edwal07

I have a new DLE 55RA and having a real problem with gas vapor lock. I installed the engine on the plane minus cowl for breakin. It did not want to start or pull fuel at first. I backed off the H and L needles about 1 turn and then it started pulling fuel (initial needle settings were 1.5 and 2). Really rich so I started a tune. Good high throttle 6850 on a 22x8. Backed off 1/4 turn to be on the rich side. Good idle but bad transition, adjusted low for better idle and better transition. Ran one tank (24oz) thru engine. Stopped before tank was empty and refueled. Tried to start engine, fuel is going to carb but no start, once you stop flipping fuel is flowing backwards toward tank and will not pull fuel into carb. This is vapor lock caused by high carburator temp. Removed the cover from carb and there is absolutely no fuel in the carb. Screen is clean and you can push fuel from tank to carb via vent line. Reinstalled cover after checking flap valves for any debris, none. By this time the engine and carb had cooled and fuel was now being pulled into carb. Engine started easily, however about half way thru a tank the engine stopped and again started to push fuel back into tank. Any suggestions or am I overlooking something. I have 8 gassers, DA, DL, and DLE up to 170cc and never encountered this problem. Help would be appreciated.
Ed

closetguy

My Feedback: (13)

is your muffler under the carb?

Ed Vollmer

My Feedback: (14)

I had the same problem on a ZDZ 40RE. It would fly just fine for couple of minutes and slowly lose power and eventually die if not landed. At first I installed an air exit louver at the top of the cowl above the carb to vent the hot air. That did not completely solve the problem.

I finally solved the problem with a fabricated .030 K&S aluminum shield between the carb and muffler. No problems after installing the shield.

The shield was 'L' shaped and attached to the motor mount box. It was cut such that it followed the curvature of the engine block and used slit silicone tubing to prevent metal to metal contact from vibration. The width was just a bit more than the width of the muffler.

Hope this helps.

edwal07

Yes it is the Rear Exhaust DLE 55. I have even put a piece of ply covered in metal tape used for ductingunder it to shield it to no avail. This is really getting frustrating. The cowl had additional cutouts on the front to allow more cooling air to go over the case and carb. So far nothing but letting it cool down stops the problem. My head temp running is 228 degrees with an air temp of 82 degrees at WOT. And it dosen't seem to make a difference, cowl off or cowl on so I know I have plenty of air flow over the head and engine.

edwal07

Thanks, that is what I have done with the ply mentioned above, I cut it to match the outline of the head and case body but did not extend it to the firewall. Maybe I need to try that. The one I made is tied to the standoffs with zip ties to hold it in place. I will put a piece of the metal tape against the firewall and extend it to the ply. That way any vibration wont interfere as it is somewhat flexable. thanks again, I will give that a try.

jerdavis

My Feedback: (3)

I've had trouble with carbs getting too hot from breathing in cooling air off of the cylinder (hot air). Getting a source of cool air to the carb fixed the problem.

Jerry

3136

Ed, it sounds like you are running it on the ground.
If that's the case, fly it and get some air flow over it.

pe reivers

Carb needs cool air, and also needs a heat dam between carb and engine, as well as between carb and mufflers. This is a general requirement.
Running the engine static will cause a lot of heat to build up in the crankcase, which subsequently is transferred to the carb. Static running is OK if kept to the bare minimum to get a carb tuned for reliable engine running and take rpm readings. All else should be judged while in flight, and corrected after landing, to be judged again in flight.

edwal07

Thanks everyone, it's tuned for flight. Will get it in the air this weekend and see how she does. Appreciate the advice, just never had one do this. Will update after flying this weekend.
Ed

bgw45

My Feedback: (1)

I have used exhaust wrap for some of the heat issues with my stuff. Mostly for protecting Hi-tension leads when I can't seem to find a proper way to route them. The wrap is not cheap, but it works.