I'm running out of ideas for getting my BME50 to operate reliably, and I need some outside opinions. Here's the situation:

I've been running this engine for about 6 gal. now and have yet to get completely confident with it. Today I thought for sure the problem was solved, but I was wrong. First two flights the engine fired right up, idled smooth (as can be expected), transitioned instantly and made tons of power for both flights. Third time I fired it up it wouldn't come off idle without gagging and trying to quit. So I opened the low needle a little and everything was fine. Now I never changed the needles after the first two flights, so why should I need to now.

Here's the real trouble. Since I purchased the engine, it has behaved strangely like this. Sometimes changing the needle works sometimes not. So I started checking for other reasons. I checked the fuel tank and lines for dirt, bad fuel lines and looked for air bubbles when the engine was running. No problems. I checked the carb. filter (walbro), and flushed the entire carb with clean fuel. No problems. I checked the plug gap and electrode color. Everything as it should be. I checked the ignition battery, switch and related wiring. No problems. I even pulled the engine and ran it on the bench to see if vibration was causing problems. The engine ran perfectly fine on the bench, didn't take any fits. So I thought maybe I needed to mount the ignition box in a way that would reduce the vibration. Put the engine back on the plane, mounted the ignition module in new foam rubber and strapped it down good. Fired the plane up today and thought my worries were over, wrong. Third time I started it the problem returned. I'm at a loss, any advise would be very much appreciated!

Ben

Here's a long shot (since you didn't say what oil you were using). I had a similar problem with my Brison 3.2. Turns out it was the synthetic oil coming out of solution and coating the carb passages making it a little leaner each flight until you just couldn't get it to work. Went back to non synthetic oil and all problems disappeared. Seems that the oil doesn't mix well with SF Bay Area blend of "clean" gas. You can see the thread on that here - http://www.rcuniverse.com/showthread...hreadid=117976

Good luck.

Halll

I'd call Keith at BME, tell him your tale, and ask him to send another carb. My money is on the carb being the problem....

I did forget to mention that I have been running amsoil 50:1. We don't have "clean" gas around here and I've used amsoil in other 2-strokes w/o problems. I'll probably mix up a batch of non-synthetic, just to be sure I don't leave any stone unturned. Can you recommend a quality oil?

I was planning on calling BME this week and see if I could get some help. To me the problem seems to random to be mechanical. I was thinking that maybe the ignition module could have a problem. I'll make a few calls this week and see what I can come up with.

Thanks for the suggestions, keep'em coming.

Ben

Valvoline 2-Stroke works for me. I did try Amsoil at 100:1 a few months back (I really do like synthetics) but had similar results to my Klotz experience. It's our gas!

Hall

I read a thread where a guy had similar problems and after all he went through including buying anothe CH ignition it turs out that the problem was a bad switch. Make sure you are using a good one to connect your ignition to your battery

How about, heat. Are you getting enough cooling when it is in the plane.
How long between flights,?.

I read the thread about the bad switch also. When I had the plane on the bench, I tried the switch I had in the plane, 2 others, and several battery packs. All worked fine.

I thought about heat as well. I don't have a temp. gun, but I had about 20 min. between flights, so the engine should have been cool before restarting. Also, the engine didn't sag or give any indications of overheating during the flights.

When I first started noticing the problem, I was seing it in flight, so I thought it had to do with airflow affecting the carb. I tried the tube over the carb. pump vent with fuel tubing into the fuse idea. No help. I also tried a velocity stack in every orientation with no luck.

After Gilcon's post I was trying to remember if I had the problems when I was using non-synthetic oil for break-in. I'm pretty sure I didn't, so I'm going to switch back to non-synthetic and see if I get the same issues.

I'll let you know how it goes.

Ben

bdphil

If you're going to try the petroleum oil, make sure to note your needle settings and then pull them out and spray carb cleaner thru their passages. That will remove any build up of oil. Also that will work with the synthetic (if that's your problem) for a while, but the symptoms will return.

Hall

about the running problem. Does it on sag for the first 30 to 60 seconds after start up, has it gave you any problems in the air or is just after first starting and the clears up. If this is the case let me know I might have your answer.
Brian

Walbro carbs have a very fine internal fuel screen. It sounds like a piece of trash made it past this screen and is playing havoc with the fuel inlet needle seating. Either that or it's plugged. If you have some time, disassemble the carb and check for dirt in the passageways and especially around the fuel inlet needle. Clean the screen and try it again.

Rein

BrianB,

I only have problems in the air if I can't get it right on the ground. At first I thought it was only happening in the air, but I soon realized that it was exactly the same on the ground. Sometimes it just won't come off idle without richening up the low end needle and sometimes it works perfectly. What were you thinking the problem could be?

Rein,

I have had carb apart recently and there were a few small specks of dirt so I cleaned the screen, removed the needles and flushed it pretty good. Then I changed the filter, fuel lines and rinsed the tank. It shouldn't be dirt, but I'm going to have another look.

It it starting to sound like a problem with the carb.. Either dirt or the oil thing. I'll solve this problem one way or another!

Thanks for all the advise.

Ben

You're trying to solve one problem and end up creating more. I disassembled the carb. and was using the compressor to try and clean it out good and whoops there goes the screen. Forgot to remove that darn thing. Needle in a haystack doesn't begin to describe finding that thing in my shop. Well, off to find someone in town who has one available.

Ben

what a bummer. I got one from a local mower shop. No problem. You really need to call BME about this problem. Also. Do you have an inline or pickup fuel filter installed?

Ben, Let me offer my 2 cents worth.. First. I worked for Homelite Chain saws for 10 years on the bench and running a service center. (Just wanted to give you my back ground). Now about your problem... As far as cleaning your carb is concerned.. you can't really do that unless you remove the Welch plugs which cover the small passages in side the carb body. Its possible.. but not likely .. that something there is floating around. I say not likely because if it were dirt were in suspension and then covered one of the small outlets.. your engine would go leaner. The Inlet Needle valve could be sticking once in a while. That is the needle which allows fuel to transfer from the pump side of the Carb to the discharge, regulated side of the carb. If this needle is sticking and not closing when it should it would cause a rich condition.
I don't know how good their ignition is but usually they either work or they don't. If its intermitent you can hear the engine missfiring . I have doubts about Syn oil being a problem inside the carb.. When I was doing Chain saw testing in our engineering lab we ran saws every day on normal oil and then we changed to Synthetic to cut down on the smoke in the lab. Did not effect any of the saws which represented over 35 different makes and models. My suggestion is if you cannot get your engine to run consistantly after all your tinkering.. send it back to Keith for a look.. I know this really doesn't answer your question but hopefully it'll give you a little more insight.. Regards BobH.

I have a pickup filter in my gas can and an inline filter between the tank and carb. in the plane.

The only reason I haven't sent the engine in is because I ran the engine on the bench several times and it worked perfect. I know if I send it to BME it'll run perfect for them and it'll come back with a clean bill of health.

I don't know why It only shows up on the plane, there's nothing different other than I only ran it once or twice on the bench.

Anyone having problems with their DA50?

Just kidding. Should I consider trying a different carb.? This one is a Walbro WT. As simple as a 2-stroke engine is, there can't be too many sources of problems (one would think).

Ben

Ben, Have you always had this problem?.. and I though you said that the problem was on the ground as well as in the air?.. your right about the 2stroke, not much going on mechanically with them.. you have air/fuel/ igniton. thats about it. If you have all 3.. it should work. Don't know if you took your carb off but in any event.. you can check the pulse hole in the gasket and spacer to make sure its lined up with the hole in the carb. Sounds like it should be but ?? The odd thing about your situation is that your engine begins to run rich and thats not normally the failure mode. I wouldn't be surprised if its the inlet needle/metering diaphram. You could check to see if the inlet needle is doing its job by putting 5-7pressure lbs into the fuel line and see if it holds, It shouldnt be leaking. Regards BobH.

Just retired and closed my small motor shop after 35 yrs. I agree with BobH. There are three holes under the welsh plug on the engine side. If one hole were blocked with a piece of turf, it would make it run lean. If you punch out the welsh plugs they may not warranty it so check first. Could be an aluminum chip right from the factory.

bdphil,

Your scenario describes what I have been through myself to a "T"
Remember to keep it simple. at least I have hard time with it.
According to laws of physics If you get the needles set and nothing changes, then neither should the needles. But then there is murphy's law, if it can it will. What i have found ,if i set the needles where everthing is just fine, transition and all,
go ahead and set the high side another1/16 or so richer to
help with the sag during transition. I know if it its set for for a couple times and been flown it shoudln't be the needles.
If these carbs had just a little bit of an accelerator pump ,
boy that would be nice. The other thing I have done and learned from others of the same concern is to mix a little negative curve in your throttle expo to help slow the throw during transition.
And the other thing it helps in ,if you have noticed at a little above 3/4 throttle you don't really have an rpm increase when given the rest of the trhottle is moved up, this will also help in giving a true linear response throughout the whole range.
do several upline full throttle runs listen carefully for any sagging
just make sure you are still not too lean on top end.
You may already know all of this, but this is what kept me from
loosing the rest of my hair.

Well I just got back from the lawn/garden place in town. They had the screen I lost and I asked them about the problem. They looked it all over and said it felt like the little flappers (I don't know the exact term for the components carbs. aren't my best subject) on the fuel inlet side seemed pretty stiff. They swapped out all the gaskets and related gear for new parts. Hopefully I'll get a chance to fire the engine up this week.

BobH,

Before I figured out that richening up the low end needle would sometimes solve the problem, I just flew it that way (first gasser, assumed it wasn't too big a deal). Then I had a dead stick and broke a set of carbon gear in the weeds so I started trying to locate the reason. When the engine has the issue it's from the time I start it. It's not like it's OK and then a few minutes later decides to act up. If I start it and it's working right, it stays that way. If I start it and it won't transition, it stays that way until I fiddle with the needle.

The guy at the mower shop seemed to know more than me (about that carb. anyway) so I'll assume the internals are correct. I'll fire it up hopefully tonight/tomorrow.

Ben

I have a Brison 3.2 that would lean out for no reason when in flight after I started to run synthetic oil after break in. Had the same problem bringing here in dead stick. Wheel pants caught on the high grass ripped off gear broke cowl and engine mount. So I went back to the sthil chainsaw oil non-synthetic 50/1 mix after I fixed the plane and motor has ran great ever since. It does sputter a little in the mid range on the 50/1 but never quits and the plug looks great so Iam sticking with it. Like I said not sure why but it seem this engine runs better on non-synthetic.

Ben, that flapper may have been the metering diaphragm I was talking about? Any way give it a try and see what happens.... There is the senario that says... one of your inlet holes is normally plugged ( under the welch plug) and you are adjusting your needles to compensate for that.... and when the debris floats out of the way... your rich.. A way to check is to look at your needle adjustments... they should be somewhere in the 1.5 turns out vacinity. If its a lot more.. that tells us something important. They may be less like 1.125 or so. thats ok.
Flypaper. Congrats on your retirement!!. Hopefully you can now just have fun!!
BTW after I left Homelite. I went to work for the USGovt. testing chain saws for their Kickback energy in an engineering lab.. where I still am lol!!!!!!
Regards BobH.

2LO;
I have a converted 60cc Homelite with a very old carb with an accelerator pump on it. Idles at smooth 2 stroke. Doesnt hesitate on acceleration at all. They should start making them again!!

I ran the engine a few times on the bench and everything was just fine. A few flips to bring the fuel up, turn the ignition and choke on, two flips til it pops, choke off, starts on the fourth flip every time. Idled great, instant transition, and ran up to full throttle just fine. Ran it a few minutes for each of 4 runs. No sign of the mysterious problem.

I guess I'll put it back in the plane and take her to the field and see what happens. If it gives me fits, maybe I'll try a different fuel. Thanks again for all the great advise!

BTW, I asked the guy at the lawn center if synthetic oil has been known to cause any problems for them and he never heard of probs. with it. But if something can cause problems, generally it will happen to me.

Ben

I forgot to mention, the low needle is a hair under 1.5 turns out and the high needle is a hair under 2 turns out. With the BME muffler it turns a 22-10 mejzlik at 7100 rpm's.

Ben