"End of the flight" Question

[Joe Messinger]

My P-40 profile does just fine until the end of the flight.  It then "stutters" through about ten laps before the engine finally quits.

It's powered by a FP .40 with muffler pressure.  The tank is a plastic 3 oz. Sullivan with a klunk.  The klunk appears to be working as it should and I have checked for air leaks in the system and found none.

As I mentioned, the thing runs smoothly until the fuel is about gone then it falters and revs back up repeatidly for 8-10 level laps before the engine stops.  Not a big problem but pretty annoying.

Anyone have an idea (ideas) as to what the problem might be?

Thanks ,

Joe

[Roger Vizioli]

       Just Some thoughts-
Flex tubing in tank too stiff, wont move to outboard side.
Clunk weight/pickup too far forward from rear of tank.
Flex tubing inside tank has a slit/break .......
R....

[Wynn Robins]

use a sintered brass clunk/filter....not an RC clunk....

like this one..... 



it removes bubbles, and gie you the cleanest cutouff you can possibly get with a clunk.....

[Joe Messinger]

Hi Wynn,

Thanks for the advice and photo.

I'll give that a try tomorrow as I'll be going to Brodak's to fly.

I've checked everything else and it appears to be okay.

Regards,

Joe

[Dennis Vander Kuur]

Joe,
Are you using the stock remote needle valve setup? I had an OS FP .40 do exactly what yours is doing - cutting in and out for 6 to 10 laps before finally quitting. The fix was to remove the remote needle valve assembly and then install a spray bar and needle valve at the venturi. Now I get a single burp and one lap later the engine quits clean. Hope this helps.
DennisV

[Greg L Bahrman]

use a sintered brass clunk/filter....not an RC clunk....

like this one.....



it removes bubbles, and gie you the cleanest cutouff you can possibly get with a clunk.....

Where do you get these??

[Wynn Robins]

www.sshobbies.com  or

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXD741&P=7

[SQ8s]

If you make it through the pattern and then runs bad ...I bet it's the height of the tank and or the clunk not long enough.

But after the flight..........??

[Sam Laughery]

Hey Joe,

I'll be at the field tomorrow about 2 or so.  I've had some similar probs with clunk tanks.  Maybe I can help.

See you tomorrow.

Sam

[Steve Helmick]

My RNV equipped OS .25LAS does the same thing, with a metal tank, no uniflow. Next time out, it won't have a RNV, and I don't think it will act the same. I also will be changing the tank to uniflow, tho. That will require height adjustments, but the run starts out quite rich and ends up a bit lean, so it's got to happen.    Steve

[Tom Perry]

Joe,

One other thing to try is shimming the tank so thr rear is about an eighth of an inch farther to the outside.