Was just reading my September 09 issue of M.A.N magazine and came across an article in the Clarence Lee's Engine Clinic discussing the effects of ethanol and gasoline in the Walbro carb, which recommends that in an effort to avoid debris clogging the small cup shaped metal screen in the carb, that it be removed and an external filter fiitted.

This is certaintly contrary to my thinking and way of doing things and just wondered how correct this information is, especially for those new to gassers or for those who tend to follow or take the written word in mags as gospel.

Karol

I wouldn't remove the screen but would use a external filter

I've had to take too many carbs apart at the field to clean the fuzz out of the screen

Fitting the external filter, a felt one in a clunk, is a good idea. Removing the little screen, is a senior moment.[sm=thumbs_down.gif]

I thought the problems associated with ethanol in the gas and the carbs had more to do with the older materials/membranes used. Since newer carbs and/or carb kits come with newer materials designed to further withstand some of the additional additives, worst case scenario, get a carb kit for your older carbs. Perhaps I've misunderstood this concept along the way though....I can't imagine removing the internal carb screen to avoid a problem. Why not promote routine maintenance to inspect and clean....?

The new Zama and the Saito carbs have Mylar diaphragms. I don't know about the new Walbros.

Removing Filters / Screens = Increasing Failure Rate and Maintenance
Personal choice.

I wondered about that advice as well when reading it.
It is not a good idea, considering all the debris I find in there even when using the best of fuel filter combo's in tank and fill system. Much of the debris I find would have caused carb adjustment need by itself, not to say it could have caused major carb problems. Some is gum, some is still some particles I can't explain.

Being a senior, I do not know how to see Rich's "senior moment". Plenty of seniors about here that keep their grey cells alive and kicking butt. I'd rather call it brain fart, obnoxia, or whatever.

The pump can handle the internal screen and an external filter. No need to remove the screen. With an external filter you shouldn't need to go inside the carb to clean the screen. That's the major benefit. That's why I just recently installed an external filter a few inches from the tank. I can get at it by simply removing the canopy. Probably only need to clean the screen every year or two for rebuilds...if that.

There have been several articles published in the last few issues of M.A.N. and Model Aviation that have provided some absolutely terrible advice regarding gas engines. It reached the point a month or so back that one can only think that the people writing the articles have never seen a gas engine, let alone used one. That includes the article where they "bench tested" an RCS 50. They couldn't even use props considered "standards" for the engine size.

My advice, everything you read regarding gas engines in the two most popular R/C mags should be ignored or viewed as meaningless tripe.

Use an external filter or two. One in the plane and one in the gas can. Keep the screen filter and clean it once in awhile. New Walbro carbs have membrane components rated to 10% ethanol/methanol. Buy a carb rebuild kit and use it once a year or so. Old Walbro carbs might benefit from the installation of a rebuilt kit if it has older, ethanol sensitive membranes. If you can learn how to tune a carb you won't have a problem.

I wholeheartedly agree. Too many things are written nowadays that are just plain BS, confusing the ignorant that seek to broaden their horizon. It is a good thing that questions are posted here.
This question seems to have but one answer by all who responded. Leave the screen in place. It is the carb's last defense line.

There's your answer.

Is it wise to run an external filter? Absolutely. I run a filter in my gas can, so the gas is filtered before it ever leaves the can and heads towards my plane. I run felt clunks, so there's a filter in the tank. And I run a filter in-line between the tank and the carb.

I always run a 3-line tank, so I never force fuel BACKWARDS through my felt clunk to fill. I fill through the 3rd line. Fuel gets filtered before it leaves the can and goes straight into the tank via the fill line. It then gets filtered by the felt clunk on the way out of the tank. And it passes through the external in-line filter before it enters the carb.

I've never taken a carb a-part and found so much as a SPEK of crud in one of the screens. Gosh, I wonder why?

I am too! Brain fart might have be better, but CL has been living the glory days of the '70 for a long time, I always liked Peter Chin's advice or reports better anyway.

Like you I now use a three line system in all my gas models but forego the use of an external filter, but my fuel is filtered four times before it reaches the carb. First off there is a felt filter on the fuel jug's pickup line, an automotive filter in the delivery line from the manual fuel pump, and felt filtered clunks on the fill and feed in tank lines. So far very clean carb screens.

Karol

I use a three line system with extensive filtering in all my applications, glow or gas. Too many problems are related to not keeping the needles and jets absolutely clean. It took me some years to find out there was no alternative for a three line system though.
On board filter in fill line, plugged for flight. Fuel flows only one way through the filter.
filter in fueling line. Fuel flows only one way through the filter.
filter in clunk pickup. Fuel flows only one way through the filter.
I strain all fuel entering my fueling jug. Fuel flows only one way through the strainer.

Our gas carbs are so very unforgiving when it comes to dirty fuel that it makes sense to filter, filter, filter filter.

Karol

Seems to me there's a whole bunch of hand wringing and 'debate" over this (I've heard it recently at the field as well) that is simply unnecessary.

How about just using gas with no ethanol??? Better performance, higher efficiency, and any concerns about the effect of ethanol on fuel system components is eliminated.

It's not difficult to find at all. Citgo stations are, ime, the best bet, as they are generally locally owned and operated, and thus have a choice of providing ethanol-free gasoline. Other companies' stations might as well, but Citgo seems to be the most common to do so.

Too much ado about nuthin'. Tune 'em right and any performance difference is undetectable. I don't get significantly more performance out of an engine running VP racing 100 octane racing fuel than I do 87LL.

You won't find any gas stations WITHOUT ethanol in the fuel at 6000' elevation. They all carry it with 10% in the fuel at a minimum.

It's rapidly becoming a national standard.

No thanks. I'd rather spend $10 on a carb kit than send $1 to Chavez. [:@]

You're wrong, but ok. I BOUGHT ethanol free fuel at better than 7,000' during a trip in March.

I readily admit there may not be any in your area. Don't live there, haven't traveled through there in decades, wouldn't have a clue.

we in Holland have national law to add 10% "bio fuel" to the concoctions the oil firms sell. That 10% probably is a mix of some methanol, and mostly ethanol, as that requires the least process control.

I don't understand. My weedeater has a Walbro carb on it. I bought in 1990 and today it will crank on the second pull and runs as good as it did new. I have used it at least twice a week every Summer for nearly 19 years. I have never cleaned a screen, touched the needle valves or done anything to the carb. I don't filter the fuel. I mix it in an old plastic jug and pour it straight in the tank. It might have an inline filter somewhere on it, but if it does I have never cleaned it either. I don't know if I have run ethanol mixed gas or not. I'd say I probably have. I never thought about it.
So why if we take basically the same engine and carb and put it in an airplane we now have to baby it and filter, filter, clean screens and worry about the kind of gas we use etc. Makes no sense to me.
Bill

study the fuel system. That will answer your question.
There are NO T-lines
There is a sintered clunk for sure
And yes, I have worked on several saws that stopped working because of carb issues, be it clogged internals, or failing membrane sets.
The problem with plane engines is, that you take all the good stuff out, and "forget" to put them back in.

Your weedie has a filter inside the gas tank, and a filter screen inside the carb. Same as our gas flying engines. You brought up a point so many seem to forget. Our yard equipment engines and our flying engines are not significantly different. In reality, the only differences are in the size and shapes.