Torsional vibration

Thanks.  Yes, I have the locking bolt.  The video showed removing a spark plug and finding TDC to find the v-notch.  I've gotta wonder if just using a flashlight and slowly turning the prop while looking for the mark may be easier...

You can try with a flashlight but it's hard to see a couple inches down into what is a pretty small hole, and the notch itself is not particularly noticeable.  

When it's properly in place, the locking bolt will protrude a half inch or so, IIRC.   If the bolt only goes in halfway, it's on top of the counterweight, but not in the notch.  If it goes in ALL the way, you have missed the counterweight entirely.

Hi John,

"I've gotta wonder if just using a flashlight and slowly turning the prop while looking for the mark may be easier"

All I do during an annual is remove plug screw and use a flashlight to find the "V" notch to put the locking pin in. Don't lose the crush washer. 

I do leave my long Tee handle allen wrench in the locking pin. That's my red flag to take it out and not accidentally leave it in.. It's easy and takes no time.

This RO site has a very good video explaining the friction torque check process at:  https://www.rotax-owner.com/en/videos-topmenu/elearning-videos/60-friction-torque29

This video has a great depiction of the crankshaft V-notch starting at @ 4:30 mins.

I was able to perform the process.  Tip to anyone else testing theirs..   I initially tried to find the v-notch using a flash light.  It was very difficult.  I ended up using a mirror and looked at the flywheel.  Much much easier method.  You just line up the trigger coil and the magnet attached to the flywheel to give you TDC. 

Anyway, friction torque was in spec at roughly 14lbs measured at 30 inches.

I then ran the engine again, not as much issue this time.  When I did a mag check however on circuit A, I got a drop of around 175 RPM, circuit B was around 150 RPM.  Note, this is prop RPM, so engine RPM would be around 398 and 340.  I think my Diamond Katana AFM listed maximum drop of 150 which is on edge.

Maybe this is an ignition problem?