Rotax 80hp, ignition problems

[JorgeEC-YUQ]

Well that is good news since I have a used 912 100 hp seating on the hangar.

My 80hp has the old style connections (it's 12 years old) and the 100 hp has the newer style. Other than that ... I might just replace the full ignition system from one to the other and see what it does.

The pick ups were gapped to the rotax manual value but since they are not adjustable, how can I make it to reduce that gap? Could I gently force it ?

Reduction gear was tested on the bench and yes, those spring washers were replaced.

Yes, I did the tracking on the prop tips and they all go thought the same point. But I don't understand what you meant with prop flange?

Thanks for all your inputs!
Jorge

[Av8r3400]

I'm talking about the spark plugs themselves. The gap from the electrode to the ground strap.



I like to gap from .020" (,5mm) to .023" (,6mm). They work better, IMO.


Indicating the prop flange is easy as putting a dial indicator from the engine case to the propeller flange and rotating the engine to see if the flange rotates straight or if it wobbles.

[Dusty]

Just a randome thought ,you sound to have different symptoms,but one more item to eliminate.
Try running without your muffler as the baffles can fail giving strange running.

[Wheels]

Don't do that!

[TY2068]

I'm sure you've looked at things suggested in this link but I thought I'd post it anyway. I'd bet it's something simple when the problem is finally discovered. I've always been told to never run an engine without the exhaust. Valve damage could occur or something along those lines. Would there be a way to check the exhaust without running the engine ?

http://pointsforpilots.blogspot.com/...ngine.html?m=1

[Paul Z]

The pick ups were gapped to the rotax manual value but since they are not adjustable, how can I make it to reduce that gap? Could I gently force it ?

If you are referring to the Trigger Coils, I have tried recommending trying to adjust the trigger coils to someone else and got shot down. However, having recently taken the Rotax Maintenance classes, they stress the gap of the Trigger coils is very important, to the point of saying they check the gap on new engines to make sure it is correct. Even though there is no slotted hole on the trigger coil, there is probably .006 to .010 clearance between the fastener & the hole in the trigger coil mounting hole. They recommend loosen the fasteners, taking a flat blade screw driver, lightly pry it away from the flywheel, set the gap and the torque the fasteners. You might consider giving that a try.

[JorgeEC-YUQ]

I see what you mean. Yes, I tried that, reducing the plug gap and also did check the flange. No improvements.

I tried without the muffler and there was no change. It's good to know is not a healthy procedure for the engine however ...

Thanks for sharing that post. I've had read it before and I had big hopes that would be it, but "unfortunately" my ignition cables were all properly installed ...

I was referring to the trigger coils indeed. Sorry, we call them pick ups in my place. They are gapped to the manual values and rechecked several times ... Could I try to make that gap bigger? Smaller?

I also tried by isolating the engine from the plane. I feeded new fuel directly from a canister to the carbs without passing trough the pump, didn't work. I also disconnected the grounding cables from the CDI's to the switch toggles ... same vibration.

Since all logical steps are taken, I am planning to spill some headless chicken blood, during full moon, while dancing around the plane and see if that helps.

Any other ideas before I sell the thing?

Thanks for your inputs,
Jorge

[Planesmaker]

Hi Jorge, can I ask how are the compressions? After you have tried everything else, maybe you could pull off heads ( start with 1&3) not a big job and take a look inside, possibly piston damage. Another possibility although rare would be the crank has rotated out of alignment at a conrod attachment pin( cranks are pressed together ). Just a couple of things to look at. Tom

[TY2068]

Have you replaced the main ignition switch and others ?

[Paul Z]

Also make sure the Spark Plug Connector Boots is screwed on to the Spark plug wire and use dialectic grease. I was having a big drop on my mags, and I found one of the Spark Plug Connector Boots was not screwed on to the spark plug wire. I started removing the Spark Plug Connector Boots and looked at the ends of the wires to see if there was an indention on the core of the wires, I found one that hand not even touched the wire. Once installed properly, my mag drop issue went away. If it is not making a good connection it is having to jump the gap or Arc which is effectively resistance.

Check the Pull off of the Spark Plug Connector Boots, it's probably is good but it should check 30 Nm or 265 in. Lbs. Just to make sure the Spark Plug Connector is staying on the spark plug, and has a good connection.

Another suggestion, check each of the Trigger Coils, Spark Plug Connector Boots, Ignition Coils for proper resistance, per the Heavy Maintenance (74-00-00 page 22). If the resistance does not meet specification it's probably a pretty good suspect of a problem.