12 pro mid range sound

[Travin]

so I have a 12 pro that picked up with a blown motor rebuilt top to bottom with new reeds, it is giving me a funky sound out of the exhaust (brrbrrrrrbrrrbrrrbrrrbrr) from 3k to 5800 rpm go to 6k and sound is no longer there top end sounds and runs strong but drop back to 5800 and its back can notice a small power loss but not huge. have checked for leaks double checked the reeds for fluttering and nothing is showing a problem, haven't checked the power valves yet but planning on it tomorrow just to double check, checked spark on both cylinders while running and didn't look like a loss of spark. is there anything else that you guys can think of to check?
there is a plug (female) that has no mate right above the fuel rail and have looked all over the sled and everything is plugged in? my only other thought would be I switched the pickup coils on the stator but don't think I did and not sure if you can. any help you guys can give would be awesome

 

[05rmksteve]

Definitely check the power valves.

 

[Travin]

so pulled the power valves this morning and they were completely full of oil and one bellow has small wear marks where it could leak so think this is the problem. but another question is there is movement on the guillotine in the housing it moves up and down freely of course but has back and forth movement, how much movement is acceptable?

 

[sledtahoe]

They do have some play ,but leaking would not be good if it's sucking air.

 

[Travin]

so cleaned up the power valves real good and put them back in and still have the sound at the same rpm range. have looked for air leaks and nothing. pulled the plugs and plug wise it don't look like a lean condition friend is thinking something came apart in the can and is blocking the exhaust at that rpm range?. but here lately I have been fighting a exhaust temp problem so put the sound on the back burner. check engine light comes on with the 173-3 code (high voltage or short to positive) checked for shorts and cleaned grounds and putting a new voltage reg on it today.
nothing like a cheap sled

 

[Octanee]

hard to know exactly but i know my pro's made some small blurble noises in the lower rpm at times, maybe similar to yours, it just seemed to be how they sound and run... It'll cut in and out of a normal 2 stroke hum into some slight blurble down low, usually slow trail speeds and lower rpms, once moving down the trail its a smooth hum. that said It had no performance impact,

The exhaust valves should be dry on the back side of the diaphram but under them they do get very oily, they dril oil out of the solenoid controled vent line. again normal.

that said,my 2 2011pro rmk's were never kind to me lol even my spare one that maybe gets ~400km a winter just wont behave.... frustrating.

 

[Travin]

Power valves look good, new bellows and no oil on the outer part. Going to go back through the wiring again and see if I missed anything