Hard Starting 912 ULS 400 hours #120330

My RV-12 has been giving me starting trouble for over a year. Recently when it seemed to have no indication of any life when spinning the starter, I turned it over to the local mechanic who works on Rotax 912s. He checked the ground on the ignition system, brought it back running. I went for a spin, it worked fine. Letting the plane sit for a couple of weeks, and tried to start. Same symptoms. Back to mechanic. another round of ignition checking,, nothing wrong there.

Then the mechanic gave me a lesson on how he starts my plane. Full choke, and if it doesn't hit right away, he says to push the throttle in all the way and back out. That seems to work, but is that what the rest of you do in 50 degree weather? I don't remember having to do that in the first 5 years I have owned the plane. Thoughts? Mark, Glendale AZ

No that shouldn’t happen, especially from cold, with choke fires right up.

Are you ever over at falcon field in Mesa ? Would be happy to take a look at that for you.

Have you had the carbs serviced ?

Have you checked that the rubber union between carb and intake is not cracked on either side ?

Any difference in readings for ignitions when doing the check in run up ?

What are your EGTs in flight ?

With 400 hrs time in service, what level of inspection and servicing has been done on the carburetors?

Mark,

I’m based at GEU too. The only time I have experienced what you describe is when the idiots who overhauled my carburetors swapped the choke assemblies right to left. When I figured it out and swapped them back everything worked great.

Rich

When overhauling carbs - it's best to do one at a time so parts don't get mixed L-R.

YMMV... but I don't think I would tolerate over a year of hard starts with my Rotax 912 ULS. It would bug the H3LL out of me so much, I'd either tear into it myself, or pay a real Rotax Pro to rebuild the Carbs until it is right, again. 2012 RV-12... 212 and about 225 hrs on it and climbing.

Currently, my engine starts up instantly, throttle shut, fuel enrichener pulled full back on a cold motor. 42F this morning, motor leaps to life, instantly.

I add throttle and then reduce enrichener circuit shortly after start up, and set for 2300 to 2500 rpm, where my motor runs very, very smooth, while warming up.

If you are around the Tucson AZ area, get ahold of Robert Lee, he knows Rotax product, through heavy line repair, and could probably get you squared away promptly. A previous example: https://www.rotax-owner.com/en/rotax-owner-community/6472-rotax-service-class-in-tucson-az

First thing I would do is pull all your plugs, put new plugs in, and make sure they are gapped properly.... .022" to .025". Next thing I would do is fill up with premium unleaded instead if 100LL, if I'm not using 91 octane premium unleaded Mogas already.

I'd also check float weights and levels, and for matched cylinder head temperatures and exhaust temperatures, to see if one side is running hotter than the other, or shoot them with cowling off with a laser temp reader and compare. This would indicate if you've got a vacuum leak somewhere.

Or just get your plane to someone that throuroughly knows Rotax engines inside and out, they aren't hard to find there in AZ.

Jim,
I agree completely on one at a time overhaul, or at least physically segregate the parts so there is no potential to mix them. As I recall the ROTAX documentation even calls for that. That’s hy I referred to the “professionals” who overhauled mine as idiots. Next time my carbs will go to Lockwood since they have such a good rep with the ROTAX stuff.

Rich

RFSchaller said:

Jim,
I agree completely on one at a time overhaul, or at least physically segregate the parts so there is no potential to mix them. As I recall the ROTAX documentation even calls for that. That’s hy I referred to the “professionals” who overhauled mine as idiots. Next time my carbs will go to Lockwood since they have such a good rep with the ROTAX stuff.

Rich

Click to expand...

Don't need to service mine, yet... just seeing if when I do need it, is it a quality operation they perform?

Has anyone used California Power Systems, a division of Aircraft Spruce, for Rotax Carb rebuilds? They also offer the service. https://www.cps-parts.com/catalog/rtxpages/15-05914.php

I used CPS. Draw your own conclusion.