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rotax brp

 

Engine cuts out after 20 min run.

  • Cody Evans
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2 years 5 months ago - 2 years 5 months ago #10829 by Cody Evans
Cody Evans created the topic: Engine cuts out after 20 min run.
I have a rotax 503 on a PPC. Runs great but the engine cuts out after 15-30min of flight. (Especially when heavily loaded). It loses rpm and drops to a low idle. If i let off power and try again, it grabs 5sec of power, then cuts out again. After the emergency landing, and shut down, it fires right back up and runs fine. I can't replicate the problem on the ground for some reason and I don't like emergency landings.
Engine sat for a couple years but has great compression and runs great (70hrs TT). I have rebuilt the MIC fuel pump. New fuel lines. The gas tank is 2ft below the engine but designed that way. Tank is vented and the vent is working. I have cleaned the carb. New plugs, I tried to check the motor for pressure in the bottom end and had trouble being sure I was sealing it all the way. I blew smoke in the vacuum line to look for leaks in the block and did not see any smoke coming from anywhere. After uncapping the intake and exauhst, the smoke poured out so I think the engine has a good seal. There is a fuel filter in line that I have not changed yet (next step) but it is positioned to work against gravity and I have not noticed any junk. I have drained the fuel tank and found no debris. Carb is not running rich or lean. Seams to be just right. It almost seams like I am running the bowl out of fuel at high rpms because it can't keep up.
Any help is apreciated.
Last Edit: 2 years 5 months ago by Cody Evans. Reason: Spelling

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  • Dennis Richardson
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2 years 5 months ago #10845 by Dennis Richardson
Dennis Richardson replied the topic: Engine cuts out after 20 min run.
HI Cody. 2 cycle engines do not like to be unused. Unless great care is taken most suffer from improper storage. The symptoms you describe would have me removing the exhaust manifold for inspection of the pistons and cylinders. Let us know if this reveals any issues.

Dennis
The following user(s) said Thank You: Nick Axworthy

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2 years 5 months ago #10848 by Nick Axworthy
Nick Axworthy replied the topic: Engine cuts out after 20 min run.
So after it goes to idle and and you let it idle...does it go to full rpm again but only for a short time and then back to idle again.

During any of this does the motor stop altogether.

Nick.

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