Re: 912 ULS with 460 hours built in 2008 1000 RPM drop during Mag test
by michael Vadney » 2 years ago
Ordered the new 6-pin harness and some o-rings, $1000 ducks.
Here is the offending part. Well, hopefully anyway.
Re: 912 ULS with 460 hours built in 2008 1000 RPM drop during Mag test
by michael Vadney » 2 years ago
Can someone explain this statement from the heavy maintenance manual, 74-00-00 page 46.
CAUTION: As the trigger coils are no longer centered and the screw has clearance in the oblong hole, during adjustment of the gap (IH02), all trigger coils must be pressed CLOCKWISE up to the limit stop.
I was just going to press the loose trigger coil squarely up against the flywheel with a feeler gauge in between. Wouldn't twisting the pickup on its mounts make the coil sit diagonally on it mounts?
Thanks!
Re: 912 ULS with 460 hours built in 2008 1000 RPM drop during Mag test
by michael Vadney » 2 years ago
UPDATE: I installed and adjusted the new pickup harness for just under $1k.
THE SAME ISSUE STILL EXISTS. Majorly bummed out on that.
I've also noticed that it seems to be progressing in that its taking more to start the engine, choke or no choke. When it does fires up and seems to run in a slightly reduced fashion and then instantly if "clicks" into a stronger, smoother mode. This happens maybe 10 seconds or so past startup. Not that it was real rough at all, but VERY noticable.
Does any offer a phone, fee for advice type help for the 912 ULS? I can't afford to just keep replacing parts and my diagnostics seem to be at an end.
Thanks
Re: 912 ULS with 460 hours built in 2008 1000 RPM drop during Mag test
by Jeffry Stetson » 2 years ago
Hum, interesting problem. Several comments:
1) The green stripe modules are the *old* ones. Yet you have the "new" 2x6 pin connectors. IIRC there was rather a mix of old/new versions around the same time they switched to the heavy case versions in about 2006. Kind of crappy for Rotax to do that, but I guess they had an excess of old modules laying around.
2) Trigger coils can pass a resistance test, but still fail to work properly. Reason? The permanent magnets can get weak over time, especially if they ever got too hot. This happen to me with the crank position sensor on my 1998 Ducati.
3) Your description of the increasingly difficult starting is exactly what I experienced a couple of months ago. What I found was that after "professional" overhaul, the float arm adjustment was way off, allowing too much fuel in the bowl. This flooded the carb, so it wouldn't start with the choke engaged. The same effect would happen if floats were sinking or fuel pressure was too high or if the bowl valve were sticking or defective. Once running, it seemed fine, but the plug colors told another story.
4) 4) Soft start. The old start circuit set the timing to 4 degrees BTDC which gives an “angry” start and risks kickback which may destroy the sprag clutch or starter. The new modules use 3 degrees ATDC which eliminates these problems. Both set to 26 degrees BTDC while running. Soft start modules work on the old engines if one adds a wire to the starter which triggers the function. But, to get full benefit, the flywheel must also be changed. The bumps of metal on the earlier flywheel are too long for it to work well; the new version has a shorter bump. There is a box to give soft start to the green stripe modules, but it’s a waste of money if/when the old module dies.If the starter sense wire fails, that side will be stuck on 3 degrees ATDC with a huge power loss. Do you have the soft start add-on box?
Sadly, IDK what's happening with your engine since wire and module swapping still has "R" remaining the bad line. In your position, I'd start looking at the pulsed signals (trigger, plug wire) with an inductive pickup displayed on an oscilloscope.
Re: 912 ULS with 460 hours built in 2008 1000 RPM drop during Mag test
by michael Vadney » 2 years ago
Thanks for the reply.
The resistance check between all of the old pickups and the pickups on the new harness are all the same within 2 Ohms. I don't believe that I have the soft start feature on this engine and there is no separate starter wires going to any where but the starter. Again, when (not every time) that the engine starts up it can run like its running on one mag and then suddenly switch to a couple of hundred rpm nice and smooth not that the lower rpm was that rough.
The oscilloscope does not sound like a fun time. Finding one could be a problem too. This is a brand new harness with pickups so I don't believe that is the issue.
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