Rotax 914 carbureted issues!

[GyrOZprey]

An owner with a 914 stock engine discovered THiS -after standard maintenance replacing fuel lines after aged leak issues! And also rebuilt the carbies!

“OK gang, here are the details on my Rotax 914 fuel repair. (Will keep these to a minimum but thought I would like to share some valuable information)
a few weeks back, prior to flying, Thomas and I discovered SEVERAL severe fuel leaks from BOTH the feed and return lines of my fuel system. Ordered heavy duty 225 psi barricade fuel line and replaced same.
Here's where it gets to the perplexing point. Rick Grenfeld who is a fellow trike pilot and Rotax heavy mechanic, helped me to rebuild my carburetors with new rubber O-rings and gaskets. The gaskets that were sent to us were rubber. According to the Rotax torque specifications, you're to replace the gaskets and re-torgue the bottom of the carburetor float bowl to 40" pounds. After reassembling the carburetors and attempting to do a run up, we could only get 3000 RP M's from the engine before it started to bog down. We spent most of the day toying with this perplexing issue to no avail. The following day, I contacted specialist at leading edge airfoils, who then advised that there is an advisory specifically on the 914 engine stating that rubber gaskets cannot be used. The paper gaskets must be either reused or replaced. The specifications on the torque of that float bowl with the paper gaskets should only be 25" pounds.
We were able to reassemble both carburetors and fire up the engine and sync the carbs. We were able to achieve full power again on the machine, so all is well with the engine. And yes, I did take down the fuel gascolator. I was very surprised at the amount of debris in the float bowl and what I found in the screen as well. That was thoroughly cleaned and replaced as well. Another quick FYI, Bing carburetors are no longer providing paper gaskets for the Bing 64 carburetor system so as an owner, you'll have to pre-fabricate paper gaskets to suit the 914 turbo platform.
Apparently, Rotax Aircraft corporation is aware of this situation and has washed their hands of this information and is pl
acing the responsibility on the owners as well.
Have not had the opportunity to fly since the total repair as we have poor flying conditions but hope to do so tomorrow afternoon. This has been a very good education for me as far as the fuel system is concerned. Just a heads up for the gyro community.
As always, fly well and safe.”

We have had quite the discussion on our TAG owners forum - the expert consensus seems to be IF carbies are not giving any trouble LEAVE THEM ALONE!! -last resort troubleshoot for fuel/ power issues!

 

[Abid]

An owner with a 914 stock engine discovered THiS -after standard maintenance replacing fuel lines after aged leak issues! And also rebuilt the carbies!

“OK gang, here are the details on my Rotax 914 fuel repair. (Will keep these to a minimum but thought I would like to share some valuable information)
a few weeks back, prior to flying, Thomas and I discovered SEVERAL severe fuel leaks from BOTH the feed and return lines of my fuel system. Ordered heavy duty 225 psi barricade fuel line and replaced same.
Here's where it gets to the perplexing point. Rick Grenfeld who is a fellow trike pilot and Rotax heavy mechanic, helped me to rebuild my carburetors with new rubber O-rings and gaskets. The gaskets that were sent to us were rubber. According to the Rotax torque specifications, you're to replace the gaskets and re-torgue the bottom of the carburetor float bowl to 40" pounds. After reassembling the carburetors and attempting to do a run up, we could only get 3000 RP M's from the engine before it started to bog down. We spent most of the day toying with this perplexing issue to no avail. The following day, I contacted specialist at leading edge airfoils, who then advised that there is an advisory specifically on the 914 engine stating that rubber gaskets cannot be used. The paper gaskets must be either reused or replaced. The specifications on the torque of that float bowl with the paper gaskets should only be 25" pounds.
We were able to reassemble both carburetors and fire up the engine and sync the carbs. We were able to achieve full power again on the machine, so all is well with the engine. And yes, I did take down the fuel gascolator. I was very surprised at the amount of debris in the float bowl and what I found in the screen as well. That was thoroughly cleaned and replaced as well. Another quick FYI, Bing carburetors are no longer providing paper gaskets for the Bing 64 carburetor system so as an owner, you'll have to pre-fabricate paper gaskets to suit the 914 turbo platform.
Apparently, Rotax Aircraft corporation is aware of this situation and has washed their hands of this information and is pl
acing the responsibility on the owners as well.
Have not had the opportunity to fly since the total repair as we have poor flying conditions but hope to do so tomorrow afternoon. This has been a very good education for me as far as the fuel system is concerned. Just a heads up for the gyro community.
As always, fly well and safe.”

We have had quite the discussion on our TAG owners forum - the expert consensus seems to be IF carbies are not giving any trouble LEAVE THEM ALONE!! -last resort troubleshoot for fuel/ power issues!

How old was the fuel line and was it rated for E10 fuel. I am surprised that you had leaking cracked fuel line.
I would advise using E10 compatible fuel line. One of the better fuel lines would be Aeroquip like this one

https://www.speedwaymotors.com/Aeroquip-Special-Application-Socketless-6-AN-Hose-Black,279119.html?sku=617006-3&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQjwmN2iBhCrARIsAG_G2i4-YbXZ8o-R7_V9ydqS-c1Fq60pnx_UAnuffRfJeECvdbPnQEQn6qAaAtlvEALw_wcB

Should last many years.
Yeah do not go by torque spec on that carb bowl. Just slightly tighten it to 24 inch pounds and run the engine and check if there is any leak. If there is tighten a touch more and when it stops leaking, leave it alone and safety wire the bolt.

 

[GyrOZprey]

The aircraft had spent several years in Arizona ...a climate that proved VERY HARD on all rubber parts!

 

[MikeBoyette]

I wonder if that affects the rate of unplanned pregnancies there? . Sorry I couldn’t resist.

 

[Abid]

The aircraft had spent several years in Arizona ...a climate that proved VERY HARD on all rubber parts!

No worse than New Mexico I would think. Aeroquip hose will hold up

 

[WaspAir]

Southwestern dryness is good for just about everything on an aircraft. It's intense UV exposure (high elevations and clear skies) that is tough on the flexible bits (and the paint), and covers or hangars provide the answer to that.

 

[okikuma]

We have had quite the discussion on our TAG owners forum - the expert consensus seems to be IF carbies are not giving any trouble LEAVE THEM ALONE!! -last resort troubleshoot for fuel/ power issues!

I cannot even begin to count from my old hotrodding past how many times someone had experienced poor performance due to rebuilding a perfectly healthy and operating carburetor.

Wayne

 

[MikeBoyette]

I cannot even begin to count from my old hotrodding past how many times someone had experienced poor performance due to rebuilding a perfectly healthy and operating carburetor.

Wayne

Well Rotax does things that puzzle me. Turbo through the carb that is not designed to be pressurized. Discover that it causes leaks the solution then is to put a cup to catch the leak and drain just an above the hot exhaust manifold. This was easier than just building a fuel injected engine from the start? The excuse that fuel injection is complicated, doesn’t hold water with me either. Rotax acts like fuel injection of some kind a new technology. Last I checked Tucker had it in his cars in the 1940s or 50s. Hell I even think the lawnmowers are now fuel injected. Most engine manufactures even Briggs & Stratton used as a forged crank. Why Rotax still insists on building crankshaft for four strokes like their two strokes is beyond me. Still blows my mind to pay $30,000 for an engine that uses ancient technology. They are one of the biggest reasons general avaiation is in a decline. Hard to build an affordable aircraft when your engine takes up half to 3/4 of the cost of the total machine. It basically boils down to they have a monopoly they know it and they’re going to continue to take advantage

 

[Abid]

Well Rotax does things that puzzle me. Turbo through the carb that is not designed to be pressurized. Discover that it causes leaks the solution then is to put a cup to catch the leak and drain just an above the hot exhaust manifold. This was easier than just building a fuel injected engine from the start? The excuse that if you injection was complicated, doesn’t hold water with me either. Rotax acts like fuel injection of some kind a new technology. Last I checked Tucker had it in his cars in the 1940s or 50s. Hell I even think the lawnmowers are now if you injected. Most engine manufactures even Briggs & Stratton used as a forged crank. Why Rohtak still insists on building crankshaft for four strokes like their two strokes is beyond me. Still blows my mind to pay $30,000 for an engine that uses ancient technology. They are one of the biggest reasons general avaiation is in a decline. Hard to build an affordable aircraft when your engine takes up half to 3/4 of the cost of the total machine. It basically boils down to they have a monopoly they know it and they’re going to continue to take advantage

Mike it is not like that. Rotax is making a production certified aircraft engine. Meaning 914UL is available in EASA and FAA certified form as well. They need both design and production certification. Fuel injection module suppliers at the time 914 was released would have to subject themselves to EASA and FAA production system audits whenever FAA or EASA wanted to do them. Liability in aircraft engines is a ton lot more than car engines and volume compared to cars and motorcycles is tiny. Very few if any vendors want to be in that supply chain and those who do agree charge a bundle. Low volume, high liability, extremely strict audits of the whole production and QA system and documentation. That is why everything aircraft specific is expensive. Car engines are made in 100,000 multiples. The ECU for Rotax iS engines is supplied by Honeywell who are about the only vendor willing to deal with aircraft and the ECU costs $8000. That was not a viable option in the mid 90's when 912 and 914 came out.

A lot of pilots of certified aircraft preferred (at the time) and many of them still prefer carb engines.
Oh and 914 now costs (as of March 1, 2023) $36500, not $30k.
They have increased its cost more than any other engine. Rumors are they have limited supply left of TCU for 914 and they plan to sunset it and want people to buy more 915 and 916

 

[okikuma]

Well Rotax does things that puzzle me. Turbo through the carb that is not designed to be pressurized. Discover that it causes leaks the solution then is to put a cup to catch the leak and drain just an above the hot exhaust manifold. This was easier than just building a fuel injected engine from the start? The excuse that if you injection was complicated, doesn’t hold water with me either. Rotax acts like fuel injection of some kind a new technology. Last I checked Tucker had it in his cars in the 1940s or 50s. Hell I even think the lawnmowers are now if you injected. Most engine manufactures even Briggs & Stratton used as a forged crank. Why Rohtak still insists on building crankshaft for four strokes like their two strokes is beyond me. Still blows my mind to pay $30,000 for an engine that uses ancient technology. They are one of the biggest reasons general avaiation is in a decline. Hard to build an affordable aircraft when your engine takes up half to 3/4 of the cost of the total machine. It basically boils down to they have a monopoly they know it and they’re going to continue to take advantage

Until the Chinese Zongshen Rotax copies regularly experience TBOs greater than 1500 hrs.

Wayne

 

[Abid]

Until the Chinese Zongshen Rotax copies regularly experience TBOs greater than 1500 hrs.

Wayne

It is probably a decent engine but I do not think western markets are ready to trust a Chinese copy yet. Chicken and egg problem

 

[okikuma]

It is probably a decent engine but I do not think western markets are ready to trust a Chinese copy yet. Chicken and egg problem

Only time in service will tell. The same when Rotax 900 series were first introduced in the USA.

Wayne

 

[loftus]

I think finally Rotax are starting to leave carb engines behind, Zongshen should do the same. They could offer a fuel injected alternative at a fraction of the cost of the Rotax is engines. I have over 75 hours now on my Edge Performance EFI conversions and couldn't be happier. Average fuel consumption flying around between 60-80 mph is about 2.6gph per engine. Quieter, smoother, easier start, better fuel consumption, maybe a little more power. What's not to like about fuel injection.

 

[nishanh]

I think finally Rotax are starting to leave carb engines behind, Zongshen should do the same. They could offer a fuel injected alternative at a fraction of the cost of the Rotax is engines. I have over 75 hours now on my Edge Performance EFI conversions and couldn't be happier. Average fuel consumption flying around between 60-80 mph is about 2.6gph per engine. Quieter, smoother, easier start, better fuel consumption, maybe a little more power. What's not to like about fuel injection.

Where did you get this mod done? Or did you do it yourself? The only USA dealer I see is in Kansas.

 

[loftus]

Where did you get this mod done? Or did you do it yourself? The only USA dealer I see is in Kansas.

I did it myself - there are two dealers in the US I believe. I bought mine from Michael Busenitz, STOL Creek Aviation in KS.

 

[Aaron R]

What's not to like about fuel injection.

I generally agree, except when restarting a hot motor after fueling at the island, with pilots waiting for me to get out of the way. Embarrassing that it takes me 3-4 start attempts.

 

[loftus]

I generally agree, except when restarting a hot motor after fueling at the island, with pilots waiting for me to get out of the way. Embarrassing that it takes me 3-4 start attempts.

Hot starts are not an issue in my experience with the Rotax 912 and Edge EFI

 

[GyrOZprey]

I'm enjoying my 914 upgrade with EDGE FI & intercooler (+aux alternater kit) from STOL Creek Aviation ...US Edge dealer Michael Busenitz ...just 4 miles south of my place!!!
smooth low idle , smooth running engine ...fuel savings, much simplified TCU & smooth linear turbo-power! - and no more stink'n carb float(recalls) & yearly balance & synch jobs!