Jump to content

Fuel in drip tray


Runtoeat

Recommended Posts

After my 5 year rubber change, I note that I now have fuel which comes from the intersection of the air inlet hose and the carb inlet. It drips down from the hose clamp and drips into my drip tray. Both carbs are doing this. I had the carbs completely rebuilt by a major parts supplier. I had no drips before the rebuild. My friend's CTLS has developed the same probem but on just one carb. In order to leak here, the fuel has to come from a point insdie of the carb and then flow against the incoming air and travel upstream towards the inlet of the carbs. I was told by a Lockwood tech that this can happen if the needle valve is not completely shutting off. He said to remove the carbs, hold them upside down so the floats are shutting off the needle and apply 5 to 6 psi and see if the needle valve holds this pressure without leakage. I have not tried this because I'm still burnt out from doing the 5 year rubber change. It is not a large leak and basically just leaves my hose clamp and drip trays wet after a flight. Has anyone else had drips from this area. If so, were you able to eliminate it?

Link to comment
Share on other sites

Hi Dick,

What's causing the leak if it is in fact coming from this location is either a loose fuel fitting where it goes into the carb, not my first choice unless someone took this off.The common cause is someone did not know how to set the float level which in turn would do a poor job of controlling the fuel and if the float level is too high it will allow fuel to come out the throat or the vent tubes. Check your little clear plastic vent tubes for any fuel after a run. Since the carbs were just done this is my first choice for a problem. They may have bent the float arms. I really doubt it is a bad needle valve.

Link to comment
Share on other sites

Hi Roger. Thanks for the info. Your suggestion to check the float levels seems to be correct. I went onto the Rotax forum and see that you and other's have commented on the float level there - a lot of good info on our Rotax engine at this forum. I copied the directions for removing the carb by just removing the enrichner lever and leaving all the cables attached. Also copied the info for correct float height. Is removal of the enrichner arm and lifting out the slide a good way to get the carbs off the engine so my mechanic can check the levels?

Link to comment
Share on other sites

Hi Dick,

 

IF I'm going to remove the carbs I mark the throttle cable on each side of the attacment with a black marker. Then I remove both cables. Just removing the arms doesn't let you completely remove the carb. Then you have to remove the furl line that goes into the side of the carb. Any time you pull a carb make sure you do a carb balance. I just happen to know the guy that moderates that site. :rolleyes:

Link to comment
Share on other sites

Just something to put in that mental file cabinet.

 

Just a side note for those checking your float level. The floats when in the fuel should have the float pin equal to the fuel level. If the pin is below the fuel surface especially compared to the opposite float then it is bad and needs replacement. Some float do go bad and when that happens they can sink or flake. The flakes can get into the carb jetting.

Link to comment
Share on other sites

By the way, removing the drip trays on my Sky Arrow was a royal PITA - tiny bolts and nuts that were hard to maneuver into place and easy to drop.

 

Being Experimental, I turned the mounting holes into mounting slots with a Dremel tool and a cutoff disk:

 

6795714158_90d0e1fd5a_z.jpg

 

Now I just loosen the nuts a few turns and the drip tray drops right down and off with the hardware still in place.

 

Makes it a lot quicker and less frustrating.

Link to comment
Share on other sites

Ed B - you should be the official photographer for this site. Absolutely fabulous images.

 

Thanks, Fred.

 

Virtually all of the recent ones were taken with my iPhone4 and edited in iPhoto, then posted to Flikr.

 

Added the circle and arrow on the voltage regulator pic using an app called Skitch on my iPad.

 

These new "pocket computers" are really quite amazing.

Link to comment
Share on other sites

Hi Tad. I just sent my carbs in for complete overhaul and all passageways have been boiled out and new parts, including the float needle with new viton tip, have been installed. It isn't clear to me why I have symptoms of a leaking float needle with a new one installed. If it still seems to you that I should have you look at my carbs, I can give you a call to discuss this. Thanks.

Link to comment
Share on other sites

You should not have any issues with a cut Viton needle valve or the tens of thousands of Rotax 912's in the world would be having issues. I can see an individual one or even an old one, but you shouldn't have an issue with the newer style. The only way to alter this would be to trim the needle valve seat and if it gets damaged it could cost $1100 for a new carb. It needs a clean sharp edge to seal and rounding or tapering may invite trouble down the road.

Link to comment
Share on other sites

Another thing to check is the washers on the fuel line where it attaches to the carbs. One of mine was left off by mistake when the carbs were rebuilt and it leaked from there into the tray even when the nut was tight. WF

Link to comment
Share on other sites

WF, thanks for the suggestion to check the fuel inlet fitting. While the cowls were off, I checked all of the hose clamps that were involved with the 5 year rubber replacement and found all of them needed tightening, including the banjo fitting that ties into the fuel feed line to carbs. I'm leaning towards the float level not being set right but will check the fuel inlet fitting before going further.

Link to comment
Share on other sites

WF, did the installation of the second set of new float needles stop the fuel dripping into the tray? If so, it appears that perhaps there are quality issues that prevent some float needles from shutting off fuel flow. Your thoughts on this would be appreciated.

Link to comment
Share on other sites

  • 3 months later...

My partner and I have noticed a small amount of fuel in the drip tray after flight (as seen through the oil check door). We recently wrapped the exhaust headers, so I'm not sure if the dripping was happening in the past and evaporating before landing due to the hotter header temps under the tray. The float bowl gasket was just replaced and the drip continues.

 

The engine runs smoothly with no hint of flooding. There is no fuel coming from the air vent tube and no indication of dripping fuel where the inlet line is connected to the carb.

 

 

My question is what are the next steps to resolve the drip? I assume float valve replacement should be tried. Nothing has been done to the carb to change the float level adjustment, although the floats themselves were changed out due to the old ones flaking. Is there a way to check the float level adjustment with the carb left on the plane? Also, can the float valve be replaced without removing the carb?

 

Roger Kuhn

Link to comment
Share on other sites

Hi Roger,

 

This won't be due to a float issue. Someone still hasn't placed the bowl gasket in quite right. Re-do the bowl gasket. Many catch an edge on the gasket and it doesn't get seated fully in the carb edge groove. That is the only place it should be coming from unless your fuel line into the carb has a loose fitting. Which gasket are you using, cork or fiber?

Link to comment
Share on other sites

Hi Roger,

 

This won't be due to a float issue. Someone still hasn't placed the bowl gasket in quite right. Re-do the bowl gasket. Many catch an edge on the gasket and it doesn't get seated fully in the carb edge groove. That is the only place it should be coming from unless your fuel line into the carb has a loose fitting. Which gasket are you using, cork or fiber?

 

Roger,

 

Thanks for info. We used the fiber gasket, which was also the type replaced. There is no evidence of fuel residue around the fuel line fitting. I haven't tried to tighten the connection.

 

How did you eliminate that it's not a float or float valve issue? Also, would it be worth changing out the float valve to the new viton type as preventive maintenance? I did this on my Rans Rotax several years ago and it was done with the carb on the plane. I recall there was room to knock out the float lever pin with the carb still mounted.

 

Roger Kuhn

Link to comment
Share on other sites

Send me your carbs and i will make the drip go away. there is only one thing that causes this and I know how to fix it.

 

 

Tad,

 

Thanks for input. What is the "only one thing"? If we're going to remove and send the carbs out, I'd like to know what will be done. Also, would it be worthwhile to replace the other carb parts not already done in the rubber change out. I believe the float valves, o rings and main jets remain to be done.

 

Roger Kuhn

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...