OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Hand and Power Tolls Power Tools Shindaiwa concrete saw

Hi, am having carby problems with my concrete saw. It has a walbro carby, it has HDA 189B stamped on the side. Problem is unable to get fuel primed through the carby, have put primer hose into fuel tank hose and get fuel so i know its not the primer. Have put a new kit through carby as well as a thorough clean ( was needed ) but when fuel line and primer line are both hooked up to carby the fuel wont come through, seems to be sucking air from somewhere but cant figure out where. Any help appreciated Paul.

Hi Paul, can you tell us the model of Shindaiwa concrete saw please, and post a couple of pictures?

I'm not clear on what you are saying here. From the symptoms, it sounds as if you may have reversed the connections of the hoses running to the carburetor. In the basic HDA, there are only two hoses: fuel supply and crankcase pulse hoses. If you reversed these, the primer bulb sucks air from inside the crankcase instead of sucking fuel. See diagram:


Because your HDA sounds as if it has an air purge pump, you may have three hoses (fuel, crankcase pulse, and air return) or the crankcase pulse connection might be directly through the carburetor mounting flange. The same potential problem applies though: if you interchange the fuel supply and return hoses, no fuel will be picked up from inside the tank, because the fuel return hose is positioned above the level of fuel in the tank, so the only thing it can suck (if inadvertently connected to the fuel connection on the carburetor) is air.

Hi Grumpy. ( still unable to upload photos due to previuos problems, Bruce is still looking into it) The saw is a Shindiawa EC7600. Havent reversed the hoses as they are of different sizes and a primer can only work one way. The carby I have got is similar to the picture you supplied but it has 4 hose connections on it, one on top which goes to the crankcase, one on the bottom which goes up to the air filter casing, one for fuel in and one for fuel out to primer. Try to explain whats happening a bit clearer. Connect fuel hose to inlet on carby and primer hose to carby, pump, get no fuel. Connect fuel hose directly to primer hose,no carby, and get fuel within a few pumps... There are no air leaks or split hoses to be found.

I don't understand your description of the hose arrangements, Paul. I think we are going to need pictures that show the four hoses, how they connect to the carburetor, and where they go to. If you can't get Firefox to work for picture uploads, perhaps one of the other browsers will work better. Alternatively, you could upload your pictures to one of the photo-storage sites and post the references here.

Are you sure you used the correct kit for your overhaul? It appears you need a D20-HDA kit.

Did you follow the manual precisely when you overhauled the carburetor? Here is the manual:
http://www.walbro.com/media/21886/HDAseries.pdf

Hi Grumpy have posted a photo in the photo gallery section under my name. I hope I have all the hoses connected right but here goes. The top one goes to the crankcase, the black left hand side one is fuel in, the small brass one left hand side goes to primer, and the bottom one goes to air filter casing. (correct me if I'm wrong). I'll try to explain again. Connect fuel hose to black inlet and primer hose to brass outlet and pump primer, no fuel comes through, only to top of carby. Take hoses off and join together and pump primer, have fuel within two to three pumps. Carby is clean inside and out, got the right carby kit. Am able to blow air through carby with bottom removed and moving needle in and out with my finger, cant understand why fuel wont go through.

The photo is only 120 pixels wide, Paul, the file is only 3 kB and each pixel looks like a golf-ball on the screen. Can you post a higher definition version please?

I haven't yet found an illustration of that variant of the HDA carburetor that could tell me what is happening. The process for getting a 4-hose system working without a manual, is likely to take quite a while.

You might take a look at this 4-hose system on an HDA carburetor much the same as yours:
http://www.abbysguide.com/ope/discussions/65496-0-1.html

Hi Grumpy have put some hopefully clearer pictures in the photo gallery, sorry took so long been flat out last coulpe of days, no time to scratch.

Paul, I think the next mission is to identify specifically, what each of the four hose connections (pictured in the coloured ovals) does.

Hi Grumpy. Here goes: BLUE CIRCLE:hose goes to crankcase. YELLOW CIRCLE: fuel inlet. GREEN CIRCLE:goes to primer. RED CIRCLE:goes to air filter casing.

I don't understand those connections, Paul. If that is an air purge system, rather than an old-fashioned primer, there has to be a fuel return hose going to the fuel tank. How many hoses come out of your fuel tank? Where do they go?

If those connections you listed are correct, then for sorting out the primer problem, you do not need to connect the blue circle or red circle hoses: they are just open at the far end anyway when the engine is not running. That means you only have two hoses to find homes for. Suppose for a moment that you have those two correct: green circle to primer and yellow circle to the fuel suction line. When you push the primer and release it, fuel would be sucked up through the hose that terminates in the submerged filter in the tank, if those two hoses are correctly identified and there is nothing wrong inside the carburetor or primer.

Hi Grumpy, there are three hoses coming out of fuel tank. There is one which is a breather hose, one that connects to fuel inlet ( yellow circle ), and the last one is the return from primer. Will give what you suggest a go, only the two hoses, will let you know what happens.

Thanks Paul. If there is no suction on the port you connect the fuel inlet hose to, either it is the wrong port, or there is a horrendous air leak inside the carburetor. Then you just check the other ports to see if any of them has suction: if one of them does, that is the correct fuel inlet port. Of course you don't even need to connect the return hose if there is no suction on the inlet port, since it isn't going to pump fuel anyway.

Hi Grumpy, Have done as you suggested and also doubled checked the ports for my own peace of mind and guess what there's an air leak. I was able to hear it when I put my ear next to carby. Now i need to suss out where it is and why its happening, or is the carby just stuffed???

It's quite unlikely that the carburetor is physically damaged, Paul. The most likely places for a large air leak to occur, are between one of the diaphragms (fuel pump or metering) and the outside air. I suggest you check whether there is a wrinkle, or perhaps you've missed locating a diaphragm on one of the retaining pins, or there is a piece of dirt or old diaphragm on a sealing surface, or even the diaphragm itself is perforated. It is less likely you'd be able to hear an internal leak, such as a non-seating metering needle. Nevertheless, if you are opening the two chambers you should pay careful attention to the flap valves.

I would double check to make sure you have the gasket and diaphragm in the right position. Gasket against carby body on metering side, and diaphragm against carby body on the pump side.

Good point, I belatedly thought of that overnight - it's a common mistake. If you put the gasket on the wrong side of the diaphragm, the flap valves won't close. I'm not sure that would result in an audible air leak, but it would keep it from starting, and perhaps from pumping air through the bulb pump.

I accidently did it once on a Partner K700 brick saw. It had no primer, but it started and ran ok, but would cut out when hot and start when it cooled down. After hours of checking coils, barrel and piston, air leaks, tank breathers etc. found out it was my stuff up, one which I have never made again.

Thanks for that report Tim. Probably through dumb luck I've never done it, and have had no real feel for whether the flap valves would manage to close despite the large gap. From what you say, it sounds as if (with that fairly large engine, and correspondingly large crankcase pressure pulses) they managed to close at cranking speed, but the faster the engine ran, the less time they had to close across the large gap.

The easiest way to go is to follow the manual blindly until you've done the job so many times that you do it correctly by sheer habit.

Hi Grumpy & Tim, I have checked out all gaskets and diaphragms all seem good. The flap valves are nice and flat their not bent or damaged in any way. Main diaphragm is good, all locating pins are lining up. Should I get another kit and start over again?? When I suck through primer connection with my finger covering fuel inlet I can hear the diaphragm working but sucking air as well? So am I correct in thinking that the diaphragm and or gasket are no good and need to be replaced again?(just thinking this way as I have brought new spark plugs that were no good, maybe this kit was no good???)

Paul, I've had bad diaphragms in cheap kits but I haven't had them look perfect even on close inspection, but not work. What I have had, is multi-purpose kits with diaphragms that look almost right but will not work in my carburetor. In particular, the fuel pump diaphragms for Walbro WA and WT carburetors have differences in the flap valve placement but otherwise seem to fit. The way you detect this problem is to compare the new diaphragm very carefully with the original one. I suggest you do that with your HDA kit: there are several different HDA models.