STEVESRCWORLD

My Feedback: (23)

I have a fpe 95cc engine in a 35% aeroworks edge. it runs great with plenty of power but when i roll inverted it stutters and doesn't want to run. it has never cut off yet but you can advance the throttle up to half and it runs the same, as soon as you roll it back over it takes right off. i have bought a new carb and installed and i am still having the same problem. any ideas? i need it to run the same in all attitudes. inverted is the only problem.

Tired Old Man

My Feedback: (1)

First thing to check is the fuel tank, line , and clunk. Is the clunk coming out fo the fuel supply when inverted? Install a heavy clunk and do some flying, then look elsewhere if it's not resolved.

STEVESRCWORLD

My Feedback: (23)

it acts like it's really rich when inverted. i already have a heavy clunk.

Rcpilot

My Feedback: (78)

It's the carb diaphram. When your inverted, the air flowing over and around the cowl is different. Thats creating pressure on ther diaphram--on the jet side-- and causing it to go rich.

Do a search for "balsa box" and "brass tube carb plate" in this forum. That will tell you how to fix it.

Truckracer

My Feedback: (19)

I agree with Rcpilet on this one. I have experience with 3 different FPE 4.2 engines..... I believe these use the same carb as the 5.8 and are very similar in all respects otherwise. All of these 4.2s had pretty much the same problem. Would cut out in different attitudes, at higher airspeeds, etc. They didn't like any direct airflow from the prop or slipstream around the carb area. One of these engines was cured by simply putting a baffle in front of the carb, the other by using a balsa box, the other was cured by selling it!

FPE recommends using an angle cut velocity stack also .... angled with the short part of the stack in the front. This helped one of the 4.2s and was provided free by FPE ... they might be standard equipment now, I don't know. I always thought these carbs might be helped some by changing the pop off pressure too but I was not aware of how to do that when fiddling with these engines a few years back. Overall, pretty good engines though when you get the bugs worked out. Pretty much a Brisson or similar clone.

Roger S.

STEVESRCWORLD

My Feedback: (23)

do you think soldering a brass tube on it and running a line inside the fuselage would help?

Truckracer

My Feedback: (19)

Yes, that might help and it is easy to try. On one of the 4.2s though, a tube to the fuse had no effect at all. I guess the pressure in the fuse was similar or the same as in the cowl. Your combination may be different. The balsa box seems to be more effective than just a tube but I was not aware of that method several years ago.

Do a search as suggested by Rcpilet .... there has been lots of things published about this subject.

Tired Old Man

My Feedback: (1)

Prolly just soldering on the bent brass tube would do the job. You could do a cheap non permanent test by drilling a 1/8" hole in the side of one of those red epoxy bottle inner seal caps and siliconing it over the diaphragm opening. It really does work.

Truckracer

My Feedback: (19)

I prefer the black seal myself! Good suggestion SS ..... 1/16" hole would be plenty big enough I would think.

Rcpilot

My Feedback: (78)

It's easy to solder in a brass tube:

Scuff the metal carb plate with a dremel sanding drum.
Scuff it right over the hole. About 1/4" around the hole.
Scuff a piece of 1/8" brass tubing.
Get out the silver solder and the flux.
Flux the brass tube and the metal plate.
Stick the brass tube in the hole.
Put the heat right in the middle of the metal cover plate.
Put your solder on the brass tube.
It will flow right into the hole when it's hot enough.
Let it cool and grind off any brass tubing on the inside to keep it from rubbing/puncturing the rubber diaphram.

Drill a 1/4" hole in the fuse former. Run a piece of cheap silicone glow fuel tubing from the brass tube into the fuse. Secure it. Leave it open on the end.

Go fly it.

STEVESRCWORLD

My Feedback: (23)

alright i soldered the brass tube on today and i am going to go ahead and build a balsa box also. i'll let you guy's know what happens.hole or no hole on the balsa box?

Tired Old Man

My Feedback: (1)

One thing at a time. Changing a bunch of things at once and you don't know what the fix was. If you need a balsa box, which I rather doubt, it would be a very small hole. You probably don't even need to run a tube, just deflect air from the opening.

Truckracer

My Feedback: (19)

Once again, have to agree with SS! Remember in one of my earlier posts about the 4.2, the problem was taken care of on one engine by just putting a plywood baffle in front of the carb. Had I known about it at the time, I'm betting that SS's plastic cap fix would have also worked. There are several methods to take care of this problem and they can all work for certain applications. Simple is probably best. As for the box, if you need it a pin hole is probably enough. Heck, the balsa by itself is probably pourous enough without any hole.

STEVESRCWORLD

My Feedback: (23)

well i have the tube on and will run some tubing into the fuselage. i'll let you know if it works on sunday evening if the weather holds. what if it doesn't work then should i try the box or what next?

Truckracer

My Feedback: (19)

If the tube to the fuselage doesn't help, try the box. Remember to reset your needles after every change you make. Just soldering the brass tube on the cover plate will change your needle settings a bit. Good luck

STEVESRCWORLD

My Feedback: (23)

which way? lean or rich?

Truckracer

My Feedback: (19)

Could go either way, adjust as necessary.

ljones5000

My Feedback: (2)

Here's a pic of how I did it on my 4.2

The tube runs into the fuse.

Larry

STEVESRCWORLD

My Feedback: (23)

well i flew today and still have the same problem after installing the brass tube and static line.half throttle and above it runs farily decent inverted anything under that stutters and pops. now what do i do? try the balsa box? an engine that wont run inverted isn't worth a crap on a 3d plane.

Tired Old Man

My Feedback: (1)

Remove the tube as it currently is. Re-install another short one that is at a 90 to the diaphragm and pointed to the right side of the plane as viewed from the front. Doesn't need to be very long, just 90 degrees to the right, aimed at the side of the fuselage/cowl. Retune the low needle for peak rpm at about 3k rpm, give or take a little, and then a crisp transition to max rpm. Then go fly.

STEVESRCWORLD

My Feedback: (23)

i don't quite understand what you mean by tune at peak rpm at 3k. do i set the throttle at 3k and adjust the lowend with it running till it gains maxium rpm at that throttle setting? please explain