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Polini engine 250 DS engine shutdown
Hi everyone how’s it going? In August, I purchased a used Rev with a Polini 250DS. The engine was sent back to Polini for a major overhaul at 101 hours and now has approximately 175 hours. I completed a Condition inspection including carb cleaning, fuel filter change, drained the tank to install Curtis drain valve, refilled with new gas (93 octane, 40:1 mix). I have flown it for a total of four hours, and have had five engine outs while in the air. The engine is just shutting down with no warning. Temps are perfect , and engine runs perfect… until it doesn’t! I’ve replace the fuel pump, because of a small leak, (that’s fixed) replaced the carb slide due to some missing Crome, no flakes were found The jets were clean , no blockage of the jets was found (that’s fixed) removed exhaust, and inspected the piston and side walls… no scoring. Compression check is good. Here’s the fun part… After multiple try’s I was able to get the engine to restart every time while picking out my emergency field.The trike was flown after every maintenance action ,so I’ve been having engine failures all month. Cannot duplicate the engine shutdown on the ground run ups . To prevent EGT limits from being exceeded, I cannot run the engine for an extended time on the ground, hence the test flights. Next idea might be with something grounding out the duel ignition ( maybe the start select switch) stator and battery drop checks are good during run up . Does anyone have any other ideas as to what might be happening with this engine? Or has anyone had a similar situation occur?
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7 Replies
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Hi Stephanie, I cant offer any mechanical advise, but I would say Do not fly anymore until you can find someone to help you pinpoint the problem and correct it. I cant imagine how frustrated you must be, but its not worth your safety. God Bless and best of luck!
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I had a similar problem years ago with a Rotax 447 – the engine didn’t quit but at times it would stumble. The problem was caused by a broken wire that entered the potted ignition box. While the copper in the wire was completely severed, the wire’s insulation was intact, allowing the intermittent contact. Look over your wiring paying particular attention to anywhere the wiring goes from a unsupported position to a fixed/bound position.
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Thank you for the info, I am new to the Polini engine. Flew a 447 on a different trike before this with no problems. The engine seems to be running fine until it just shuts down with no warning but will restart in flight. I was thinking the same thing. It might be losing all start input (like if you flipped the main start switch off). Does both drop checks fine. Onto wire troubleshooting. Thanks for the reply.
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You have checked the most important things. I would say ignition, but the 2 ignition systems are so separated that I don’t believe they can both fail together unless it’s at the kill switch which kills both at the same time.
The only thing I can think of that you haven’t checked is the float and needle system. I’m wondering if the bowl is getting sucked dry if the floats or needle and seat are sticking. I would replace both and go from there.
If compression is good, spark is redundant, then I’m leaning towards fuel supply. And since the fuel system is so very short and simple and you have replaced the filter (hopefully not a paper filter), then the possible fuel supply problem may reside inside the carb.
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I was able to duplicate the problem on deck on Monday due to cooler weather (not EGT limited). Checked wiring with meter, no discrepancies. Checked float level and adjusted floats more consistent with a Bing carb. Found that anything below overflowing the carb bowl will cause starvation so I ran the bowl overflow drain over the carb so it works like a sightglass to see fuel level in the bowl instead of draining overboard. This was the setup when I purchased the trike and I now understand why it was rigged this way. On my condition inspection after purchase, I adjusted the carb floats to the recommended 19 mm printed on the Polini manual for the carb. Seems to be incorrect for my installation and caused fuel starvation at high RPMs. After adjustments, flew trike for 40 minutes with no problems. Thanks for everyone’s input.
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Wow! So glad your motor is running without issue now. It’s really awesome to see this forum at work answering questions. That’s what’s it’s all about!
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Years ago i had a Rotax 503 in a Quiksilver sport. I rebuilt the carb and noticed the carb floats were not set to specs. I set the floats to specs and had an engine out while flying. I was able to make the landing back at the airport. I rechecked that I had set the floats to spec and sure enough they were. I put the floats back to where they were before i rebuilt it and sure enough it never failed again. I had a hard time believing that the manual was incorrect but that was my experience. I triple checked the manual and am sure to this day it was not correct in the manual. I have noticed that when I check older versions of Rotax manuals certain specs have changed at times.
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