Or was it what I've heard of called "pipe banging", or something like that,  caused by the o-rings being worn out?

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No, it was likely the steel pipe spigot vibrating against the inner surface of the alloy flange on the cylinder. Its a close fit and when the orings take a set from heat and time, or when the pipe is hit and tweaked, the two parts can make contact. Keep fresh orings as the aluminum cyl flange will be damaged from vibratiion and the hard steel pipe spigot. By in quantity from a supplier, much cheaper. Viton is what you want.

Edited by GP

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