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

can you send a photo with the pump diaphragm and gasket laying in the right position on the carby with the end plate off, so I can see what they look like?

Hi Grumpy, sorry its been a couple of days been flat chat. Have gotten back to my carby and done some experimenting ( hope this sounds right). What i done was put some clean petrol into a dish fully submerging the carby all except fuel inlet ( yellow circle) and primer port (green circle) as well as held the the peice of hose above fuel. Then i got a straw connected to fuel inlet and blew quiet hard, no air bubbles anywhere, I then blew into the hose attached ( on the bottom of carby) pulsating as i done it (breathing in and out) and had air bubbles coming out of middle of carby. Am i right in guessing the main diaphragm has a hole in it even though i have gone over it a number of times and not found anything, even held up to the sun i still cant see any light coming through it. Have also done as you suggested and checked to see if there are any differencres in old parts to new parts, none at all, except the new ones look better. Will try to get photos up tommorow.

Paul, you said the fitting with the red circle, and the yellow hose attached, just goes to the air cleaner housing. That is unusual - my first guess would be it is just a vapour line, for emissions control reasons. Normally odd bits of vapour are just allowed to escape to atmosphere. Since I don't know where it goes inside the carburetor, I can't guess whether it is doing anything unusual. What does seem odd is that it would have a serious fuel hose and a pressure-tight fitting at the carburetor end, for a vent line. The fitting that looks as if it would be for a vent line is the one in the green circle, which is clearly not a pressure fitting.

So, at this point I still don't understand the plumbing on that machine.

Hi Grumpy sorry its been a couple of days. Have put some photos in the photo gallery for you to have a quick look at. Rechecked my carby throughly with a new diaphragm in it, believe it or not,still no go. Tried something different, put the carby onto an old chainsaw i got, only used fuel inlet hose and primer hose, it worked , third pull saw was going ,not perfect but going. So carby is "right" now,so whats going on now. Done a compression test, came up with 30psi. No thats not right,do it again,30psi. ( Tested a mower and came up with 115 psi, thinking mabey my tester had died, the week i've had it wouldnt of susprised me at all. Thankfully it wasnt. ) Started to strip the saw down and have a look at what i found. Well i think its time for the old girl to RIP. Thanks heaps for your help yet again Grumpy.
Thanks to you also timtoolman.

I agree with Tim's comment in Photo Gallery, it has most likely been run with no oil in the fuel. The only other possibilities that occur to me are if it became vastly lean while running and the operator went to full throttle to keep it running for an extended period (if it were anywhere near that lean it couldn't start I believe), or the ignition became retarded and the operator just held the throttle open to keep it running. I don't see either of those latter alternatives as being likely though.

If the cylinder bore is cast iron, it can be honed and fitted with a new oversize piston and rings. If it had a chrome bore it will require a new cylinder as well as piston and rings. If you can get a sensible price on the parts, it seems well worth fixing.

My guess is that the cylinder would be hard chrome plated, which the melted alloy can be cleaned off the hard chrome if the piston nips the cylinder. But this one looks like it has more stripes than a Zebra. Scrap metal. Barrel and piston might be economical option, but this piston looks like it has seized and kept going after it cooled down or something along those lines. There maybe a lot of alloy dust floating around the main bearing and seals, big ends and little end of the conrod could be contaminated too.