Have been seeing a lot of post about gas engine leaning out while in flight but run good on the ground, I converted this G23 a couple years ago and on the first flight it did the same thing, Got a coke can cut out a peace and installed it on the carb and problem fixed. took about 10 min.

Milton

OK.. Why does that work?
I can only assume you are protecting a port on the carb from direct airflow.

That indeed is how it works. It will not protect the port from pressure difference by cowl design.

Milton is one of the few that have paid attention and truly got the message. Preventing ram air from impacting the diaphragm opening is what it's all about. How it's done doesn't matter.

Before the week is over there will likely be more posts about engines "burbaling" when inverted or in knife edge in spite of all that has been written. There will be at least one more blaming the engine manufacturer for the condition.....

I take the metal cover off the carb and solder a short piece of tubing and attach a length of fuel line and put it thro the fire wall, then it is inside away from air flow. I have done this for many years , with no carb problems.

http://www.3w-modellmotoren.com/moto...28i/3W_28.html

Pe, why are not all engines arranged with the pressure reference at the manifold inlet such as the above 3W? It would seem that this would give accurate reference at all times, no?

No.
Even the 3W solution is not a cure-all.
The MVVS 58 has a carb cover with added nipple. Too many customers have no idea what this is for, and get confused. There seems to be no way to do things right for all.
If I were to build an engine, it would be bare to the bone, but equipped with a nipple to save the customer the hassle of soldering one on. Then I would HINT at what that nipple is meant for.

LMAO Scott Ellingson did the same on his Brillelli engines and guys were hooking the fuel line to them and then complaining the engine wouldn't run! I do that mod to all of my engines then run a tube to the inside of the fuse and into a pill bottle. Works great.

I run the atmospheric line into the fuselage and it works fine. Why do you use a pill bottle? Do you drill holes in the lid of the pill bottle for atmospheric pressure equalization?

I drill the hole slightly larger then the tube so it's not air tight. Just keeps the end of the tube away from any possible turbulence in the fuse.

I use the balsa box method suggested here on the forum several times. Just one pinhole in the box .... the porous nature of the wood seems to work very well for some reason.

the balsa box works, because it is nearly airtight, and SLOWLY equalizes to the outside pressure.Thus it gives a near constant atmospheric reference pressure on the carb membrane whilst preventing pressure fluctuations caused by model flight attitude.

What thickness balsa do you use and what is the box size dimension wise?

Karol

Doesn't really matter. I used what ever scarp I had laying around. It was about 1 inch square.

Like RTK, my boxes are just made from whatever scrap I have laying around. Usually 3/16" balsa glued with thin CA. CA in a brass tube into one corner and velcro the thing into a convenient place in the airplane. I think the last one I made was a little over 1" square and maybe 2 1/2" or so long.

Thanks guys, I figured as much but just wanted to be sure.

Karol

[img][/img]is this where I solder on the nipple?

Look at the last photo on this post. http://www.rcuniverse.com/forum/fb.asp?m=6289820

Also this one. http://www.rcuniverse.com/forum/fb.asp?m=6730611

It goes on that little hole in the plate. Actually, I don't solder them. I tap the hole out for an 8-32 and screw a muffler pressure nipple into the plate. Then I turn it over and grind the excess off of the inside of the plate so it can't harm the diaphram. Gives it a very tidy look.

If you want something neat, remove the plate, drill and tap a center hole for a muffler pressure tap (or solder on a piece of 5/32" brass tubing). Solder the current hole closed. BME sells a plate already set up for most Walbro carbs. I think it costs about $25.

http://www.bmeengine.com/html/accessories.htm


BME CARBURETOR DIAPHRAGM COVER


The new BME Carburetor Diaphragm Cover helps your engine to maintain consistent air pressure through your carburetor diaphragm at all times. This virtually eliminates the problems encountered when you adjust your carburetor on the ground, but experience inconsistent airflow and pressure entering your carburetor in flight, due to varying airspeeds.

This inconsistent airflow can cause your engine to go lean or go rich depending on whether your plane is sitting still, flying slow, or at high speeds. Machined from Billet Aluminum, this carburetor diaphragm cover comes with a nipple and blue mounting bolts.



It fits any engine using a Walbro SDC style carburetor, including BME twins, DA100 & 150, Quadra75 & 100, Brison 4.2 & 6.4 etc. The carb cover for for the BME twins also fits other engines using Walbro WGA ,WB and WJ series carburetors. The BME Diaphragm cover is now also available for the BME 44 & 50cc single cylinder engines.

This is a great item to help reduce carb mixture from fluctuating in flight due to pressure differences affecting the diaphram. Simply remove the old cover and install the new BME cover with the 4 bolts included. Then run a fuel line from the nipple to inside the fuse where stable air is.

PRICE: $25.00 each

That would work great except BME is defunct for all intents and purposes. Owner says he's had enough. That's why he doen't answer your e-mails or calls. Afraid you'll have to do without that neat little cover. Shame really, they're nice.

Al Lewis - you really think BME is history??? I've got a couple of his motors and if I can't get service, converting to a different power plant will be a huge nightmare

Harvey-- There is a person that is trying to acquire parts etc. Keith is gone, but ya never know what might happen in the future. I would run them until they drop.

Seems someone could have a nice little biz going just servicing all those motors that are out there