intermittent problem with Rotax 582

It does sound like a fuel problem.  What fuel are you burning?  Are your filters clean?  Is your fuel tank vented?  Is there anything in the fuel line other than the fuel pump you have changed, that could be restricting the fuel flow? 

I only use alcohol-free 87 octane automotive fuel.  There is some crud in the fuel filter, I am investigating that.  Tank is vented.  I have had problems with leaks in the fiberglass fuel tank and at one point when it was off for repairs emptied a lot of crud out of it, like fiberglass that had flaked off from the inside, so possibly I have clogs in the system.  I can direct the output of the electric pump into a tank and do a test to see what the fuel rate through the electric pump part of the system is and compare that to my engine burn rate.

I don't know much about carburetors, is there any carburetor failure mode that would look like what I have described?

Something to consider is that the seals may have dried out while it was sitting unused and you are now getting an air leak at high power settings. The engine is drawing in air through the crankcase seals causing a lean mixture which you were able to compensate for with primer. At a lower power setting less outside air would bypass the carbs. Now that the seals have had some oil on them they're probably a bit better but as you found with a passenger high power settings are still a problem.

This is a common occurrence among two stroke engines that are not used regularly. UPAC has a thread on this http://www.upac.ca/forum/showthread.php?t=36

The cost to disassemble the engine and replace the seals isn't really expensive. I don't know how many hours on the engine to know if it's due for a rebuild anyway. I would probably want to consider replacing the rotary valve shaft and seal. Some coolants cause deposits on the shaft causing the seal to leak. Coolant gets into the rotary valve oil and the centre bearings causing them to self destruct. The rattling sound is really unnerving to your passenger (ask me how I know).

http://www.kodiakbs.com/ has some excellent PDF's that show the engine broken down by individual parts which will help you decide whether to tackle this yourself or have a Rotax shop do it. A couple special tools are required.

Some other things you might also want to check

1. New plugs - i replaced mine every 10 hours with NGK BR8ES or B8ES depending on what plug caps you use.

2. Did the carb sit with fuel and get gummed up. I don't think this is a common problem with Bing carbs.

3. I'm assuming that you left oil injection installed but was there any moisture in the oil or was the first batch gummy?

4. Is the rotary valve oil clear with no milkiness. By now if the rotary valve seal was leaking you should see some evidence of milky oil in the rotary valve reservoir.

Have you checked you ignition coil? Occasionally a magneto or ordinary ignition coil will experiece a microscopic dielectric breakdown that is only evident when the engine is operating at maximum temperature. Characteristic of thermal cycling fatigue. As soon as the engine cools a little the coil retrurns to normal operation. If you have a way to static load the engine until it approaches maximum operating temperature, and if it starts to miss, or cut out, try carefully pouring cold water directly onto the coil or magneto, whichever you have. Be careful the water does not run over hot engine parts. If you are not comfortable doing that try laying a wet cloth over the coil that has been soaked in ice waer and see if the engine begins to run normally. If it does its a sure sign you have a defective coil. Of course an even better method is to substitute a coil or magneto from a known good engine and repeat the same operating procedure that caused the engine to miss. Have seen this phenomenon on a Continental C65, a VW engine, an old Chevrolet straight six from the 50's and on a restored 1948 Indian motorcycle. Each time mag replacment or coil replacement cured the problem. Hope that helps.  The Indian was the easy one. NAPA stores still sell the automotive ignition coils those old Indians used.

Randall Reihing

Based on your first post and this one, you are describing the exact same thing that happened to me a few years ago. I had repaired the fiberglas tank and the original small finger strainer in the tank became partially clogged with fiberglas dust in spite of my efforts to rinse the tank. The 582 ran fine at cruise power but surged badly at full power, and the electric fuel pump only helped a little. Ended up taking the old strainer/pickup out of the tank and replacing it with an automotive type nylon fine mesh finger strainer that was bigger around than my index finger and half again as long. Got it at Advance for a few bucks and no more problems.

Since you say you are running the pulse pump and the electric pump in parallel you may have to modify this, but here's how to check if clogging is the problem: I run my fuel pumps in series with the electric pump below the tank and the pulse pump up near the engine, so I disconnected the fuel line just downstream of the pulse pump and added enough line to remote it to a bucket or jug. Turn on the electric pump and check for flow, mine was marginal, and that's how I knew the problem was a clog at the pickup.

Since then my theory is that you cannot have too much surface area on your finger strainer if you are using a fiberglas tank that you have worked on, and the auto parts stores sell them too cheap not to -  especially since most of those strainers are designed for a 1/4" line, and there is a plethora of them out there. Just ask for one that goes down in an automobile gas tank, and they will eventually find you something that fits a 1/4" tube. Would give you the part number for the one that I am using, but I didn't write it down -

Hope this helps.

rp

Thanks, I'm pretty sure clogged fuel line is the problem.  I ran my electric pump into a receiving tank last night (through the fuel filter etc) and it took almost 20 minutes to get 2 gallons, which is 6 gal/hr, I use 5.5 gal/hr average with 2 on board so this would not be enough fuel to support climb power.

Bob - I'd recommend that you test your fuel very closely and carefully also.  Some fuels do have ethenol in them even though advertised as ethonol free.  Ethonol has been known to do a job on plastic fuel tanks - it actually desolves some plastics and this desolved material clogs fuel lines and filters. 

I do test my fuel, but I don't know what the original owner may have used.

Richard when you repaired your fiberglass tank had you used alcohol in it?  I'm beginning to think that maybe my original problem is that the previous owner used fuel with alcohol, which attacked the tank and caused the leaks that I had to repair as well as the debris in the tank from disintegrating fiberglass.

First thing i would do is get me a plastic tank. If alcohol fuel has ever been used the fiberglass is gone continue to break down and cause trouble. If using the primer makes it run better you definately have a fuel problem, no electrical problem. Your carb jets are probably gummed up from old gas. The carb jets needs to be cleaned or replaced.

Where can I get a plastic tank for a powrachute?

Thanks to all who have offered comments.  I believe the root cause of my problems was alcoholic fuel that had been stored in the fiberglass fuel tank before I bought the machine last fall.  The alcohol dissolved the fiberglass resin, which caused several leaks that had to be repaired shortly after I bought it and also created debris in the tank from disintegrating fiberglass.  The debris clogged the filter.  I replaced the fuel pump after trouble on my first 2 flights and thought I had fixed the problem, but what really fixed it was the fact that I replaced the fuel filter at the same time.  After 16 hours of flight the debris from the tank had clogged the new fuel filter, restricting fuel flow, which caused the engine to cut out at high power settings.  I am going to replace the fiberglass tank with an aluminum tank which otter solve the problem.

Glad you solved your problem.  If it is any consolation, you are not the first to have this happen (and, unfortunately, you probably won't be the last)