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Roger Lee

Carb bowl obstruction - Don't be stranded

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Roger, I've cleaned my carb bowls twice (though I found virtually no contamination), cleaned the main jets once, and replaced the fuel and spark plugs but still the engine loses power at full throttle a couple hundred feet in the air. It runs fine on the ground at full throttle but I've lost power four times now. When I reduce power the engine again runs okay. Tom Baker did my hose replacements last September but the engine ran well for 30-some hours, including the trip to the Page fly-in.

My fuel pressure gauge was acting up at Page (fluctuating) so I disabled the warning buzzer. I replaced the sensor today and when I test ran the engine I got a steady fuel pressure indication barely in the yellow - about 2.5 psi. Do I need to purge the line of air or something after replacement? Or could I really have insufficient fuel pressure?

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You either have a bad or clogged fuel pump and need to put a mechanical gauge in line and double check the pressure. Plus the carbs need to come completely off and flush every orifice with cleaner and blow them out with air. Every orifice. You have a fuel flow problem. You can spend a ton of time and keep trouble shooting or just do the two items above.

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Just got an email from a Sportcruiser friend in TX.

You can reacue yourself and with any power loss the carbs should be the first place to check upon landing and then hopefully you get to continue your journey. See the first post in this thread if your new or don't remember. It seems to have saved several.

-–---–---------------------------------------------------------------------------------------------------------------------------------------------

"Hi Roger -

 

Pat yourself on the back, your recent youtube video on cleaning the carb bowls after a power loss saved my ass.

 

Was flying happy as a clam (actually I was taking my biannual flight review) when suddenly engine got rough and lost RPM. I immediately thought the instructor had pulled the throttle for a simulated emergency - but quickly discovered it was a real problem. If I reduced throttle to half it would smooth out. The most I could make was 4000 RPM. Cognizant of the rubber debris syndrome after a 5 year hose change and after going thru all the emergency procedures I confirmed that reducing throttle improved the situation while increasing throttle would lower the RPM (as the debris got sucked up against the carb jet).

 

Able to maintain 4000 RPM I advised Center I was diverting and easily made it to an airport 7 miles away. Having recently watched your youtube video as a refresher, I removed the carb bowls at my emergency landing airport and sure enough there were large rubber shavings in it. I cleaned the bowls, reassembled, test flew and then uneventfully was able to return to my home base with the engine not missing a beat."

 

Thanks,

Sportcruiser

Alpine, Tx

 

 

 

 

 

 

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:-) We run 4200 rpm as normal cruise in the UK / Europe if im flying with a friend in his skyranger at 80mph im running 0 flaps and 3600 rpm

 

Mike

 

 

 

Just got an email from a Sportcruiser friend in TX.

You can reacue yourself and with any power loss the carbs should be the first place to check upon landing and then hopefully you get to continue your journey. See the first post in this thread if your new or don't remember. It seems to have saved several.

-–---–---------------------------------------------------------------------------------------------------------------------------------------------

"Hi Roger -

 

Pat yourself on the back, your recent youtube video on cleaning the carb bowls after a power loss saved my ass.

 

Was flying happy as a clam (actually I was taking my biannual flight review) when suddenly engine got rough and lost RPM. I immediately thought the instructor had pulled the throttle for a simulated emergency - but quickly discovered it was a real problem. If I reduced throttle to half it would smooth out. The most I could make was 4000 RPM. Cognizant of the rubber debris syndrome after a 5 year hose change and after going thru all the emergency procedures I confirmed that reducing throttle improved the situation while increasing throttle would lower the RPM (as the debris got sucked up against the carb jet).

 

Able to maintain 4000 RPM I advised Center I was diverting and easily made it to an airport 7 miles away. Having recently watched your youtube video as a refresher, I removed the carb bowls at my emergency landing airport and sure enough there were large rubber shavings in it. I cleaned the bowls, reassembled, test flew and then uneventfully was able to return to my home base with the engine not missing a beat."

 

Thanks,

Sportcruiser

Alpine, Tx

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:) his Skyranger fly's at 80 mph cruise so i fly my ctsw at 80 mph he is using 4200 rpm i only need 3600rpm

 

after speaking with you before about engine speed i did a a poll of UK/and some Europe flyers all with varying aircraft with rotax 912/912s to see what rpm's they cruise at ALL are around 4200 rpm cruise and 5200 rpm flat out

 

Cheers Mike

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Hi Mike,

 

4200 cruise and 5200 flat out is against all our Rotax schooling here in the states. I'm supposed to go to a special Rotax school the first part of Sept. in Nassau so I'll be more direct in posing this question. It has been ask in every Rotax school I have been to and the answers have always been the same to stay away from these as a normal run perameter. Even aome of the SB's address this somewhat. I know some of the LSA Mfg's were warned away from the 5200 WOT issue years ago.

 

It won't hurt to ask again.

 

The answer has always been, it wasn't designed to run there and it causes too much internal vibration and stress.

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Well, we remember Phil Lockwood's EAA seminar from a few months ago in which he agreed with the book, not the more restrictive numbers we sometimes see.

 

I'd like to be at the class in Nassau to see how the question is phrased and the exact answer. I believe from what I have read that the boys in Europe are doing what Rotax says.

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It is a fuel injected class taught by Rotax. Only 6 people were invited.

I'm very thorough and I'll ask in several different ways. Documentation like batteries are not included. :)

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It depends on what I'm doing. In the shop and working is one thing. Out in the field is another. For a quick check of the bowls only this method is fine.

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It is a fuel injected class taught by Rotax. Only 6 people were invited.

I'm very thorough and I'll ask in several different ways. Documentation like batteries are not included. :)

 

One way to approach it would be to refer to the old ROAN document that listed 5,500 cruise as best practice. The doc said the 912ULS was designed to run its entire life at this RPM. It would be revealing to know where that came from and what was its basis.

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Easy answer.

 

From factory testing of thousands of hours and 20 plus years of experience.

 

And then the owner with ten hours contradicts that and always tells them they're wrong.

 

Hum, go figure.

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It is a fuel injected class taught by Rotax. Only 6 people were invited.

I'm very thorough and I'll ask in several different ways. Documentation like batteries are not included. :)

 

Glad to see that you were one of the invited to attend Roger. :)

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Yeah, well, ROAN is not Rotax, at least no one will admit to if officially. Rotax has numbers in print that have been argued about here before and I'm not going to reopen that argument, but if Roger comes back from Nassau saying that the book is wrong as he has been saying, I'd like to see some Rotax substantiation, not just Eric's repeated opinion.

 

Rotax has this secretive culture. It reminds me a lot of the Wizard of Oz or some arcane religion where only a few are allowed up on the mountain and they interpret for the rest of us since the great god Rotax doesn't talk anymore than it has to and then not enough to satisfy questions. It's the blind leading the halt, folks. It only gets by with it because it's a pretty good engine with a cult like following. God help Rotax if they had any real competition that was open and receptive.

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It don't think Rotax is secretive. It really boils down to a foreign company, translation from one language to another for manuals and other documentation, attending a real Rotax school at all the levels and seeing enough engines per year to get a handle on either what you have learned or how to diagnose issues. Learning what questions to ask and being a detailed oriented person. Sitting down and actually reading all the manuals (cover to cover) and bulletins. That said knowledge doesn't always make for a good diagnostician. For me it was something I learned in medical school and over 30 years of practice. For many it also comes down to money and time trying to attend a Rotax school. It cost to attend all these schools. This one coming up in Nassau is all out of my pocket. When all said and done I bet it will be close to $3-4K.

You have to go out and learn the info. It's there you just have to be willing to spend the time and look and ask questions. Learning an engine inside and out and what owners can do to that engine takes years. I constantly read and research info and that's what it takes. It's continuing education, just like the fire and medical service was for me.

 

 

I believe Eric has been with Rotax for approximately 30 years. If you ask him a straight question it has been my experience he'll give you a straight answer. Rotax and Eric have nothing to do with R.O.A.N.

Rotech is the main importer and testing facility for all of Canada and supplier for certified Rotax parts for North America.

Rotech - ROAN does a good job.

Kodiak in Nassau is the main import and Rotax testing sight for all engines entering the US.

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We have school aircraft here that have done 3000 + hrs that have had no major work or overhaul done to them and are still going strong so the lower rpms cant be that bad for the engine but this is only my opinion :>) i have been in the motor trade for 30 years and have attended several rotax courses here in the UK and flown over 2000 hrs behind Rotax

 

Mike

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Wow... 'good to know you are that kind of engine life.

 

I think we've covered this a few times.... It's not that lower rpms is "bad for the engine"... so much as lower rpms may cause vibrations and harmonics that's "not as good as" higher rpms. It's also possible that lower rpms may cause the engine to "lug", as it has much less torque and horsepower at, say, 4,000 rpm. Running at a lower RPM shouldn't cause red-lights and warnings to go off, but it's not treating your engine any better than running at 5,400.

One things for sure... you save considerable fuel $$$ running at 4K!

tim

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FD doesn't always get their numbers right and copy out of the Rotax manual that info for 3 engines and don't know how to interpret which. Like an idle rpm of 1400. That is okay for an 912UL 80 HP and even then it is smoother and easier on the engine at 1600-1700, but absolutely wrong for the 912ULS 100 HP with a compression of 10.8:1.

FD also messed up in the first years setting the WOT for 5200 rpm. They are not always right. The numbers in their manuals can use some updating.

 

I always tell people when you read the manuals you need to know which numbers go to which engine and unless you have some training or read all the manuals from cover to cover you don't always know or get it right.

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It always comes back to the assertion that there is a priesthood - the anointed ones - the cognoscenti - who are to be trusted even above the Rotax written word. I am willing to bet that if push came to shove Rotax would say - what did the book say?

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My two cents.

I have no problem with continuing ed and am signed up for the Rotax Line course at LEAF in Sept. What I don't understand is why something as basic as an RPM setting is not made clear by Rotax. You shouldn't have to read (and I suspect it would also take memorization) all of the manuals to get one RPM. I suppose we should be glad the manuals are not produced like the pidgeon English versions of other foreign assembly manuals - Rotax and FD could certainly find people to do these translations. Specifics should be indexed.

 

Besides that, Roger, you seem to be saying that we all need to have the same amount of experience as you in order to know enough. For most of us that is not going to happen.

 

I appreciate your willingness to be a resource, Roger, but if Rotax (and FD for that matter) would put out documentation that was clear and concise I wouldn't need to bother you so often. :) I will never catch up to you in the experience area. I do have the desire to be safe and to do things correctly. (Thus the phone calls.)

 

I would add that I believe Rotax has now created an engine that I will not have because of the extra cost (specialized equipment only available from Rotax) and the near impossibility of joining the exclusive group of repairmen. This will eventually make sales of the engine decrease. There really is no reason for this. The tech on this engine is not beyond what exists in modern automobiles. If the manuals and information on the engine were put out, there would be ways of duplicating the instrumentation and methods.

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I'm going to jump up on my soapbox a little,

 

 

I'm happy to help anyone at anytime. I take phone calls from 0800 to 2200 hrs. 7 days a week from all over the world. If people want the help no problem, it makes me feel good when I can help someone solve a problem. If your just going to give me a hard time and tell me Rotax or FD doesn't know what they are talking about then maybe that person should have spent more time doing his own research and not berate me for for taking the time and trying to learn more to do a better job and become better educated. I have some that always demand documentation from me. I'm not a secretary or an assistant and those questions and complaints are better directed at Rotax and FD direct.

 

 

No secrets. There never has been. You have to go to school, that's how all the better informed technicians of any profession learn. It will only cost you time and money. All the Rotax techs spent their time and money for their education and to get technical questions answered. Take the three courses and ask all your questions. Then get in and get your hands dirty and see 15-30 planes a year so you can see enough and get the experience and then you'll have all your answers. You can't possibly take one class and work on one plane that will give you all the answers you seek. I call Rotax myself if and when I get stumped. Talk to the right people and ask them the questions. Research on the web, a lot can be found there.

There is no other way around it and no company can ever publish everything about a complicated system so everyone would understand it without some sort of training from someone. This is the same reason we all went to school from 1-12 grades.

 

How many mechanics in the aircraft, motorcycle, boating or auto industry knew all that they know just by never taking a class or doing the research or having had someone else teach them. Who here that isn't a doctor knows what he knows. It took him years of training a practice and we go and listen to them and allow them to diagnose and treat us and we know almost nothing many times. Our entire existence is setup that way.

 

It's all out there for the discovery, but trying to learn it all without climbing outside the box won't happen. How many here have read all 5 of the Rotax manuals cover to cover? That is accessible right on the web and most questions can be answered there. It was the first thing I did when I got out of my first Rotax school. I figured my first Rotax school was like graduating first grade and I had a long way to go.

 

"Besides that, Roger, you seem to be saying that we all need to have the same amount of experience as you in order to know enough. For most of us that is not going to happen."

 

This may be true, but there is nothing I can do about it. It isn't my fault. Don't shoot the messenger. If you can't do all the above then you'll have to trust the techs, but if you don't then don't knock them, they're trying to help people and usually for free.

 

The Techs didn't know once upon a time either, but they all took the time to learn and it took years, not days, weeks or months.

 

I don't hear anyone hear knocking the motorcycle Mfgs or the auto Mfg's and they do the same thing. How about your TV sets. Who here could tell me everything about the internals on your Smart TV set and exactly how it works and how to test all the components. How many of you got a complete set of pictures of all the wiring and plumbing in your home before the walls were covered. Shame on the builder. How many of you could build a home from scratch without any help from the outside. If you ever had to get permits for a home or building what did you know before you started the first time and then did you know every thing there is to know about permits and inspections after it was all done.

 

It isn't just Rotax or FD, it's everyone and every where. You have to be willing to invest all the time it takes to know. You have to specialize these days.

 

Society has become a lot more complicated and specialized in the last century and you can't do it all. We need specialist. It's just life. I have to abide by and listen to other specialist myself in other fields.

 

We do what we can with what we have to work within a certain system. If that doesn't work then it's time to go to the source and work to get it fixed. Maybe it's time for everyone here to send emails to Rotax and FD?

 

I can try to help each person that wants help, but I can't fix the system.

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Sorry about the flak Roger :>) i hadn't intended to start an argument i was just trying to find out why you guys i the US are running your engines close to flat out in the cruise when it appears that most other places are around 4200 rpm mabe its because your fuel is so cheap :>) its $2 a ltr $10 a gallon here in the UK

 

Mike

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