Rotax 912 Burps/Skips in flight

[newamiga]

Guys .. I had a strange experience a couple years ago while flying a Gobosh out to Oshkosh. Right as we flew over the Mississippi river the engine sort of "burped" or "skipped".. hard to explain exactly but it was only a momentary issue. We ended up making a landing short of OSH and found a fuel leak at one of the carbs. It turned out to be a crimped bowl gasket that was replaced and the plane seemed to fly fine. Fast forward a couple years and I know this seems unbelievable but as I am about to cross the Mississippi in my own Gobsosh this year the engine did exactly the same thing. I suspected possible carb icing and put on the carb heat and it didn't re-occur. The next day we had another instance and again carb heat seemed to clear it. I then had some roughness in the engine running on the way back to Colorado. I am bringing it into the shop next week to get the spark plugs replaced, carbs balanced, bowls dropped to see if there is anything in them.

Has anyone had a similar experience or ideas on what else it could be?

Thanks Carl

[ct4me]

I'm betting on a tiny something in the bowl... your symptoms seem to parallel similar instances reported here and on the CTFlier forum.

[roger lee]

Hi Carl,

Seems your Gobosh is afraid of water.

I would suspect the carbs. Something small enough could get sucked up and momentarily interrupt the fuel flow then get passed right through the system. You may also have something floating in the carb bowl that can move around with the fuel. When someone tells me that had a power reduction or a hiccup that is at least the first place I look, in the carb bowl to rule it in or out. It only takes a couple of minutes on each side. I have posted a video of how to do this and basically do a self rescue instead of being stranded on www.ctflier.com forum under maint. pictures and videos. I has saved a number of people especially after a hose change.
I really doubt it was electrical.

[newamiga]

Thanks Roger.. yeah it seems really strange as it was two different Gobosh's that it happened in. I think the first one we were a little further north up the river. Is it possible for debris to get past both the gascolator filter as well as the fuel filter into the carb?

Carl

[roger lee]

Hi Carl,

yes and no. The gascolator screen is usually 100 micron mesh so most stuff stays there. The fuel pump has it's own screen too, but pieces of hose can flake off or flakes can come off the carb floats and cause your clog.

[drdehave]

As indicated in another thread, here, someplace, I've had about six similar experiences in running my Sting Sport 850 hours. Each one has always been something--from a tiny spec of grit to a much larger piece of rubber--in one of the carb bowls.--Rich