flyerdave

My Feedback: (212)

Just got a nice DA100 for my Aeroworks Extra 300 and after several hours of getting everything set up, today I put in the fuel,choked it several times,and got it running within about five flips of the prop. It runs so sweet,(a little louder than I was expecting with the standard mufflers but I can always move up to cans or tuned pipe later). The only problem was when I pulled it down to idle,it would spit fuel out of the carb like crazy. Move the throttle up two or three clicks and the spitting will stop, but at idle it is just covering the front of the firewall at the bottom. Is this normal or do I have a problem? I can't imagine that this is normal for this engine. Thanks for the help.

Tired Old Man

My Feedback: (1)

Sounds like it's running pretty rich and needs tuned.

spaceworm

Some engines do this, an easy fix is to put intake venturis on the carbs You can get plastic ones for only a few dollars, aluminum ones cost more, or you can make your own. The venturis catch the spitting and then the next intake pulse sucks it back in. Fuel mileage goes up cause you are not wasting fuel, and the plane stays cleaner because the fuel is not blown all over. I guess the venture helps tune the intake pulse, but I am not sure how much if any performance is raised.

Sincerely, Richard/Club SAITO #635
"Always On, Slightly Off"

Tired Old Man

My Feedback: (1)

Some rear carb designs do this to a level viewed as a lot but most all carbs spit some fuel, especially when they are subjected to forward motion and exposed to the open air. Even with a velocity stack you encounter the venturi effect of moving air over an open tube, so total elimination of "spitting" is all but impossible.

New engines are not "factory tuned" and are likely to be quite rich in the lower RPM bands. The richer the condition the more excess fuel available to be pulled out of the carb throat. This requires user input to correct. Tune the engine, which is something every engine requires, and is also something that has been described in extreme detail a great many times in this and other forums.

Another condition that generates a lot of fuel blowback is worn or broken reeds, or reeds that fail to seat correctly on the cage frame. However, this is not something common to new engines and generally only seen with engines that have been in use for some period of time. A good general rule is that the better the engine the longer the reeds will remain functional. So it can be a bit brand specific.

One more item that can impact the amount of fuel departing the wrong side of a carb is the metering needle height inside the carb. Since carbs are now manufactured and assembled by cheap overseas or Mexican labor it's impossible to know if the carb was assembled correctly without performing a full carb teardown. With modern day outsourcing to foreign countries I see poor assemblies in as much as 50% of the carbs passing through my hands. I doubt even the best engine manufacturers get any better with current Walbro products. Can't say for Tillotson since they are based in Ireland and may use different manufacturing and assembly methods. The cloned Chinese carbs have a much higher error factor.

flyerdave

My Feedback: (212)

Okay,I have a report.
After running the engine again,the fuel spitting problem is no better.Something inside the carb must be wrong because I have leaned the low end needle almost to the stop and though I'm definitely no expert, I know this isn't right. I think I either need to remove the carb and have it rebuilt or send the complete engine to DA for a complete checkup.
The engine runs great, produces awsome power and from idle to full throttle, it transitions great. All of this really puzzles me,but I guess that is why I will never make a living working on small engines.

Can anyone tell me which walbro carb is on the DA100? It is not the DA100L, but the earlier version. Thanks

jedijody

My Feedback: (1)

Walbro WJ71

Tired Old Man

My Feedback: (1)

Revove the carb. Pull the diaphragm cover carefully by remvoing the screws. Check the button on the diaphram is engaged with the cover by lifiting one edge of the cover and sneaking a peak. Slide the cover away from the screw. Note how high the body of the needle is compared to the body of the carb. Adjust to sit even with the carb body by carefully bending the fork. Replace cobver and test run.

av8tor1977

My Feedback: (6)

And take a look at the reed valves while you have it apart.

AV8TOR

Tired Old Man

My Feedback: (1)

Reeds will be fine but the installation of the metering needle will be wrong.

av8tor1977

My Feedback: (6)

Why do you say that? A chipped or badly sealing reed valve would certainly lead to more reversion/standoff.

AV8TOR

Tired Old Man

My Feedback: (1)

If the engine is new reeds are highly unlikely. If the engine is less than a couple years old with occasional weekend use the reeds are not likely. If the engine is older than about 5 years, made before some reed changes occurred, there is a possibility of reeds being the problem. It won't hurt to check but I think it's elsewhere.

I'm going with percentages. Carbs are assembled by worker bees in China, Mexico, Taiwan, and Japan. The Mexico Walbros have been a problem since the first day there were assembled there. The China Walbros are assembled by what are likely some of the least experienced assembly teams on the planet. Taiwan a little better, with Japan at the top of the quality food chain. The room for carb assembly error is high, especially in two areas. One is correctly fitting the needle top to the diaphragm slot. The second is in bending the needle lift forks during fitting to the diaphragm cover, forcing the needle higher than it should be, creating a leaking needle seat.

flyerdave

My Feedback: (212)

Okay guys,
Because of my lack of faith in my ability to rebuild this carb. properly, I was able to purchase a new carb at a relatively good price.I took off the old carb.,mounted the new one and WOW!!! this engine is a dream with the new carb. There is no spitting,or dripping. I'm still working on getting the needles right but so far,it is almost like a new engine.I am dissappointed about one thing though. Because the carb was bought from a small engine shop and not DA, the fuel inlet nipple is pointed forward and is a smooth brass nipple instead of the barbed one. No big deal, I can live with it and just zip-tie the fuel line. At any rate, I am more anxious than ever to get this thing in the air. Thanks for the help.

av8tor1977

My Feedback: (6)

You can carefully grab that fuel nipple and rotate it where you want it, while maintaining inward pressure on it. Then you can pick up some "fuel barbs" from the hobby shop, and solder one onto the nipple.

I tie wrap my fuel lines even if they have barbs.

AV8TOR

mbinkley

I have a BME 115 that i got from Keith Baker. I was told is was an engine from the 2nd group of engines , it is about 4 or 5 years old. It is a littel drippy at the carb at idle.
I got the carb block fix from the nre guys at BME afew years ago.I also put a 90 deg snokel from 3W that helped some I think it just hold the fuel till the engine sucks it back on.
Do you think the reeds should be replaced. I have the carb set low end as low as I can to keep the engine running from low to high speed with no lag. I have a rebuild kit for the carb I will try that now.

Thanks for the help MB

flyerdave

My Feedback: (212)

Are you saying that the fuel nipple can be rotated without damaging the seal between the carb body and the brass nipple? Forgive my ignorance on this, but I thought the nipple was too tight a fit to be rotated by hand. Could heat applied to the carb body help any or is it not needed? Thanks for the help.

jedijody

My Feedback: (1)

Enlist a little helpfrom your trusty pair of pliers. Yes, it can be turned, it will not leak afterward.

daltonaviation

You can rotate the fitting or if you want contact me and I will send you a fitting that we put on the carbs to replace the brass one. And most likly the metering fork was disconnected on the original carb.

RTK

My Feedback: (1)

A carb should never drip, ever. The metering needle is staying open or not sealing properly, might not be engaged in the fork properly or miss adjusted, etc.