912 ULS starting but stalls

Yesterday the trike manufacturer, a fantastic, patient genius by the way, came over, listened to woes, sat in it and started it right up with "no gas and no choke". 😆  Just like "the dentist office" joke. 😁😂

Today I went out there and followed the same no gas and no choke.  It caught immediately and ran for less than two seconds.  😨😫😪

Sooo..........I got it going, wamed up, adjusted the idle and synched the carbs.  +1 at ~3400 rpm. All other speeds = center green.  Started instantly, ran slow and then kicked up all the times I restarted to adjust.   That is a lot as I am not so hot at the job.

Sooo... now it can cool its jets 😉 and I will get back to it ASAP.

🙏

Rotax Wizard wrote:

Hi Jeffrey

To be clear the soft start is a circuit within the modules that is excited when you first power your starter, normally from the starter solenoid.  What this activates is a timer in the circuit that delays the advance from start timing to run timing.  This is the 3 to 5 second delay you hear.  It is not directly related to idle but you will feel the advance and cant go to high throttle until this moves to the 26 BTDC degree run timing.  Engines from before 2010 did not have this feature and had different timing for the starting of the engine.  (4 BTDC as compared to 3 ATDC on start) 

I disagree that starting on a single mag (single module actually) will give you a rough start.  This suggests something wrong in your system.  On one module you still have one spark plug active in each cylinder.  Cold starts run badly normally because you are too lean on fuel while the engine is trying to warm up.  

Cheers

Not to say it will, but it can give a rough single-mag start. Here's how! On an even slightly chilly day, shut the engine off a few miles out, glide to the airport, fly a full pattern and land. Start the engine, taxi at idle a mile or so back to the hanger and shut down. Come back the next day and do the single mag start, if it starts at all. Yes, I fly a motorglider burning 100LL and can give a master class on how to load up spark plugs. But it's only an extreme degree of a normal LSA approach and landing. YMMV ...

Well, humm.

At Hobbs 336.1 I checked the plugs and gap and reapplied the silicone heat transfer paste.  Yesterday at 348.1 I replaced the the plugs and lo-and-behold it started "normally".  😁 67°F, full choke, no throttle.  Started immediately,  ran rough ~3-4 seconds, picked up and I added throttle while removing choke to 2200 rpm for warm up.  Just like the last 4+ years.😉

A bit embarrassing for me but I had ruled out he plugs since inspection at 336.1 hrs.  My bad. 😐

Now, about those plugs. 😱 See pic.

Jeffrey Schinkel wrote:

Well, humm.

At Hobbs 336.1 I checked the plugs and gap and reapplied the silicone heat transfer paste.  Yesterday at 348.1 I replaced the the plugs and lo-and-behold it started "normally".  😁 67°F, full choke, no throttle.  Started immediately,  ran rough ~3-4 seconds, picked up and I added throttle while removing choke to 2200 rpm for warm up.  Just like the last 4+ years.😉

A bit embarrassing for me but I had ruled out he plugs since inspection at 336.1 hrs.  My bad. 😐

Now, about those plugs. 😱 See pic.

HI Jeffrey...you put far too much paste on the plugs.  The instructions are for a light coating and not to cover at least the 3 threads near the electrode ends.  Too much paste interferes with the grounding of the case.  

Cheers

Rotax Wizard wrote:

Jeffrey Schinkel wrote:

Well, humm.

At Hobbs 336.1 I checked the plugs and gap and reapplied the silicone heat transfer paste.  Yesterday at 348.1 I replaced the the plugs and lo-and-behold it started "normally".  😁 67°F, full choke, no throttle.  Started immediately,  ran rough ~3-4 seconds, picked up and I added throttle while removing choke to 2200 rpm for warm up.  Just like the last 4+ years.😉

A bit embarrassing for me but I had ruled out he plugs since inspection at 336.1 hrs.  My bad. 😐

Now, about those plugs. 😱 See pic.

HI Jeffrey...you put far too much paste on the plugs.  The instructions are for a light coating and not to cover at least the 3 threads near the electrode ends.  Too much paste interferes with the grounding of the case.  

Cheers

Dang! 😠   

Will this cause just one cylinder to carbon up but not the other one fed by the same carb?  

They all have about the same "too much" amount.  Some even more.  But it's a close race.

I have never seen carboning of half the plugs fed by the same carb.  But, this is my first Rotax rodeo. 

Hobbs-300. replaced with new

336.1 inspected.

348.1 replaced (yesterday)

Unfortunately I do not have the time when hard starting began.  I guess it came after 300 since I inspected the plugs at 336.1 as part of my trouble shooting, where they looked fine and all gaps were good.  But I usually fly about an hour.  I really don't think it was 36 flights before I asked around and then  finally came here to post.  More like 6 - 10 in my mind.😐

What is the best way to clean the cylinder plug threads without pushing the silicone into the cylinder?  I can think of a complicated way.