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During climb out yesterday with my Thruster TST / Rotax 503 my RPM dropped and the engine began to run rough. I worked the throttle a bit and it was possible to run the engine at 5000RPM. I turned back to the field but shortly after I completed the turn, the power came back. So I decided to circle around the field until sunset and the engine ran without any problems during this time. The temperature was 12°C and the dew point was 11°C, so this made me believe it was carburetor icing. What do you guys think?

 

 

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During climb out yesterday with my Thruster TST / Rotax 503 my RPM dropped and the engine began to run rough. I worked the throttle a bit and it was possible to run the engine at 5000RPM. I turned back to the field but shortly after I completed the turn, the power came back. So I decided to circle around the field until sunset and the engine ran without any problems during this time. The temperature was 12°C and the dew point was 11°C, so this made me believe it was carburetor icing. What do you guys think?

Yes you can get carby ice in a two stroke..... I have had it! And with that due point spread, it is more than possible that was what you had.

 

But if you are worried that it might have been something else, pull the exhaust manifold off and have a look at the pistons, rings and cylinders.

 

Kiwi

 

 

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Yes you can get carby ice in a two stroke..... I have had it! And with that due point spread, it is more than possible that was what you had.But if you are worried that it might have been something else, pull the exhaust manifold off and have a look at the pistons, rings and cylinders.

 

Kiwi

Thanks for your reply!

It has good compression and the pistons, rings and cylinders looked all good and the engine runs just fine, so it was probably carb ice

 

 

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Just check for water or rubbish in the bottom of the carb bowl as well, higher throttle openings can suck up blockages that don't happen otherwise. Plugs and leads can also only show up under higher loads.

 

 

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Hi Capillatus.

 

I also fly a TST, how long have you had yours?

 

I've had mine about 12 months, and in the air for 3 now, I'm enjoying the basic flying a great deal.

 

I'm yet to experience carb icing in it but good of you to share.

 

Xy

 

 

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I wish you blokes would throw your Gillette razors away and use Okham's.

 

Dew point 11C; OAT 12C. You wouldn't have to go very high to get into icing conditions. That's the simplest reason for the power loss, and therefore the best.

 

 

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It could have been carb ice, but if reducing throttle stopped it I would look for a fuel problem. My experience is that carb ice is far more likely at partial throttle settings. I had it in a Thruster with a 503 engine and rather than fly over tiger country, I landed in a paddock next door to my home.

 

Took the plane home and removed the exhaust and looked in, sure enough the bore had tramlines so I did a proper teardown and found the bores just fine. the tramlines were an optical illusion. I had been told by the self appointed Thruster guru Tony Hayes that my bores were damaged. He had also been fooled by looking in the ports.

 

 

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  • 3 weeks later...

The problem was not due to carb ice.

 

The engine decided to die for me this weekend immediately after take-off, I still had about 200m of field in front of me so it was no problem to put down the Thruster safely. Once on the ground, the engine started on the first pull and idled smoothly, but as soon as I increased the throttle the engine died. I started to suspect fuel flow restriction so I opened the float bowls and the gasoline levels were very low. I switched on the electric fuel pump while the float bowls were removed and it was barely dripping any gasoline. So I changed the fuel hoses and the filter. The fuel flow now seemed to be in order, I started the engine and did some static tests. Everything looked good, but suddenly the engine stopped again. After some searching, I finally found the blockage, it was a loose piece of rubber inside the mechanical fuel pump.

 

 

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The problem was not due to carb ice. . After some searching, I finally found the blockage, it was a loose piece of rubber inside the mechanical fuel pump.

Well, I was wrong to claim atmospheric conditions, but the principle still holds - the simplest cause is probably the real cause. I bet you danced a jig when you solved the problem.

 

 

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Well, I was wrong to claim atmospheric conditions, but the principle still holds - the simplest cause is probably the real cause. I bet you danced a jig when you solved the problem.

Yep, it was nice to find the problem :)

The day before, I crossed Gulf of Bothnia twice when I visited some friends in Finland. It is approximately 50nm over open water and a total of 98nm between the fields. So I'm probably lucky that the piece of rubber didn't mess with me on that trip.

 

 

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Do you know where it came from?

 

Was it a part of the fuel hose?

 

It would pay to work it out as it may be the start of some deterioration somewhere in the fuel system.

 

 

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Do you know where it came from?Was it a part of the fuel hose?

 

It would pay to work it out as it may be the start of some deterioration somewhere in the fuel system.

It looked like a bit from the fuel hose.

 

I switched all the fuel hoses when I was looking for the problem so hopefully it should not happen again

 

 

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