rotax 582 carburettor? problem

[robinsm]

I am close to tearing out what little hair I have left. I am running a grey head rotax 582. I bought the motor second hand. It had been reconditioned and I hasten to add that I have found nothing mechanically wrong with this engine. (The problems I have had I believe are related to my inexperience.) The problems I have had all seem to be related to fuel problems. I have cleaned the fuel system out (I didn't clean it out when I filled it with fuel for the first time. I have fixed vacuum leaks, fuel fitting leaks and a faulty curtis valve (it leaked). I have just cleaned the carburettors out and checked the needles and jets. I fixed one carby, (I had put the needle on top of the plastic thing instead of under it).

 

Thinking I had cured the problem, I ran the engine up on the ground and it went well. I took off this morning and did a low level circuit and it ran well. Touched, applied full throttle for the take off, got to about 150 ft and the ****** thing started running on one cylinder only. Luckily I had selected the longest runway for the test and was able to put it down on the tarmac. Parked, ran the motor up for a short run and it ran fine so I taxied out and took off. Well needless to say at 150ft the damn thing dropped back to one cylinder again. Took the hint this time and taxied back to the hanger. Secured the tail of the aircraft to a post and ran the engine up to 6000 revs outside the hanger. About 30 secs into the test I saw one of the egt needles (I run a dual needle gauge) go to zero and the engine began to run on one cylinder again. (checked the gauge, both needles operating correctly). I am guessing that fuel starvation to one cylinder cased the problem. What should I be looking for and what level should the petrol be in the carburettor bowl? Will a low bowl level cause this problem.? All and any suggestions greatfully received as I want to fix this so I can go and play with the clouds.

 

Thanks

 

Maynard

 

 

[Guest High Plains Drifter]

Maynard,

 

What was the temperature and humidity at the time, and was the petrol from your regular servo ?

 

From your EGT could you tell which pot failed ?

 

Engine on an X-air ?

 

HPD

 

 

[eastmeg2]

Maynard,

 

That sounds exectly like a problem a friend of mine had with an older trike a few years back. It also ran a silvertop 582.

 

If it was not so serious it would have been funny to watch his trike reach 100ft AGL, loose power and start descending, then he'd squeeze his fuel primer bulb, briefly get power back and start going up again, then down again, etc, etc. His engine also ran flawlessly in ground test runs.

 

I think I remember it being that the circlips on his carburettor needles were in the wrong position by one groove.

 

I have taken the liberty to email the text from your first post in this thread to him for his feedback and am trying to entice him to come to the Goulburn airport BBQ again on 22nd Dec.

 

He's also a self employed mechanic.

 

Cheers,

 

Glen

 

 

[eastmeg2]

Also, what temperatures are your EGT's reaching? Should be somewhere between 1100-1200F with the 582. A short ground run at 4000rpm should give you a good reading, just don't do it for too long, or risk overheating your motor.

 

 

[thommo]

Mate have you got a picture of how the carbs are on the engine.The other ting to do is put a fuel pressure gauge on it and run it and see what it does.

 

 

[facthunter]

Carbs.

 

Robinsm, Take the aircleaner off, open the throttle fully and with your delicate little fingers (if you have them) or otherwise a pair of long nosed pliers wrapped with tape to prevent damage, see if you can move the needles up or down . ( Check the operation of the clips) Nev..

 

 

[eastmeg2]

My mates reply to the text from your first post:

 

"Yes All of the above and I had to replace the stator as they have a low current problem under high load operation."

 

Rgds,

 

Glen

 

 

[jetboy]

Have you replaced the viton tipped float needle valves ? These loose their ability to shut off the float fuel supply from the engine suction pump at high rpms, due to fuels attacking the rubber. They are very hard to check visually. New ones look the same but work properly. If you have this problem, a ground run at high power with observer might see fuel coming out the plastic overflow tubes. But the EGT usually just gets low and engine " bogs down" with overrich mixture. If your EGT is dropping straight to zero, might be a blockage in the float or jets.

 

Ralph

 

 

[robinsm]

Thanks for the replies and ideas.

 

1 - Temperature about 28c. Humidity 30% (normal for this time of year in Goulburn.)

 

Petrol from normal supplier and premixed by me as per my standard procedure. I think it was the front pot that failed from the EGT but subject to checking. Engine is mounted on my Xair standard as per the avatar photo. Carburettors are mounted perpendicular to the motor, not the ground so they are level when aloft.

 

2 - Unfortunately using the secondary Facet fuel pump made no difference when the problem occurred (runs correctly - checked). Good point about the position of the circlips on the needle valve thanks, will check that. The stator generates correctly when under load, no problem there.

 

3 - Needle valves are able to be moved and move up and down when the throttle is operated. Fuel pressure needs to be measured but flow seems fine when measured into a jug.

 

4 - Because the EGT for the cylinder dropped to zero I am going to have to check for blockages (again). The viton tipped valves may be sticking, I will have change them.

 

Thanks for all the great suggestions, it gives me a real good flying start at this thing.

 

Thanks

 

Maynard

 

 

[robinsm]

Update:

 

Removed the Carburettors, striped them down and really cleaned them and the system out. Discovered major blockage of the intake valve with peices of the sealant I used on the brass fuel fittings. How it got through the filter I don't know. Reassembled both carbs, checked the mikuni pump for peices of garbage and installed both back on the rotax 582 (grey head).

 

Today, went out to the airport, started the xair and it ran ok. Did half a dozen circuits and it didn't miss a beat. (whew!!!!!!). My next questions are:

 

1 - Even when I wind the idle screw right in, the engine only idles at about 1800 rpm.??

 

2 - On a 4 slot needle valve, where should I be putting the clip, all the data I have applies to 3 slot needles.

 

3 - When on cruise at 5500 rpm, EGT only at 1050 degrees. Is it running to rich.

 

4 - Engine will only rev out to 6000 rpm. I run a brolga 3 blade prop as recommended for this aircraft. (xair std).

 

The amount of knowledge on this forum is great. Thanks for your help.

 

Maynard