Sunken Float

During my last Annual Inspection I overhauled the Bing carbs as they had exceeded their 200 hour mark. I did this despite the feeling that leaving things that work alone is usually the best strategy.
My main worry was that after all the issues with the Bing floats that Rotax had for a long time, I should probably go and finally see how they were doing after such a long time submerged in gasoline. And indeed, I did find two that were a bit heavy. Mind you though that despite their weight I experienced no issues with the engine. Not at idle or low RPM and of course not at WOT.

A few weeks ago I started my engine in the morning and found it to be reluctant to come to life. It sounded a bit like a Diesel engine, with heavy vibrations and very rough running coming out of idle, barely maintaining idle speed. My first guess was that one of the cylinders was not firing properly.
Pushing the idle during warm-up close to the 2500 RPM mark made it better, and the engine ran fine at higher RPMs so I decided to go ahead and take off.
At my destination I throttled back to start the decent and the engine behaved a bit rough again and I could smell gasoline. Yeah, that definitely worried me, so I grounded the plane after my return to give the engine a thorough inspection before further flight. As a busy man I didn't get to it until last weekend where I took off the carbs opened the bowls and re-inspected the floats.
One of the just recently replaced floats (one of those that were supposed to finally end the problem of sunken floats) weighed in at 8.5 grams!

Notice the markings on the float in the picture above. This is definitely a new style float and it took just a few months to almost triple its original weight. Given the price of these parts this should never ever happen. The other new style float I found was at 4.5 grams and two original floats I left in the carbs were at or below 3.5 grams.
I replaced the 8.5 gr float with a new one and matched the 3 others for lowest pair weights and installed them in the carbs.
The engine fired up and ran just fine, no coughing, no fuel smell, no rough running at low RPM or idle.

I am getting tired of these Bing carbs and am thinking again about replacing them with a TBI...

-- Update --

I researched this matter a bit more as I was very annoyed by the fact that these "latest" floats were still showing the old problem of absorbing fuel. Turns out, I must have bought the carb rebuild kit right before a newer new float was released. I have the 861-185 version which was obsoleted around September/October last year which is right after I had bought my rebuild kit. The latest product number is 861-188 and the leisurely determined price is a whooping $151 for a pair. Which is about 15% of a TBI ....
I found details about the float tale here: http://www.dogaviation.com/2017/10/switching-to-newest-improved-carburetor.html


The following picture is a nice example how you can identify a float issue without even utilizing a scale.

When the brass pin that is supposed to push against the lever that controls the inlet valve on the carburetor is below the fuel line in the bowl, it cannot perform its function properly. The left one is clearly below that line!

1st Engine Run

You would think I had something better to do on a searing hot day in Tucson but to push the plane out of the carport so I could fry my brain in the open sun and running the engine for the first time - but, no, I had not!

Early, at 8am when it was just 85 F, I started closing everything up and putting the canopy back on and topped off the charge of the battery.

I threw in the cushions on the left side after installing the seat back.

I even checked what the fuel pressure would be without the engine running but with the electric fuel pump on.

2 psi - that looks a bit low and I will have to check with VAF to see if this indeed correct to be so low.

With the help of the Van's tow-bar I pushed the plane out into the driveway and made sure that the nose wheel and - more importantly - the prop would be still on or above the concrete ramp. I was really concerned about picking up small debris or gravel and so I swept the carport clean.

And here is the video of the first run:

Inside the cockpit I took some photos of the SV display during the 5 minute run. Note that I had forgotten to open the fuel valve which resulted in 0 psi fuel pressure despite the engine running (with the fuel from the float bowl). Follow the checklist!

Engine up and running, no fuel pressure - valve closed!

With the valve open fuel pressure was always high, close to 6 psi

Fuel flow zero? Great consumption! Oil psi drops from 64 to 52 when warm.

Higher rev and finally some way too high fuel flow. 

One noticeable but familiar problem is that the ignition A circuit loss drops the RPM by 150 revs which exceeds the 120 allowed by Rotax. I had the same "issue" with my previous bird that also had a 912ULS, so I won't worry too much about it. Ignition B circuit loss dropped RPM by around 90.
Overall it ran fine although somewhat rough even at 2500 rpm and so I warmed it up at 2700. It was very smooth above 3000.

After the run I pulled her back into the carport and set up a fan to cool the engine. I will yet have to check the lifters.

Oh, and we hit 107F when I was done ...

Engine Purged (and Burped)

When I got home I found some items I had ordered from Amazon to get the purge done. It was a sensitive low-pressure gauge (30 psi max.) for Acetylene and a Powermate 1/4" NPT regulator that looked much more solid than the flimsy HF parts. I could not get an HF regulator to safely provide 7psi pressure, so I gave the Powermate a shot.

I put the parts together and was very pleased with the quality of the Powermate regulator. It was easy to set it to as low as 3 psi and it smoothly came up to 7psi which was my desired purge pressure.

A 1/8" braid fits the spillover tube perfectly.

Please note, the red cap on the return hose is only to prevent anything from getting into it during setup. I removed it for the actual purge.

7 psi set up and flowing. The canister is constantly leaking air by a bit so there is a hissing sound during the purge.

Pressure started to build up slowly after a few turns. I could not get my camera set up fast enough before the 25 psi had bled back to 10 psi.

You do not need a second person to watch the gauge by the way. If you turn the prop as quickly as you can and then quickly get to the display after 5 or 10 turns you will still see the pressure for a few seconds before it slowly bleeds off.

You do have to watch the canister though. Mine was full beyond the max line and after building up 25 psi, it was way below the min line. So I filled it up again and repeated the purge to be sure I had not sucked air in.

After putting the engine back to correct setting, torquing the spark plugs to 15 ft/lbs. again, I burped the engine to remove the accumulated oil from the engine housing and found the oil at 3/4 of maximum.

I think this baby is ready for the first start!

If the fuel system holds the fuel that is ...

Prepping the Engine

It is definitely close to the first engine start. I filled the cooling system with 55% DexCool and distilled water.

The stuff looks like KoolAid(tm), so keep it out of reach from children!

After mixing 1 gallon and filling both tanks, I had about a quart left but I am sure there is air trapped in the system that will come out soon.

Then I filled the canister with oil. I was ready to give it the 3.5 quarts but the canister was filled to the top after less than 3. I assume this will quickly disappear when I purge the oil system.

I also sent off my fuel cap and the data plate for engraving.

Plumbed Up

With another day off from work after Independence Day, I used the cooler (or better: not so hot) mornings to continue work on my RV12.

First I replaced the plastic lock nuts on the throttle cables with ones from metal - MS21042-3 to be precise. This is the better lock nut in hot environments and the engine compartment is certainly such an environment.

Then I had to reroute the flex hose that runs fresh air to the voltage regulator. As you can see the way I had routed the hose before, prevented the air filter from sliding on.

Routing the hose so it would run under the water hose in this critical area did the trick.

While working on that water hose, I noticed a possible chafing area between the hose and the forward motor mount as it touch it. I put a cushion in form of a leftover piece of that water hose over the motor mount and tied it down.

Then I safety-wired both air filters.

Considering how tight it is around those air filters, there is literally no way how they could ever fall off and away from the aircraft but it's easier to do now than during certification when they might require you to do it anyway.

So, finally I felt like the engine compartment was good enough to be left alone for a while. The next step was to open up the avionics cover and finish the plumbing of the Pitot line and some fixes to the wiring.

Thanks to the Stein quick connectors, the plumbing was quickly done - including the splits for the hook-up of the additional steam gauges that I will add after certification.

This is the T for the static line which will run to the ALT and ASI instruments

This T is for the Pitot line that runs back to the ADAHRS and the ASI

The open ends are plugged for now and both pneumatic systems should be ready for testing now.

In this VAF article I had learned that there was a wire missing between the Garmin radio and the AV-50000 black box that made it impossible for the SkyView system to read the currently selected frequency from the radio. The rest of the wiring between the black box and the SkyView system was in place however, so it appeared that adding the missing wire should fix this little "problem".
It is indeed a bit tricky to add that wire as space is extremely limited but others had tried to use a pair of needle nose pliers and succeeded without removing the radio tray.
So I followed those tracks to do the same.

With the help of a small mirror and my smallest needle nose pliers I was able to insert the female socket into the plug (pin 3, red wire is pin 1) without removing the tray.

The question now just is, if I used the correct size socket. I used one that is for male .040" D-sub pins which is on the other end of this wire and hooks up to the AV-50000's COM/NAV port (pin 6, red wire indicates pin 1). I put this wire together from two cut off pieces from harnesses that were not used anymore. So the wire that is yellow on the radio side turns white/orange on the AV-50000 side.

I was even able, after years of pulling my joints out of their sockets working in all the tight spots on the plane, to figure a way to get a couple of tie-wraps installed to secure the wire behind the radio tray.

By then it was approaching noon and the temps their usual uncomfortable level of 100 or more and I decided to seek shelter from this searing heat inside.

I think the additional antenna installations might be next. At least the small ones for the ADS-B receiver and the PCAS. I might leave the APRS one off for now as it is really large and very visible.

Engine Controls Completed

In the cooler morning (92 degF by the time I got to the carport), I went back to connecting the cables to the engine controls. And I immediately ran into an Oregonian Mystery. I followed the plans precisely and it was asking explicitly to re-use the locknut on the throttle arm that we had previously removed. It's the shiny, silvery nut in the picture.

Now this is a metric nut and I noticed that when tightening this nut, the bolt it was supposed to tighten was an imperial one (3/8" wrench). This worked for a bit until I tightened it a bit more and it turned pretty loosely all of a sudden. Also I had not noticed any resistance when I screwed it on and got to the locking section of the nut. 

Clearly this indicated that I had the wrong size nut and I just removed some of the threading (from the nut).

I tried an AN365-1032 stop nut and that went on with a much better feel and it tightened properly and the locking part worked as well.

I checked the instructions again and I could not find anything else than to re-use the metric Rotax stop nut. I think this is a mistake and I will post this in VAF later today. See the correct nut in the following picture.

The choke cable installation was pretty uneventful, just hard to get at on the right side for trimming it to the correct length.

Now, I just have to seal the grommet holes with firewall sealant or ProSeal and then I can mark this chapter finished.

I will let the RTV I used on the potential rubbing point between left throttle cable and oil hose for the pressure sensor settle and then tighten the double clamps that control the cables and also install the air filter on the left side.

Then it is back to finish left out steps. A lot will have to do with applying sealant which I would like to do all at once.

Cabling the Controls

I got home early today. Early enough to work a bit more on installing the engine controls. So I connected the cables to the engine and found a routing that should be causing minimum interference with sensitive parts like oil hoses and such. I also installed the slightly softer McFarlane springs on the throttle, replacing the Rotax original hardware.

It took me a bit to get this all set up because of not being able to find appropriate tools that would fit the hardware. I realized a bit late that this is metric hardware that caused me the troubles. Use a metric 10 wrench on the nuts of the throttle arm and a metric #4 allen wrench for removing the existing bolt attached to the throttle.
I have a slight interference between the left throttle cable and the oil hose leading to the pressure sensor and I will apply some RTV to it to avoid chafing.
After an hour I called it quits as it was a hot and slightly humid day that made working outside not very enjoyable. I will finish up tightening the hardware tomorrow morning.

The Mysterious Engine Log Book

Before I ventured deeper into the ways of acquiring a replacement fuel hose from a Rotax Service Center in response to the SB 912-061, I browsed the good ship VAF for the experience of others in this matter.
I remembered that I had read about this SB shortly after my engine had been delivered last year and I found it here.
The interesting information that I took away from it was that some had this SB been taken care of before their engine delivery by some licensed mechanic through Van's or maybe the Rotax distributor and that such action had been noted in the Rotax Engine Log Book that they had received with the engine.
That made me feel very uneasy as I had absolutely no recollection that I had ever seen such a log book along with the paperwork that came with my engine. Unfortunately, I was at work when I had learned about this and I had to actively fight the urge to run home and check if my log book was missing (a 20 miles drive - one way).
When I got home I went through the collected stack of papers related to the RV-12 and, sure enough, I found the log book. You can really easily mistake it as yet another Rotax instruction manual as the shape and the cover page looks just like the service and maintenance manuals.

So I had put this important log book away with all the other Rotax documentation and never looked at it again for about a year.
Now, that I had learned that there might actually be an important entry in this log book, I opened it and found - to my big relief - an entry on page 5:

And that said that the SB had already been complied with and that a fuel leak test would have to be performed once the engine was installed.

So, there you have it. That was an easy job this time to complete this Service Bulletin!

Controlling the Engine

I thought the next step was to finish the safety wiring on the gascolator but then I realized that I wanted to open the bowl and check for debris after the first engine run. I would have to cut that wire to remove the bowl and I think it is less than pure joy to put it on to begin with. So I decided to wait with the safety wiring until before certification day.

Instead of safety wiring I started on installing the engine controls, choke and throttle.

Sliding them into place was fairly easy to do. Getting those cushioned clamps in place was not. The help of some temporary tie wraps made this possible though.

Tightening the nuts on the back of the controls was again pretty awkward to get to. A wrench would hardly turn before it needed repositioning because of interference. This -12 is really hard to work on because of limited space. I sure hope this will all just stay in place forever.

Once everything was tightened down it looked pretty though and was well worth the effort (I guess that goes to say for the whole plane).

The firewall forward part had another surprise for me waiting. The job was to install a double clamp to keep the 4 cables from rubbing on any part of the motor mount. This thing put up quite a fight and I needed the help of tie wraps on both clamps and lot of creativity to get tools on both ends of the screw at the same time.
I think I probably worked half an hour on getting the nut installed on this double clamp alone.

I have not tightened it yet as I want to see how the attached ends of the cables affect the way they curve around the engine mount. Then it should be easy to finalize the position and tighten it.

So I first have to give these dangling cable ends a purpose before I can do this.

Oil Cooler Fits!

I was so concerned about my modification of the oil cooler position possibly causing problems when attaching it to the cowl and installing the cowl.
Those concerns were not warranted as it turned out that wit a slight modification of the routing of the right oil hose that attaches to the cooler, the system fit perfectly.

It first did not look so good though when I first tried to fit the cowl on. I installed the cooler guides on the bottom cowl as the first step.

In this picture you see the conventional routing of the right oil hose.

With a lot of pulling and cussing the cowl finally slipped into place (or better, yet, was forced to do so). That looked only good from the distance.

On the bottom curves though you could see that the cowl was under a lot of tension and pulled to the left (or pushed, as it later turned out).

So what was causing this? There is so little room in engine area that I could not take a picture of the interfere nor could I myself see it. Bending my arm in ludicrous ways to get my finger tips to follow the oil hoses and feeling for possible contacts, I finally found the reason. The fuel spillover line installed as a patch to the need of Rotax installing a different mechanical fuel pump that vents fuel overboard in case of a malfunction, prevented the oil line from moving up where the oil cooler wanted to go.
This might only be caused by me moving the oil cooler about 1.5" forward as I also had to move it slightly higher than initially planned for. But the clearance would be minimal (if any) in the original position as well.
The reason the oil line is interfering with the aluminum fuel vent line is that the oil line is pointing about  30 degrees toward outboards with the original routing and therefore crossing the vent line. I saw that if I could persuade the line to attach straight from the aft to the cooler, that the line would then clear the vent line and had a chance to bend out of the way further aft.
I tried a few approaches before I finally settled on this one:

The only problem I saw with this routing was that the lower water hose is pushed slightly towards the exhaust and could possibly touch the spring after a while. I planned to apply RTV between the spring and the hose in that area.
There is now only a minimal push to the left as you can see by the oil cooler mounting holes being just slightly out of position.

With this setup the cowling went on almost as easy as before without an oil cooler and there was practically no tension on the cowl.

Before taking the cowl off for the last touches on the lower engine installation, I thought I should take some more shots of this pile of aluminum that now looks almost like a plane...

My wife helped to get some shots of the interior with the cowl still on to give you an idea of how much clearance my modification gave me between oil cooler and muffler.

You'll be the judge as to how vital this modification has been. Without the distance I moved this forward, I could have just squeezed a finger between the cooler and the muffler.

Once the cowl was off again, I finished section 48 (Muffler Installation) by filling the springs with RTV. While at it, I also applied some extra RTV between one of the right springs and the water hose to prevent it from getting contact.

Now this had to cure and so I decided to go back inside and escape the 100 degF it had reached in the carport by then.
I cannot find the description for the next step but I know that the screws holding the bowl to the gascolator have to get safety wired. So I will do that next and then install the bottom cowl and leave it on.
The next section is the installation of the engine controls and after that I could install the tank and fire the thing up.