Yea I hear what you're saying but two perfect flights and then everthing goes south without warning? Runs good on the ground but not it the air? Things are not adding up.

You are so right TOM. I would have never thought to check on something like gaskets on a new engine. Especially a 3-w. I have used this engine for about 10 years with no problems. It just went from plane to plane. I have another 3-w a 100 and when I get time I may take a hard look at that engine too.
I too tell my customers to tune their new gas first before flying the plane. As you so rightly have pointed out to hear someone say "I have never needed to touch the needles" drives me up a wall. I can hear the burble in the air why can't they. I just keep my mouth shut unless they ask. To them the pop pop is normal.
When the kit come in and i get this plane in the air I'll report back, hopefully with good news. Dennis

To Tony, to be honest it did seem that I was down on power lately, but because this was a new plane all I wanted to do is fly. That is my fault. when something fells wrong you should stop and find out why. don't wait until everything goes south. Dennis

While you have the carb apart, check the fuel screen with a good magnifying glass.

I have seen a few screens on "well run" engines recently that looked clean to the naked eye but under a magnifier they have a clear crystalline buildup on them. That buildup moves easily enough with a "reverse flush" of Carb cleaner through the carb orifices. I have no idea what the buildup is - it isn't the normal dirt that we see and I suspect it is just some sort of precipitate from the fluids going through it over time, I have no idea when it starts to form or how long it takes to form - I have some theories but won't espouse them here yet as they are totaly unproven.

I'll give the screen a good cleaning. Dennis

Just got a call about a 3w-150 just back from a shop with a new ignition. Pops and floods but won't run. Looks like I have something to do Saturday after all...

aussiesteve,

In a life many years ago, I use to drive a gas tanker truck. It was not uncommon to get quite a buildup of what looked like a very fine, clear silica sand in the bottom of the tank compartments. Yes, this material would have been downloaded to the underground storage tanks at a gas station and in those days, there was no final filter in the hose before the nozzle that goes into the vehicle .... so it would have been passed on to the vehicle tanks in some quantity. Maybe something like that could be happening these days and if so, maybe that fine material is what you are seeing in the screens.

I never could understand where that material came from but it had to come from the pipeline facility I loaded out of.

ivae had issue like that doin my high end.... on the ground it never skips a beat, in the air wot doing a fast flybye tthe engine will skip a beat... i land, then go in a little on the high till it goes away.... the best thing i have found is lean in the groung with engine running and find the peak till it loses rpm then back out to peak and a hair more and yur good to go....

Consider the positioning of the diaphragm pulse opening. If it's facing a forward or nearly forward orientation it will see little impact, or compressibility, pressure on the ground. It will be subjected to quite a bit more in forward flight. Perhaps more than it can compensate for.

Carbs in anything can be working fine today and not work tomorrow. It's called wear and when they have worn enough they cease functioning as they should. Accellerator pumps were really good for that.

I do run a line into the fush from the carb. Dennis

Since I'm rebuilding the carb I decided to upgrade the carb mounting block. I had already got the metal reed cage and now will have a metal carb block from AI
http://www.aircraftinternational.com...7/Default.aspx

Usually the carb mounting block is used to isolate the carburetor from the heat of the engine. I don't know if this applies to your engine. A metal one may not be the right choice. Check with the pros who are watching this thread. Dan.

3w shifted to metal risers about 2 years ago to eliminate leaking insulators. The metal version is now what they use.

TOM, Thanks for the update. Dan.

since I'm doing all this stuff to the engine, I figure I'll change the plugs. what is the gap setting on CM-6? Dennis

The plugs are standard set to 0.5mm (0.020" ) DA wants slightly less (0.018" )
I use RCexl iridium tipped plugs, set to 0.022" (MVVS engines)

Since we're into carbs again at the moment I'd like to bring up the sticky at the top of the page with all the good set up info. It's throttle linkage again and those that have throttles using a lot of expo or mixes need to go there. What brings this up is two planes in the last two days.

One was a 35% that had the throttle servo binding so bad from excessive travel it snapped the servo output shaft clean in half on a JR high voltage servo. The owner was wondering why engine RPM was cycling up and down in flight... That was a dumb way to ruin a very expensive servo. Not to mention no throttle ever needs a servo that fast.

The second was a 40% today where the throttle stick was REAL sensitive. Got inside the cowl and saw the rod was connected at the outside lever points at each end of the servo. Checking the travel adjust at the transmitter showed the travels had been dialed back to about +/- 40% travel to make it work. Twitchy throttle response with a little stick making big changes. Spent a little time moving the throttle connect at the servo to the inside and left the carb end alone at the outside. When all was said and done the travel adjust was 100%-100% open to close and no mix needed anymore. The throttle trim was now effective for setting a great idle and for starting and shutting down the engine. Could not do that prior.

Things like that mostly are (for 90%) the cause of setup problems.

Hi Tom and Friends, Need some help. I have been adjusting and rebuilding Walbro Carbs for years. Recently my Trusty "Pop-Off" unit #500-505 would not hold pressure. Walbro does not have a rebuild kit for the unit. A new one from Walbro is listed for over $200. I found a distributor that will sell a new one for $80. All I need is the flapper valve. Does anybody have a solution for me. Thanks, Col Chuck Winter

Colonel,

I think you're going to be out the $80.00. I have never personally seen replacement parts for the gauge.

I would be trying to make a replacement out of a piece of inner tube or something...

AV8TOR

I use a smoke pump check valve, and bike tire pump. The whole assy is built up of used parts.
A bike tire valve would be an excellent check valve as well.

Might just need to replace the O-ring. Had to do that in mone. The replacement O-ring came out of some standard O-ring selection kit.

Try this...soak the rubber part with silicone spray or armor -all. Do what it takes to get it clean and supple again. It may all of a sudden start working again! Capt,n

Ok, here's my request for help from T.O.M..

I have a 7 ft. sleeper couch, 6 foot chest freezer, large armior, and walk in gun safe that I need help unloading and positioning this Saturday around noon. What a ya say......buddy?