Author Topic: FOX 35 QUESTION {imagine that} (Read 2698 times)

Bob Disharoon · « **on:** April 01, 2007, 03:43:02 PM »

fox 35
2 hole spray bar, holes facing correctly
profile mount
brodak 3 inch tank on a buster, pickup mounted @3/8 above spraybar centerline, no pressure, nothing plugged
new fox long glowplug
engine stars easily on prime, stops
needle richened.. 6 to 7 turns
engine runs longer, gradually dies after 15 to 30 sec.
onlooker said tank was a blur when running..mucho vibration
need to solve this....maybe mount tank on a foam layer?
Frustrated old retread, tryin to get goin for Brodak!

Leester · « **Reply #1 on:** April 01, 2007, 03:52:08 PM »

Bob: Thats what I use, I use the foam out of ST engine box packing. The black stuff, My K&B 35 Stallion acted the same way when I put the foam under the tank against the fusalage (profile) it ran fine. I know it's to late now but I also put in longer motor mounts.

Paul Taylor · « **Reply #2 on:** April 01, 2007, 04:01:09 PM »

Bob,
Can you run it on the beach? Off the plane?

Do you have a filter installed?

I am no expert, but maybe start with the tank setup at center line of the NVA. 3/8 in seems a little high.

Good luck! Hope to see you at Brodaks.

Paul

Bob Disharoon · « **Reply #3 on:** April 01, 2007, 05:12:02 PM »

Leester..wll do in the a.m.
got the foam from old engine boxes keep ya posted..thanx in advance, cause I know youve got the CURE!..BOB

Bob Disharoon · « **Reply #4 on:** April 01, 2007, 05:17:44 PM »

Rootbeard..I spent a coupla hours ready every old thread on the board and , if I remember correctly, the main reply was to elevate said tank above nva for some sort of inverted flying quantum physics sort of thing that I couldnt wrap my brain around..these guys around here are NOT dumb, 4 sure!!

Alan Hahn · « **Reply #5 on:** April 01, 2007, 05:20:27 PM »

It sounds like you aren't able to get into 4-stroke mode --it is dying lean. Make sure your needle is sealed. A piece of fuel tubing over the threads may help a lot. Any air leaking by the threads will just kill fuel draw.
Also I assume it is already broken in.

Ralph Wenzel (d) · « **Reply #6 on:** April 01, 2007, 06:01:04 PM »

One item not yet mentioned is the possibility that the spray bar is partially clogged. That could cause the symptoms you describe: "Runs a few seconds when NV is opened correctly; runs longer when NV is opened a lot more". And I'd be strongly tempted to replace the Fox plug with a K&B 1L or some other similar hot plug; Fox QC doesn't always show up for work . . .

For tank insulation, I've had good luck using the thin (1/4") "bubble wrap".

Bob Disharoon · « **Reply #7 on:** April 01, 2007, 06:24:21 PM »

thanx...its dying rich, 4 sure..dial it in lean and slow death..also, spray bar is clean as a whistle..I think Im really close to solving this..keep writing..it keeps an old man alive....remember,now..if it aint right by Brodak...its your fault..by the way, wheres Billy G to join in on this?!?

Bob Disharoon · « **Reply #8 on:** April 01, 2007, 06:26:53 PM »

Alan..I will also follow your advice in the a.m... good advice, thanx

Bill Gruby · « **Reply #9 on:** April 01, 2007, 06:30:05 PM »

Bob;

I'm right here been watchin for a while now--------you don't need me you got a lot of help and they haven't given you any bum scoop yet. Keep after it you are on the right track.

"Billy G"

Bob Disharoon · « **Reply #10 on:** April 01, 2007, 06:38:50 PM »

I shouda known you were lurkin out there..are we gonna see you at carmicheals?..sure hope so, now we can recocnize you !!!!!!!

Bill Gruby · « **Reply #11 on:** April 01, 2007, 06:53:55 PM »

Bob;

You betca bippy I'll be there. Wouldn't miss it for the world. Now you get back to what you are doin with that Fox .35, show us what you're made of.

"Billy G"

Willis Swindell · « **Reply #12 on:** April 01, 2007, 07:34:39 PM »

Try turning the prop 180º.
Willis

Jim Kraft · « **Reply #13 on:** April 01, 2007, 07:42:45 PM »

I have found if you are running uniflow that 3/8" above center line is about right for a profile and Fox 35, but with a standard vent tank I mount the tank about on the center line. This also helps eliminate the Fox burp for some reason. On uniflow they burp, and standard vent they do not.

Marvin Denny · « **Reply #14 on:** April 01, 2007, 08:53:40 PM »

DARN Jim now you done let our sekrit out on the burp
Bigiron

Another thing If the engine is not THOROUGHLY broken in it sometimes vibrates. Installing a Stuffer backplate helps the vibration problem some too.
B

Bill Little · « **Reply #15 on:** April 01, 2007, 09:48:08 PM »

Marvin, Does it take about an hour to an hour and a half to break in a good Fox 35 on the bench?

Bill <><

Bob Disharoon · « **Reply #16 on:** April 02, 2007, 06:34:58 AM »

The engine is a vertical 2 bolt muffler job which, I think, is 60s 0r 70s vintage..bought it fron a guy who flew it plenty and loved it..cant talk further . gotta work this out before Billy g catches me

Marvin Denny · « **Reply #17 on:** April 02, 2007, 08:50:07 AM »

Quote from: Bill Little on April 01, 2007, 09:48:08 PM

Marvin, Does it take about an hour to an hour and a half to break in a good Fox 35 on the bench?

Bill <><

Bill it depends a lot on the vintave of the engine. A new 50th anniversary takes only a few tanks to get it broken in (less than 30 minutes) while a really good 40th anniversary usually takes a half gallon of fuel and I have seen some of the earlier versions that took a gallon or more.
As the engine reaches the end of the tank and leans out to die, if it slows from tightness any at all, it needs more breakin.

Fox 35s are funny creatures that way.

Bigiron

Bill Little · « **Reply #18 on:** April 02, 2007, 09:51:11 AM »

Quote from: Marvin Denny on April 02, 2007, 08:50:07 AM

Bill it depends a lot on the vintave of the engine. A new 50th anniversary takes only a few tanks to get it broken in (less than 30 minutes) while a really good 40th anniversary usually takes a half gallon of fuel and I have seen some of the earlier versions that took a gallon or more.
As the engine reaches the end of the tank and leans out to die, if it slows from tightness any at all, it needs more breakin.

Fox 35s are funny creatures that way.

Bigiron

Thanks, Bigiron. I have known the older Foxes to take quite a while to break in, didn't know that the new one doesn't!

Bill Gruby · « **Reply #19 on:** April 02, 2007, 10:00:10 AM »

Quote from: bob disharoon on April 02, 2007, 06:34:58 AM

The engine is a vertical 2 bolt muffler job which, I think, is 60s 0r 70s vintage..bought it fron a guy who flew it plenty and loved it..cant talk further . gotta work this out before Billy g catches me

Im still watchin ya, you're doin OK LOL "Billy G"

Bob Disharoon · « **Reply #20 on:** April 02, 2007, 12:50:21 PM »

Now how did I know that.........yur breathin too hard

Jimmy R. Jacobs · « **Reply #21 on:** April 03, 2007, 12:01:08 AM »

You may have a bad tank, some time's the copper tubing inside the spilt. I would check the tank.

Jim

Ward Van Duzer · « **Reply #22 on:** April 04, 2007, 02:21:43 PM »

Old mouse pads make good vibration dampers. But I like to load the back of the tank up with GE Seal and squish it down on waxed paper until the silicone is about a 1/4 in thick at the rear of the tank, and an 1/8 of an inch on the front. Let it cure overnight and cut off the excess from around the edges.

Also helps to use a good metal filter. Bubbles don't go through the screen!

Bob Disharoon · « **Reply #23 on:** April 05, 2007, 07:18:50 AM »

I stole one the wifes scrubbing pads..the green one thats 2/3 sponge and 1/3 foamlike scub stuff{for those stubborn stains}, cut it to shape and stuck it firmly on back..we will see

Bill Gruby · « **Reply #24 on:** April 05, 2007, 07:56:29 AM »

Hi Bob;

I know you have thought of this already buuuuut you better check the foam part of that pad to see if it is user friendly aka FUEL PROOF. Don't ask how I know.

"Billy G"

More coffee please

Willis Swindell · « **Reply #25 on:** April 05, 2007, 08:40:31 AM »

I remember now, The bottom muffler screw hole is taped through the case and you are losing crank case pressure. I had a friend have that problem 15 or 20 years ago and took fore ever to find it.
Willis ;DInsert Quote
The engine is a vertical 2 bolt muffler job

Bob Disharoon · « **Reply #26 on:** April 05, 2007, 10:04:53 AM »

So the solution would be plug the hole with a machine screw? I ran it with a muffler and it was doing the same thing, though.

Bob Disharoon · « **Reply #27 on:** April 05, 2007, 10:08:23 AM »

Good point Billy..in my hurry to go with the first fix I could think of, didnt consider the fuel issue..guess Im back to my hole to do some sperimentin.

Bob Disharoon · « **Reply #28 on:** April 05, 2007, 10:10:54 AM »

One more thing..I know the pad is wife proof..isnt that enuff?

Bob Zambelli · « **Reply #29 on:** April 05, 2007, 11:00:20 AM »

Hey, Bob - keep a eye on your mailbox.

Soon you will see a box containing 3 little animals - very nice ones at that!

Priority mail, of course.

Bob Z.

Bob Disharoon · « **Reply #30 on:** April 05, 2007, 01:42:11 PM »

Thanks!..like a kid before xmas

L0U CRANE · « **Reply #31 on:** April 07, 2007, 02:46:14 AM »

Bob,

...worst case: consider strapping the tank on with rubber bands. Anything 'harder' transmits much vibration...

Also, 3/8" seems a bit much to me. I seldom need more than 1/4" to lock the RPM/airspeed the same both ways.

Somewhere in here is my description of a "wig-wag method" to check tank height before a first flight. If you run through that, the engine should run decently upright and inverted, NOT cut out, and be within a whisker of the final 'height' locaton.

Luck!

Author Topic: FOX 35 QUESTION {imagine that} (Read 2698 times)

Alan Hahn

Willis Swindell

Willis Swindell