Mitsu1

My Feedback: (13)

I've got an RCGF 100cc Rear Induction engine and I've been having a terrible time getting fuel from the tank to the engine. I can't manage to get any fuel up the line at all. If I spray fuel into the carb, it starts right up and runs until this is burnt off. I can't see any fuel move up the line during running or during choking. I first, carefully rebuilt the tank to no avail. Then I moved on to the carb. Noticed the carb attach bolt on the side nearest the throttle arm to be stripped, and will not tighten down. The other side tightens up just fine. Carb Insulator block seems to be just plastic, and the fine thread bolt simply stripped the threads out of the block when assembled at factory I guess. Fuel pull up was hard from first day, but now is not possible after sitting up for nearly a year. I removed the carb and also noted the gasket seal compund on the gasket did not completely surround the bolt hole of the gasket. I've tried but have had little luck in locating a source (Other than the factory in China), for a replacement insulator block. I'd like to just repair the threads in this one somehow. Is there a reliable method other than tapping and installing threaded brass inserts?

Mitsu1

My Feedback: (13)

Some other things I also did in searching for why I can't draw fuel up to the carb was to pull the plate off the carb where the pulse line comes in. I was able to verify no obstruction in the line through the nipple and to the diaphram by blowing through this line easily. The screen was perfectly clear as well. I also attached a line to the pulse nipple on the crankcase and blew through it with no obstruction. I removed both needles and blew through them, as well as the fuel inlet nipple.

av8tor1977

My Feedback: (6)

Well, here is something you can try, but it may or may not work. Fill the hole with epoxy, being careful to actually get it full and not have air bubbles in the epoxy, and make sure the hole is perfectly clean first. Then drill and tap the epoxy after it has cured for 24 hours. Then what I would do is make a stud to use in that hole instead of a bolt. Coat the threads of the stud with epoxy, and screw it in. Once again let it sit 24 hours, then mount your carb with a new gasket. I don't recommend gasket sealer on carb gaskets. Just make a new gasket, soak it in some oil or coat it with vaseline to soften it, and carefully bolt your carb back on.

It might work... probably worth a try as it will cost basically nothing. Meanwhile, order a new part.

AV8TOR

jedijody

My Feedback: (1)

Heli-Coil inserts work well in plastic as well.

soarrich

My Feedback: (98)

Something like this will work, but you want 10/32,5mm work in them. HomeDepot should have them.

http://www3.towerhobbies.com/cgi-bin...&I=LXE070&P=SM

Mitsu1

My Feedback: (13)

Ok, I bought Du Bro 10-32 threaded inserts and a 10-32 socket head screw (The original screw threads wouldn't work with the 10-32 insert). This looks like the best chance for lasting success. I'll have to be careful when drilling out for the insert since there won't be much outside wall left. But my question is this, Is this likely the reason I couldn't pull any gas up the line, even when the engine would run 3 seconds sometimes before it would burn off what I squirted into it? I mean, the stripped screw had a "little" tension when turned, just would not tighten and snug up. Would a leak this slight stop the carb from being able to move the fuel at all?

Tired Old Man

My Feedback: (1)

You mentioned that the engine/carb had been sitting for extended periods of time. Often a situation occurs when carbs are left sitting the the internal diaphragms dry out. This becomes a real problem at the pump/check valve diaphragm. If they are dry the carb wil lnot draw fule regardless of how much gas you squirt into the venturi. The solution can go one of two ways. The first is to rebuild the carb using new diaphragms. The secone is to disasssemble the carb and wte the diaphragms with fuel and reassemble. They generally work on their own from there if they were not completely dried out, carcked, or deformed.

This has happened many times with engines that have sat for awhile, and it's quite common with new engines that were manufacturered, test run, then set on a shelf awaiting sale.

Mitsu1

My Feedback: (13)

Thanks Pat, I'll be sure to disassemble and wet the diaphram before I put it all back together. I had a friend ask me if I stored it wet or dry. When it was last flown I didn't know it would sit for 11 months, so it was flown, then shut down by idle trim and tank was drained as normal. Then of course life got busy, and nearly a year passed before I got around to flying this particular plane again.

aussiesteve

Yes - this is a common RCGF problem.
I know - I worked hard trying to convince the factory to install the metal thread inserts at production - I believe they do it now on some models.

Also check the insulator block for flatness - you will probably find that the carb mounting face is not flat - another known issue with them. take a flat surface (I use a piece of plate glass) put some sandpaper on it (I use 320 grit wet and dry) and gently sand the face until it is flat.

Back when the factory was talking to me and I used to sell their product, I used to take the carb blocks off, sand the faces flat and install helicoils before any engine ever went to a customer - I learnt the need for this the hard way of course.
Helicoils are good for a couple of reasons - the main one being they are quite thin walled and don't reduce the wall thickness very much.

Depending on the age of the engine - also check the pulse line from the crankcase to the carb - earlier ones had a real crappy quality of line and it may have a crack in it.

Your other priming issue could be to do with the bleed hole in the choke butterfly. Depending on which carb you have (they have used a couple of different ones) you may have a bleed hole in the choke butterfly - solder it up. The other carb they use (I don't remember the models off the top of my head) has a notch on the side of the butterfly - not much you can do there - not easily anyway. on those, you may just have to accept that a fuel shot into the carb opening is the best way to prime at the beginning of the day.

Mitsu1

My Feedback: (13)

Yes, Steve I've heard about the insulator block flatness issue. This is one of the updated engines, but not the new "B" series they now have. This engine was returned to the factory and fitted with a new crankshaft, hub assembly, two new cylinders and the newer rotated carb block and reeds. It ran exceptionally well and powerful, with the only issue I had being a "skip" when a quick roll was performed. I suspect that was related to the leak at the carb block. I'll be sure to replace that blue tubing pulse line to be safe. I'll look into helicoils. I have the EMAS carb with the notch on one side of the butterfly.

rodney tanner

I had exactly the same problem with mine.

I tried the DuBro inserts and but never got the block properly flat and sealed. Henry/Piston sent me a replacement that did not line up to the carb properly - which must have restricted the WOT performance, although the facrory said it would'nt make any difference. My solution was to use silicon gasket with the old gasket, pleanty of lock-tight, carefully tighten down the carb bolts and accept that this was the best it was going to be. That worked fine for the time I used it - about 30 gals. First start always took about 30 flips to prime the carb.

Mitsu1

My Feedback: (13)

Success! Well, I had several things as the possible culprit to my carb problems and I'm not totally sure which one I fixed, but here's what I did. I had to pull the engine off to get to the carb and insulator block. First I carefully enlarged the carb attachment bolt holes of the insulator block and screwed in Du Bro 10-32 thread brass inserts. I pulled both plates off the carburetor, checked for anything foreign. I removed the pump's gasket, screen and diaphragm. I soaked the diaphragm in Koni Kroil (An Industrial penetrating oil I just happened to have nearby). I put a thin layer of Permatex Red Gasket Maker high temp RTV silicone to both sides of the factory gasket that connects the carb to insulator block. Bolted everything back together and mounted the carb, then replaced the cheaper blue pulse air tube from crankcase to carb pump with better yellow tygon tubing. I failed to do one thing that I really should have, and that was to seal off that half moon cutout that is standard on my Emas carburetor choke plate.

When all was ready to test, I tried pulling fuel up to the carb by closing the choke and flipping the prop several times. No luck! I then folded over a hand towel and pressed it tightly over the whole choke opening and was able to pull fuel up to the carb. Engine started and ran fine other than carb being out of tune. After the initial 'towel' choking, normal choking would pull fuel up to the carb easily without needing to cover the choke plate with anything. First flip starts from then on, but carb had a mid-range transition issue that I couldn't seem to tune out. I finally went inside and pulled up Mark Fuess' Walbro Tune Up Guide, http://tech.flygsw.org/walbro_tuneup.htm ... and was able to eliminate the midrange stumble one my second adjustment. Valuable tune up guide.

Mitsu1

My Feedback: (13)

%@$#!*&!~ .... Ok, ... INHALE ... now slowly EXHALE ... I don't know how much longer I can do this! After all the trouble I went through with the above outlined steps, and the complete success of last weekend, ... I am right back in the same boat, with no ideas left. I totally wasted a beautiful sunny day with temps in the 60's and a 5mph wind to this , this ... engine.

This thing is doing exactly the same as it was before the carb rebuild. When I got to the field and got everything assembled, I primed the carb and saw fuel reach the carb and puddle in the venturi that first time, but never again for the next 3 hours. As before, I could spray fuel into the venturi and it would start right up, but die as soon as that fuel was burned up. There was a bubble in the fuel line just before the carb and I was never able to get that bubble to move whatsoever. I tried everythihng I could image. I totally removed the inline filter and went straight to the carb and it still would not move fuel. I even connected my fuel jug to the plane's tank vent line, and pumped backward into the tank to force fuel up pickup line to the carb, watched fuel arrive at the carb, then started the engine and it still would not pump/pull fuel into the carb.

I'm so frustrated I don't know what to do. Does anyone know of a Walbro direct replacement for this Emas carb? I know it may still be the carb block, but I can't get one of those here by tomorrow, but I'm sure I can find a small engine shop with Walbro carburetors. It makes no sense to me why this thing peformed so beautifully last Sunday in my yard, then today reverted back to the same crap as before any work was done. The only thing that's changed to my knowledge is 5 days have past .

soarrich

My Feedback: (98)

Walbro SDC-80

BUT, that may not be your problem. These two strokes are simple, your problem is going to have a simple fix. I'd check two things, first put the pulse line off and put it in a glass of water, then flip the engine over, do you get bubbles? I'd also check the reed valves they may not be sealing, When you flip the engine do you get a pulse of air out the carb? You shouldn't.

aussiesteve

Way back when the factory responded to my correspondence, I used to oirder the engines with genuine Walbro carbs - I was charged $25 more per engine to get this "modification" for my engines

I think you may have also just discovered why I did that

There are a few sellers of engines that advertise "Walbro" as the carb that is fitted - many of the engines have got EMAS - there is a rumor that EMAS is a joint venture with walbro (I do not know if it is true or not) but there is a definite difference in the "primability" of the two brands. (If you bought your engine from a dealer who has adverised Walbro and supplied another brand of carb - send the engine back for a full refund - it's false advertising)

SDC80 and WJ71 are both good choices - if you know anyone with pretty much any 100 laying around, see if you can borrow their carb - there are a lot of choices that will work fine on that engine.

Mitsu1

My Feedback: (13)

Steve, I didn't get the engine from a dealer, I got the engine straight from Catherine & Johnny. It was one of the original engines, and it had probs. I sent it back and they repaired it with updates, replacing the crank, a larger hub assembly, the cylinders, the reeds, and the carb block. I got back the same carb (That I'm sure), the same mufflers and I believe the same case. I have had priming/draw problems from day one with this carb, even before it was repaired. Steve, one question ... I have a DLE 111 here and it has an Emas carb, but it does not rely on any pulse tube and has no such fitting on the carb. Does the carb block on this engine have the ability to supply pulse feed if using a carb without the pulse line?

aussiesteve

Hey mate
Cool - one of "Those" engines - yep - the originals sure did need those updates - good to see you had them done. It should be reasonable now at least. Catherine and Johnnnny are still dealers - just the most direct ones is all.

Unfortunatley, the carb blocks on them don't have the gallery necessary to run the internal pulse line. You could change over the cover from the Carb you have to the one from the DLE111 (I think they are probably the same basic carb model anyway) and it wil prove your carb issue for you at least.

The external pulse line is simply a tapping into the cover anyway. Just make sure the carb gasket blocks off the internal gallery on the carb mounting face - you definitley don't want both gallerys open at the same time.

Mitsu1

My Feedback: (13)

The pulse line from the crankcase is pushing air. I ran a line from the crankcase pulse nipple to a cup of water and it splashed it. I also put it up to my face and it is making a burst of air with each flip. So its putting air to the carb nipple. I also checked and the nipple through the plate is unobstructed. A note of interest, ... That nipple on the plate was detached and only hanging by the tubing when I got the engine from factory after the updates a year ago. I had pressed it back on but it popped right off again, so I pressed it again and glued it down with CA. That plastic nipple has a brass insert that presses into the carb plate. It's a relatively tight fit, so I really don't think it's the problem, nevertheless I'm popping it off, and pressing it again with silicone RTV to help seal it. Beyond that, I have no idea why it worked great, then doesn't work at all [&o].

aussiesteve

ah ha
I know exactly the fitting you mean. Try "re swaging" the brass pipe back on. It can be done with a centre punch inside the brass pipe. I used to take those fittings off if they were loose and tap a thread and insert a proper threaded fitting - some people use "JB Weld" to hold them in - it could be that fitting leaking that is giving you a part of the problem.

Mitsu1

My Feedback: (13)

Ok, I went through this carb again, well actually the entire fuel and delivery system. I did too much to name, but I now get the kind of reliable, easy priming that I should. Took the Yak out today and got in 3 strong performing flights. Didn't tach the 100, but it was unloading in the air great. No leaning out even with really long vertical pulls. Yak weighs 24 lbs, so I can say the engine makes good power.