Stratus vibrations

[Alba01]

Hi MA experts!

I experience some kind of vibrations on the new pre-BW frame, that are mostly indicated at tail boom area, but even throughout the whole frame. I use YS91SR @ 1850 rpm (tryed changing rpm from 1780 to 1900 with no positive result). 8,18 ratio. Total fan runout is 0.001''.
Both screws, that hold boom supports, worked themselves out of horizontal tail boom clamp, now there's not enough plastic for screws to hold themselves in place.

I believe it's engine related, as after I've hitted throttle hold switch, all the vibrations stop. Another issue that is pretty strange is that while turning the main gear by hand anti-clockwise against the pinion, it doesn't turn smooth, some uneven friction is present, but if you turn starter shaft say a halv turn, than it could become smooth. I disassembled the frames yesterday (separated lower from above) and tried to figure out why it behaves in that way.
I've found out that it's possible to reproduce that effect without the engine present. I thought that the clutch bell assembly and lower clutch block assembly are self-aligned (as there are no possibilities of doing it), but may be it should be done in some other way?
One more thing, if you remove the rubber o-ring, that goes on the bottom of starter shaft, everything is then smooth, with no friction.
But then, if the o-ring is not there, the clutch bell could simply fall down on the clutch.
Or could my starter shaft/clutch block be bent?

[WayneBrown]

sounds like a clutch to engine alignment issue.
check the gap between the clutch driver and the fan hub in several places and report your findings back.

[Alba01]

Thanks a lot Wayne, I'll try that!

Anyway, I've ordered the clutch block assembly + clutch bell assembly because something isn't true, even with theengine removed.

Are the "remove the glow plug, run the starter with engine mount srcews loose and tighten the screws in a cross pattern" or "loosen the engine mount screws a bit, then hover for 30 seconds or so and tighten the screws without twisting the frame" methods not relevant? I did according to both of them....

[WayneBrown]

they are relevant, if you have a new engine that is real rich you may get a slight twist in the alignment. Thats where the feeler gauge method comes back into play, just to verify alignment.

[Alba01]

Ok, thanks again Wayne!

[DavidH]

The oring on the clutch shaft that is located in the inner recess on the clutch. That oring is there to space the clutch from the clutch bell. The oring only touches the inner race of the bearing located in the clutch bell. If you remove the oring and fly the model. Then the clutch bell is most likely going to drag on top of the clutch.
David

[Alba01]

Thanks Dave!

I understand the meaning of o-ring. I am though concerned that my pinion bearing could be shot as when oring compresses the bearing, it becomes notchy...