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Fuel from carbs when parked

PostPosted: Fri Feb 05, 2016 4:47 pm
by rmullins
I have fuel leaking from my carbs when the plane is parked. Got to be floats, right? I installed a rebuild kit last fall that included a new float needle valve, and also replaced the floats when Rotax released the advisory. Still leaking, comes out both carbs. I found that my fuel shut off was defective and I replaced it last weekend so its no longer a problem as long as I remember to shut it off, but I don't remember this being an issue in the past. I put the carb on the beach and it shuts off fine and the fuel level is almost exactly a half inch from the top of the bowl, which from what info I can find is where it should be. I also have rough running at idle which I'm wondering is related. Any thoughts, suggestions?

Re: Fuel from carbs when parked

PostPosted: Fri Feb 05, 2016 8:06 pm
by AV8R Paul
I just had the same problem in my Kitfox. I had checked the Floats (both sides met the weight specified), checked the Serial Number and Date of manufacture of both the engine & the Carbs and according to everything I did not have a float sinking problem did not fit. In July the pilot side Carb started leaking really bad, flowing would be a better descriptor. I would have guessed it was something in the needle valve & seat. I pulled both Carbs and sent them to Lockwood to be rebuilt because of the 200 hour rebuild. I sent both Carbs off to Lakewood for rebuild. Then in January on a trip to Sebring it started getting very difficult to start and progressively got worse until I got to Meridian Mississippi. It was on the pilot side Carb again. I was broken down in Meridian Mississippi. I finally found a mechanic with a weight scale and a spare set of floats. When we pulled the Pilot Side Floats one of the two floats were sinking. With it being difficult to start I ended up damaging the Sprag Clutch trying to start it. I stopped at Southern Mississippi Light Sport to have Ronnie look at it, it was running much better after the float was replace, but it continued to be a BEAR to start. I got as far as Tallahassee Florida, and the next morning it would crank, grind, and then kick back every time I attempted to start it. I got to tow my plane back from Tallahassee, and I am now in the process of pulling the engine to replace the Sprag Clutch.

Don’t Hesitate to tear into the Carbs and get this fixed. Go read Rotax Float Service Buliten, if the floats are sinking, weigh them and replace them if they are bad.

Re: Fuel from carbs when parked

PostPosted: Sat Feb 06, 2016 10:21 am
by alan
The problem I had with fuel leaking from the carbs was the seat itself. The seat was slightly irregular so I used a drill bit (or was it a countersink?) and counter sunk it very slightly, then polished it with a wooden dowel. This greatly helped with the drip. I just used my fingers and a very light pressure and most of the work was with the dowel. Then the carb had to be very carefully cleaned. This was several years ago and no leaks since.

Also, the spray clutch is in the easily removed gearbox. Removing the engine seems unnecessary.

Alan

Re: Fuel from carbs when parked

PostPosted: Sat Feb 06, 2016 10:02 pm
by AV8R Paul
Last time I checked the Sprag clutch is on the back of the engine. With my installation the only way I can get it out is to remove the engine. The Sprag housing is in his hand, and the clutch gear is on the crankshaft. He's pointing to it with his index finger.

Re: Fuel from carbs when parked

PostPosted: Sun Feb 07, 2016 9:44 am
by alan
Sorry. All this time, years, I had assumed it was in the gearbox.

My bad. :shock:

Alan.

Re: Fuel from carbs when parked

PostPosted: Sun Feb 07, 2016 8:54 pm
by R Rinker
I've got thousands of hours on Lyc & Cont. engines. The problems with them are straightforward to to deal with. These kinds of issues are what we have with our Skidoo's, and exactly why I dread spending $25,000 on a Rotax...

Re: Fuel from carbs when parked

PostPosted: Mon Feb 08, 2016 10:14 am
by AV8R Paul
The Sprag clutch is seldom a problem on Rotax. I wonder what a Starter would cost on a Lycoming or Contenental? The Sprag Clutch is about $250, Plugs $3.00 each.

Alan no problem, I wish it were in the gear box.

Re: Fuel from carbs when parked

PostPosted: Mon Feb 08, 2016 6:21 pm
by rmullins
I don't have a scale that will weigh something as light as the floats, but I replaced my floats last fall when Rotax announced the AD on them and nothing changed. I'll have to check around for a scale but I'm skeptical. I'm pretty sure there was a new brass seat for the float valve in the rebuild kit. It's been a few months and my memory isn't what it used to be. Still I appreciate the suggestions.

Re: Fuel from carbs when parked

PostPosted: Mon Feb 08, 2016 7:44 pm
by R Rinker
Yes, I see your point Paul. You don't have to pay inflated prices for certified parts. I never had a starter fail in the field because we never ran one until it totally wore out. TBO worked for us. My struggle is whether I could survive running a rotax in the Arctic regions. Down where you are and with recreational flying styles, I guess it satisfies enough customers. But in the isolated, challenging conditions in the north it's a whole different ball game. Our survival depends on our ability to be honest with our equipment and not in denial. The initial purchase & new installation of the rotax isn't much, if any, cheaper than, say an O-200. We are out of the mainstream here, and don't have the opportunity to have a lot of exposure to the Rotax. A friend of mine here, locally, got his homebuilt in the air last spring, and lost the summer flying season dealing with a Rotax carb issue...took all summer to get it working right, and he even took the factory engine training course. I still have yet to know anyone running one that hasn't had issues that I find unacceptable or hard to accept. I'm told that a lot of people are happy with them, just unfortunate that I don't know any of em. One big issue is that if the airframe is basically designed for the Rotax, then it's not an option to put another 20 lbs. up front & bigger fuel load, because there 'will' be operators who will fill the seats with two big guys & need max performance. It might not be an option under those circumstances to use anything other than the Rotax.

Re: Fuel from carbs when parked

PostPosted: Tue Feb 09, 2016 1:11 am
by AV8R Paul
My rotax hates cold weather, if it gets below 50 degrees, I better start the heater, and the heat strips. However I like 4.5 to 5 gallons per hour.

I am a certified LSR-A and certified in Rotax Repair. It is a nice engine. However, if it breaks crap.

Re: Fuel from carbs when parked

PostPosted: Tue Feb 09, 2016 11:53 am
by moving2time
Rick, you always seem to use your Highlander a lot. What kind of time do you have on your Rotax. Just curious if it is an old age related issue like many older mechanical devices that are worked hard. Joe B

Re: Fuel from carbs when parked

PostPosted: Tue Feb 09, 2016 3:00 pm
by rmullins
It's only got 500 hours on it but it's 8 years old. I had a problem when new of the fuel tanks dissolving and depositing a layer of what looked like molasses in the intake manifold. I'm wondering now if maybe it could be the needle valve seats. When the temps get back above freezing again I'll pull the carbs off and take another look.

Re: Fuel from carbs when parked

PostPosted: Tue Feb 09, 2016 4:37 pm
by scubarider2
Rick, I had my carbs inspected and that "goo" from the tanks did not seem to gather there. For me anyway.
Dennis

Re: Fuel from carbs when parked

PostPosted: Wed Feb 10, 2016 11:46 am
by AV8R Paul
I’m guessing you are using Autofuel with alcohol, AKA ethanol.

In my Kitfox I had the same problem. I was flying one day, and I noticed that on approach for landing when I chopped the throttle, there was a minimal reduction of RPM. After shutting down the engine and doing a Dead Stick Landing, I went to the hanger and started trouble shooting. I notice the Fuel Sight Gages had YELLOWED, they were very brownish yellow in color. I had used about 3 tanks of ethanol, and I got the same brownish yellow “goo” or molasses in the carbs & cross over intake. Supposedly my tanks were Ethanol fuel compatible but they were NOT. I removed the Air Filter and touched inside of it it was very sticky. I removed the air-box, and found the Carburetor slide mechanism was actually sticking in the up position as you advanced and retarded the throttle. I was attending a Rotax Service & Maintenance Training Class, and I removed the Carbs to inspect them in the Class. YES, the Goo will coat the entire inside of the carburetor, Dean Vogel from Lockwood and the entire class got to look inside with the Float Bowl off and saw that it was coating the entire inside of the Carb, it was also on the Carburetor slide mechanism and, and covering the needle valve in the Carb. I had both Carbs rebuilt @ Lockwood, replaced all fuel lines, and quit running Auto Fuel, and went to exclusive 100LL.

Per John at Kitfox it was the alcohol stripping the Mold Release from the inside of the tanks. I sloshed the tanks with 1/2 Gallon of 100LL & 1/2 Gallon of Acetone mix. He recommended doing this 5 times. I haven’t had the problem since. Caution: when I sloshed the tanks the Acetone caused the Sight Gages on the Kitfox, which are made of Tigon tubing, started developing cracks which I noticed during my next flight. I DO NOT believe whomever is manufacturing the tanks for Kitfox were using epoxy that was safe to use ethanol fuel. I would bet the same is true of your tank manufacturer. I personally believe the ethanol is stripping the epoxy out of the inside of the fiberglass fuel tanks.

Re: Fuel from carbs when parked

PostPosted: Thu Feb 11, 2016 4:19 pm
by rmullins
Ohio has a law that mandates alcohol in auto fuel, and before I found out I could get alcohol free at the boat marinas I used it for the first 150 hrs because I thought that was the lessor of two evils. I would rather deal with alcohol damage to the fuel system than the damage that lead does to the engine valves and gearbox. I have been running only alcohol free and occasional 100LL for the last several years. I put rebuild kits in my carbs last fall and had them completely disassembled. I didn't find any of that goo in them then.