Weird Walbro problem...
 

I ran into a strange problem with the carb on my Mac powered weedeater yesterday, and I thought I would share what I found with you guys. Maybe save someone some grief some day.

It had run a bit "ratty" the last time I used it, (months ago), so I figured I better clean/check the Walbro carb before using it again. So yesterday I pulled it apart and cleaned it. The regulator diaphragm was probably useable, but a touch stiff, so I put a new one in it. I did notice when removing the carb that one of the rubber fuel lines was like it was glued to the brass carb inlet tube, and came off in pieces. The hose itself seemed ok, but I had to scrape pieces of it off the tube where it had actually glued itself on.

I then put it on the machine and tried to prime it with the primer bulb. Most people don't understand how the primer bulb works. It actually pulls fuel through the carb, and squirts the excess back into the tank. When you use the bulb, you are not pushing fuel through the carb, you are drawing it through the carb. This causes the diaphragm to open, and fills all the passages in the carb with fuel. No fuel gets injected into the engine as many tend to think; all it does is fill the carb. Well, the carb wouldn't fill. I took off the primer and inlet hoses, and connected them together and the primer bulb itself was working fine. So I pulled the carb back off, and tore into it again. This time I noticed that the regulator metering lever was way low. So low that the diaphragm couldn't open the needle. I thought "that's strange, as I know I had it set right". So, I reset the lever height, put it all together, and tried again. Same darn problem; it wouldn't draw fuel through the carb. So I took it off AGAIN, and again found the metering lever bent down and far too low. That is when I reasoned that the needle valve itself had to be sticking in its seat. I had removed the needle when I cleaned the carb and it seemed fine. But upon examining the tip with a magnifying glass, I could see that the rubber tip was slightly swollen and actually sticky/gummy feeling. I cleaned the seat area again, put a new needle in, and then the carb primed perfectly. The machine then started on the second pull, and a slight tweak on each mixture needle had it running perfectly.

At first I thought it amazing that the primer could cause the metering lever to bend like that. But after some more thought, I realized that even if the primer only pulled .5 atmosphere, the diaphragm is nearly 1 inch square, so that would be around 7 lbs. of force pushing on the lever. The needle was stuck on it's seat and wouldn't move, so the lever bent.

It was a pain at the time as I wanted to finish and use the machine, but it was an interesting experience, and I hope this post helps keep someone from "tearing their hair out" with a similar problem some day. Apparently additives in the gas turned that rubber needle tip to "gumby", and caused it to stick so tight it wouldn't move. It would move when I grabbed it with a needle nose to remove and clean, but would then stick so tight the metering lever couldn't budge it!

AV8TOR

RE: Weird Walbro problem...
 

Interesting.
When I clean a carb, I rub the rubber needle tip with two stroke mix on a clean rag or paper towel. This usually gets all gum removed. I suppose it is the gum that caused the sticking?

RE: Weird Walbro problem...
 

Well, there wasn't any gum or residue. I had cleaned the needle with a squirt of carb cleaner like I always do, and lubed the interior of the carb with WD-40 like I always do. The actual rubber tip itself was deteriorated and sticky/gummy, and I failed to notice it. It really only showed up with a magnified examination and by poking at the rubber. You could poke it with a tooth pick or a probe, and it was just, well, "gummy"; soft and sticky. My first clue to the problem should have been when I removed the rubber fuel hose and it had "glued" itself to the fitting, literally....

I ran into a similar problem a few years ago investigating and repairing an ultralight airplane crash. The engine quit on take off and the resultant hard landing did quite a bit of damage. What I finally found was that all the ignition system wires that were bundled/tywrapped on the engine near the carb area had mushy insulation. You could squeeze the insulation and it would compress and come off in your hand, feeling all sticky and gummy. The tip of this needle valve in question was kind of like that.

AV8TOR

RE: Weird Walbro problem...
 

I think I read somewhere that Teflon tipped needles are available to keep this from happening. My guess is that the rubber tip of the needle was
and the tube to the inlet were affected by the ethanol that is now in most pump gas. So far we are able to get ethanol free gasoline from a nearby marina, but very few have this good gas. I run Coleman and Pennzoil in my G23 with very good results.

RE: Weird Walbro problem...
 

Im with you on the Coleman. the fuel additives in the Atlanta area are lethal to a lot of the carbs parts. Started using Coleman in my Gasser heli with a G231, has never seen gasoline. Has run like a Rolex from the get go. Super easy starting and very clean running, plus you can bring it into the house and the wife never even knows it there. Now all my gasser planks run it to. Its current cost is $7.99 at Wallyworld. Even at that Im still ahead on the savings on carb kits.

RE: Weird Walbro problem...
 

I'm in Mexico, and I don't know if they put ethanol in the gas or not. I don't know what they put in it... Apparently something that the carbs don't like! Never had problems with using it in my cars, not even my 450 horse 454 Blazer, though the octane is a bit low for that vehicle, just like it is in the states as well...

I use a mixture of Coleman fuel, Sta-bil, and 20 to 1 oil for a "storage fuel" for my airplanes as I was having a bunch of carb problems. I guess maybe I should use it in my yard equipment as well. I just can't bring myself to fly the Coleman fuel with it's octane rating of 50 to 60, though I have heard many stories such as yours about people flying it with good success.

AV8TOR

RE: Weird Walbro problem...
 

You mean this is all about a real weedie and NOT an airplane engine... Boy the bandwidth gods are going to get you.......

RE: Weird Walbro problem...
 

;)

AV8TOR

RE: Weird Walbro problem...
 

Nogales?

RE: Weird Walbro problem...
 

Puerto Penasco. (Rocky Point) 60 miles south of the border, about 220 miles due south of Phoenix, Az. Love it.

AV8TOR

RE: Weird Walbro problem...
 

Over 20 years ago my mother went out West with a neighbor lady who lived on the other side of the block that she used to work with.

They went to the other woman's - sister's house in Southern New Mexico south of Albuquerque off I25 among other places. She came back with all these stories about fishing in a little pond back up in the box canyon behind the house. She described all the details of the adobe type house and what a great time she had. I sure wish I could visit there.

When in the Army at Ft Hood Texas in the mid 60's I was roaming around the back areas and came up on a old house place that had been abandoned at least since the early 40's when the government bout the property. All that was left was the stone but to examine the homestead and try to evaluate what each building was and how life must have been there was a great experience. The ground was littered with steel jacket bullets.

I said Nogales because that is where the Interstate goes.

I'm sure you are enjoying it there especially as it is springtime yet.

RE: Weird Walbro problem...
 

It gets almost unbearably hot during July, August, and September, 100 degrees and 60% humidity, but the rest of the time the weather is perfect. The Sea of Cortez is great for swimming and scuba diving. The water gets to about 85 degrees in the summer. During the summer months everyone pretty much stays inside during the day if they are not in the water. It is great flying off the beaches! I really love living in Mexico. Maybe someday I can get my life arranged so that I can go further south to the mountains for the summer months, but other than that I wouldn't change a thing with my living situation.

I once drove around Tucson for almost half a day rounding up some things I needed. Fighting the traffic, etc. I decided then that it was much better to just order whatever I wanted/needed that I couldn't buy here locally on the internet and have it delivered. I have a mail service that brings the mail down here 3 days a week. I have an address and P.O. Box at the border, so I can receive postal packages, UPS, and/or FedEX. Works for me!

AV8TOR