FlyingMonkey Posted October 26, 2014 Report Share Posted October 26, 2014 I cleaned out my drip trays (they had a light film of gummy residue) the other day, then flew almost every day this week. I then re-checked the trays, and there was a light fuel film there: The question is, what is normal for these trays? Link to comment Share on other sites More sharing options...
Tom Baker Posted October 26, 2014 Report Share Posted October 26, 2014 Andy, my opinion is they should stay cleaner than that. I see signs of the leak on the carb itself, but it could be coming from the rubber flange. Link to comment Share on other sites More sharing options...
CT4ME Posted October 26, 2014 Report Share Posted October 26, 2014 That's what was happening on my old bird, until carb cleanup and new gaskets. I'd say "normal" is clean, but not unusual to see some grime. That's why there is a tray there. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 26, 2014 Report Share Posted October 26, 2014 Normal is clean and no brown (91 oct) or greenish blue (100LL) residue. If you have more stains after a week then change the carb bowl gasket. When you do this make sure you bowl seats up into the groove designed for it in the carb body. If you get one edge not seated (easy enough to see) then it will leak. You can watch the video I posted on checking for carb bow debris and just change the gasket doing the same procedure. No more residue than you have it's a good bet it's the bowl gasket. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 26, 2014 Author Report Share Posted October 26, 2014 Sigh...Lockwood just replaced all the carb rubber and gaskets in June. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 26, 2014 Report Share Posted October 26, 2014 Andy, I see fuel stain on the carb higher than the bowl gasket. It shows above the Idle mixture screw, but looks dry higher up. Where the little BB is looks like the sealer is chipped away and discolored. Could be you need to reseal that. Link to comment Share on other sites More sharing options...
procharger Posted October 26, 2014 Report Share Posted October 26, 2014 If your carbs are out of sync vibration can cause them to puke a little. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 26, 2014 Report Share Posted October 26, 2014 Also make sure the clamp on the carb socket is tight. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 26, 2014 Author Report Share Posted October 26, 2014 BTW, it is the same on both sides: Is this considered dangerous or an airworthiness issue, or just a minor issue? Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 26, 2014 Author Report Share Posted October 26, 2014 Andy, I see fuel stain on the carb higher than the bowl gasket. It shows above the Idle mixture screw, but looks dry higher up. Where the little BB is looks like the sealer is chipped away and discolored. Could be you need to reseal that. What type of sealant is used there? Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 26, 2014 Author Report Share Posted October 26, 2014 If your carbs are out of sync vibration can cause them to puke a little. They were balanced in June at annual, and the engine has been running smoothly to my reckoning. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 27, 2014 Report Share Posted October 27, 2014 What type of sealant is used there? Roger says epoxy, but I'm not sure what variety. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 Since Lockwood touched the carbs last, I sent them a note with the pics I posted. Maybe they will have an idea what's happening. I will look everything over next time I'm out there and see if I can figure it out. I might have to run the engine with the cowl off to get fuel flowing through and see if I can see where it's seeping. It's time for an oil change, so I need run the engine to warm the oil before changing it anyway. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 27, 2014 Report Share Posted October 27, 2014 Andy, gaskets can leak at any time. There is no time limit for a good or bad gasket. Some can leak in 50 hrs. and some may last a 1000 hrs. Until proven otherwise just put in a set of bowl gaskets. That's the problem 90% of the time especially since it is so slow a leak. This is a quick easy fix and it will eliminate one possibility. The other two places to check, but not as common is the fuel fitting on the side of the carb that feeds them . I doubt this is a bad float because of where the fuel is and the leak is way too slow. The last place that is kind of rare is the MFG machining ports that have the small ball bearing in them. These are sealed with epoxy. They can ooze, but it is usually because someone got over zealous during cleaning or used a sonic cleaner and or too harsh a liquid cleaner on them. Just change the gaskets for now. I do one thing that most don't do here and don't have any repeat offenders. I rub the new gaskets with white lithium grease. Before anyone goes crazy about grease around a fuel or oil system here is why we use white lithium grease instead of others. This grease is also what we rub our "O" rings down with. White lithium grease is fully compatible with fuel and oil When it gets hot or comes into contact with fuel it dissolves back to an oil base and that tiny little bit gets absorbed back into the fuel or oil. It doesn't clump or gum up anything. Now I said rub the gaskets down on the top, bottom and especially the edges. Do no glob it on, just rub it in well. This just kind of pre-treats the gasket material. You do not need to get crazy here and wipe any excess off. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 Thanks Roger. The cork gaskets? Should I get a set of floats too and have my guy check them at the same time? Link to comment Share on other sites More sharing options...
Anticept Posted October 27, 2014 Report Share Posted October 27, 2014 What, they put in cork!? If you can, get the phenolic gaskets next time you replace them. Cork sucks. I had 200 hrs on a new set of carbs and the cork was already degrading rapidly on both. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 What, they put in cork!? If you can, get the phenolic gaskets next time you replace them. Cork sucks. I had 200 hrs on a new set of carbs and the cork was already degrading rapidly on both. Oh, I don't know, I just know some Rotax bowl gaskets are cork. Not sure what they are supposed to be for the 912ULS. I'm guessing these are the right ones, but it does't say what they are made of: http://www.cps-parts.com/catalog/rtxpages/15-00905.php?clickkey=41852 Link to comment Share on other sites More sharing options...
Anticept Posted October 27, 2014 Report Share Posted October 27, 2014 I have no idea. I got gaskets from leading edge air foils and they are phenolic (edit: maybe fiber per roger?). The only time I had seen cork was with the new engine, and they suck. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 I have no idea. I goet gaskets from leading edge air foils and they are phenolic. The only time I had seen cork was with the new engine, and they suck. I was just going to order some from CPS or Lockwood (I think CPS is cheaper by a buck). They are factory Rotax gaskets, so I guess they are whatever they are supposed to be...fiber, phenolic, viton, unobtainium...whatever. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 27, 2014 Report Share Posted October 27, 2014 Bing carb bowl gaskets from the Bing factory are cork. When you buy replacements from a Rotax distributor they will be a fiber gasket. I think they seal better too. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 Thanks Roger...ordered from CPS so they should be fiber. Link to comment Share on other sites More sharing options...
Runtoeat Posted October 27, 2014 Report Share Posted October 27, 2014 Andy, I had wet drip trays and had fuel stains running down my engine mount from where fuel leaking from my carbs flooded my trays enough to run thru a hole in the side of the tray where a nylon zip tie to connects that helps hold the tray in place. I had new float gaskets installed and this seemed to eliminate my fuel weep. As usual, Roger's advice is sound. One thing I notice though is the small ball which is epoxied in looks kind of funky in your picture. Hard to tell by you picture and it might also be the clamp on the rubber carb socket needs tightening, but if you still experience wet drip trays after installing new bowl gaskets, you might check out these two items. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 27, 2014 Author Report Share Posted October 27, 2014 Andy, I had wet drip trays and had fuel stains running down my engine mount from where fuel leaking from my carbs flooded my trays enough to run thru a hole in the side of the tray where a nylon zip tie to connects that helps hold the tray in place. I had new float gaskets installed and this seemed to eliminate my fuel weep. As usual, Roger's advice is sound. One thing I notice though is the small ball which is epoxied in looks kind of funky in your picture. Hard to tell by you picture and it might also be the clamp on the rubber carb socket needs tightening, but if you still experience wet drip trays after installing new bowl gaskets, you might check out these two items. Thanks Dick...my slight leak is obviously nowhere near as severe as yours was. I will get my mechanic to replace the gaskets, and we will check all of the connections and the epoxied ball when we are in there. The question that has not yet been answered: How much fuel in the trays becomes a safety of flight issue? Mine seems to just be a little film with no ppoling at all, but is any fuel in the tray a grounding condition? The weather is so perfect right now here, I hate to not fly while waiting for gaskets to arrive! Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 31, 2014 Author Report Share Posted October 31, 2014 Hmm...I checked yesterday and could not see any stains or other indication on the carbs of where the fuel in the tray had come from. I cleaned the trays out with Simple Green, and then went flying and checked again after landing, No fuel in the trays following that flight (6 touch and goes, about 0.8hr total). The day I did noticed the fuel in the trays, I had done some particularly aggressive maneuvering, including some ~2g turns and unloading to 0.2-0.5g for a couple of seconds at a time once or twice. Is it possible my carbs are fine in normal flight, but higher than normal positive g or less than 1g (but not negative) could cause a tiny amount of fuel to seep out? Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 31, 2014 Report Share Posted October 31, 2014 Do you usually remember to close your fuel valve but sometimes leave it open while in the hangar between flights? Link to comment Share on other sites More sharing options...
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