YAIP? (Yet Another Ignition Problem?)

[Ed Cesnalis]

I'm not giving you a hard time Tom, I just don't know how to interpret your post.

 

I'm the worst offender here.

[FastEddieB]

Headed over to the airport...

 

But first, some thoughts:

 

I will stipulate that Roger has at least one order of magnitude more experience with Rotax engines than I do. Possibly two!

 

So, his experience is highly valued here and I take it very seriously.

 

Hence, his take that my slightly higher drop on ignition two than ignition one being caused by carb problems will have me pulling my float bowls - probably not a bad idea since the last time was about seven months ago and it never hurts to take a look.

 

And I fully understand how Roger, after troubleshooting a hundred or more rough running engines and having it turn out to be carb related, would make that first assumption and usually end up being right.

 

But...

 

In Zen, there's something called "beginner's mind". Sometimes someone with less experience can see solutions that a more experienced person might not, not being "primed" to go in any one direction, as it were.

 

And then there's the old scientific method.

 

It still seems to me that a bad carb on one side would not favor one ignition over the other - or at least it has not yet been explained to me how.

 

And I'm not sure I accept Roger's assumption that an ignition problem would have to manifest itself equally at all rpm. I've seen ignition problems that were present at idle that went away at higher rpm, and some that idled just fine but broke down at higher rpm. Added to the mix is my SoftStart module that is supposed to retard the #2 ignition timing under one set of circumstances (12v at the starter solenoid) and then advance the ignition timing back to normal after the 12v is no longer sensed. Hence, maybe the drop I'm seeing at and around idle is due to the SoftStart keeping the timing retarded when it should not be.

 

In any case, my plan is to check, clean and gap the plugs, check the float bowls and jets (at least visually) and maybe check the SoftStart connectors and hit them with some Stabilant22™ for good measure.

 

I'll report what I find this afternoon.

 

And this discussion is NEVER meant to be argumentative or confrontational - I'm always open to new ideas and can only learn by questioning my preconceived notions and thought patterns.

[Roger Lee]

Hi Eddie,

 

I forgot about your soft start module and since I don'y have enough experience with trouble shooting issues with them I don't know how it might fit into the mix. The only sure way to rule it out if you can't find any other explanation would be to disconnect it and let the original ignition setup take over. Unless there is something glaringly obvious in the bowls you may need to pull them for cleaning because any tiny particle not seen in a bowl but in another orifice can cause your problem.

 

Diagnosing anything by phone or email and not in person is tough and can be problematic and why most doctors won't do it. Too many things get missed or something the trained eye might catch in person is important. Plus in person you get to have a far better history and info exchange. I choose to pick the most common problems given the symptoms that is reported in the text. Fuel delivery issues can be intermittent for us, but usually if you have a bad electrical spark problem it shows up at low and high rpms. The problem with too low an rpm check is the rpm spread and the engine miss can be so small as not discernible by the user. I have guys come in all the time that say how smooth the engine seems and I tell them I think it's off. Put the gauges on and they're off. It's just they usually get to hear only one engine and don't work on any, but I get to hear hundreds and put gauges on all of them. I'm not better than them by any means I just get exposed to more problems than the average owner and have been bit in the butt by not looking in the right place the first time just like anyone else..

[FastEddieB]

Roger,

 

I do appreciate all the help.

 

Basically spent most of the day bonding with my Sky Arrow.

 

1) I need to decowl on a more regular basis. I found the strap supporting my coolant tank had broken:

 

 

Took the broken strap to a homebuilder friend's house and we fabricated another.

 

Also found the plug cap for the lower Cyl 2 plug was very loose and one of the drain hoses from one of the drip trays was split at the nipple.

 

2) In any case, the plugs looked fine.

 

 

I checked them and they were all at .024", which I think is the winter setting anyway. Cleaned them up and reinstalled with fresh paste (for Andy's benefit):

 

 

3) Pulled both float bowls and they had tiny flecks of something, but nothing that I think would block anything:

 

 

 

 

The jets in the bowls (that's the idle jet, right?) were both clear and the two jets in each carb appeared clear looking at them with a bright light and a mirror.

 

Confirmed that the "choke" levers were against the pins both at full and zero control movement - that one has bit me before.

 

Anyway, buttoned everything up and it started right away with no leaks.

 

Still, she still seems just a bit rougher on ignition two alone than ignition one alone. But both at 1800 and 2000 rpm the drop was 200 for both, but with more roughness/vibration on ignition 2. At higher rpm, still fine.

 

Anyway, I'm satisfied for now its nothing major. Maybe play with it more later, maybe taking the SoftStart module out of the circuit to see what happens.

 

In any case, feel confident enough to fly to Indiana tomorrow to meet up with Karen. I'll advise how it goes (unless the weather is much worse than forecast tomorrow).

[Roger Lee]

The tiny carb debris looks normal from what I see in everyone else bowl. Did you put a set of carb sync gauges on the carbs? A loose plug boot can cause roughness and you can usually see it if you do a 3500-4000 rpm mag check. using too low an rpm doesn't give enough spread at times to see any rpm difference or roughness.

[FastEddieB]

First, I don't have a set of gauges - probably need to get some. What do you recommend?

 

Second...

 

Yesterday, all loaded up and ready to roll to Indiana, I taxied out, did a runup and began my takeoff roll...

 

My three "on the roll" checks are "Canopy - LATCHED", "Airspeed - ALIVE", and "RPM - 5,200".

 

Unfortunately, the power felt "soft" and I was only getting about 4,500 rpm. Aborted the takeoff, and could not get static rpm above about 4,500 rpm.

 

Taxied in, and with the help of a friend decowled, checked the plug wires (one did go on with a couple more clicks), and pulled the float bowls. They looked fine, with the exception of a tiny bit of clear silicone looking fleck sitting on the surface of the main jet of my right carb. Not blocking it, just sitting on it. Other jets looked clear.

 

Put the bowls back on, started up an "VIOLA!" - better than 5,000 rpm static runup.

 

At this point unsure what caused the prior problem. Had that fleck blocked the main jet, I would have suspected more than a smooth power loss on takeoff. I did not see any problem with the way the float bowls and floats were installed.

 

Weird.

 

In any case, plane did fine on the subsequent takeoff and on the two roughly two hour legs to Indiana, where I am now.

 

As an aside, at my next annual in March I do plan on overhauling my Bings, which are original from 2007, so it's about time.

[Roger Lee]

If it crops up again Eddie you'll need those gauges and have to pull the offending carb, strip it and flush it. Debris can hide in other places that you can't see and the bowl may look clean. Just had one like that this last weekend. Ended up pulling both carbs and stripping and cleaning to find the problem. It's now done without any more issues.

 

Sometimes it's faster to take what you think is the long route to the finish.

[FastEddieB]

Just to let everyone know I made it to Indiana and back, arriving home about an hour ago.

 

Not a hiccup from the ROTAX, full 5,200+ rpm on every takeoff.

 

Details and photos to follow.