Here's the ID label data, as best I can make it out:
FAMILY 2002 US I: PA PH 2
2PWES.0424CS
DISP. 42CC: EM
SERIAL # 02288D200830-3: (06-59)
Durability Period 50 hours
The small engines place that I frequent gave it to me. They'd have given it to a trade school, but I guess the school didn't want it, so I got it.
There's fuel in it but it won't start. I'd really like to have this machine in useable condition. It's all the chainsaw I'd ever need. Let's see what's what with the thing.
Top Cover Removal
Three obvious screws, T25 Torx recess.
Spark Plug
It's an immaculate Champion RCJ7Y. It looks like someone replaced the plug, couldn't get the engine to run and gave up on it.
Hex is 3/4" A/F (across flats). Gap is a tight 0.030". I've been cranking the engine, and the tip of the plug is bone dry. That doesn't bode well for fuel system fitness. Let's at least see if we have spark.
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And we have spark.
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Fresh Fuel
First thing to try is fresh 40:1 fuel.
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And that's no go, so it's on with investigating the fuel system.
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Left Side Cover With Recoil Starter -- SATURDAY, MAY 25, 2019
The left side cover has to come off for access to the primer bulb. There are four obvious screws, T25 Torx recess.
Note the following regarding the primer bulb:
- The bulb has two nipples -- a longer one in front and a shorter one in back.
- The longer front nipple is fuel return to the tank.
- The shorter rear nipple is fuel draw from the left side of the carburetor.
- Two No. 6 x 5/8" pan head screws, No. 2 Phillips recess, fasten the primer bulb to the frame.
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Carburetor Removal
Underneath the foam air filter element there are two washerface hex nuts, 8mm A/F. Remove those nuts and you're presented with a diabolical arrangement. The process of extracting the carburetor defies tidy exposition, so I won't even try.
Anyway, the carburetor is a Walbro 236 WT391, as best I can make out the embossed characters. I deleted the mixture screw limiting caps, and tore down the carburetor. The metering diaphragm looks marginal, but it should work well enough to get something out of the machine. I found nothing else untoward. 'Reassembled the carb and the saw, and it's no go. I've not been able to get so much as a single 'pop' out of the engine. Whatever is wrong is a mystery to me, and I don't think a new metering diaphragm will solve it. The saw can go down to the bottom of the yard to languish until I either scrap it, or come up with a solution.
You win some; you lose some. Two-strokes can be mystifying.
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Further Notes -- THURSDAY, MAY 30, 2019
An interesting feature is the pressurized fuel tank. There is no fuel tank vent for air to enter through to take up the space left by spent fuel; the filler cap seals tightly and perfectly. It behooves one to depressurize the fuel tank by cracking open the filler cap prior to disconnecting the fuel take-up line from the carburetor; else there'll be a considerable spout of fuel out of the disconnected fuel take-up line until fuel tank pressure subsides.
I've had the flywheel off to check that the flywheel is correctly keyed to the crankshaft. It is, so the engine can't possibly be mistimed, presumably. Can it be possible for an ignition coil to fail in such a way that it still produces spark, but at the wrong time? I don't know. It seems highly unlikely.
I've tried leaning the mixture screws, and richening the mixture screws. Nothing changes.
I've tried squirting oil into the cylinder to up the compression. That produces a brief, marked increase in compression, but the engine still won't start.
I went to Canadian Tire and got a can of their Quick Start starter fluid spray. 'Tried that. No effect.
Removing the muffler to examine the piston reveals appreciable scoring of the piston. I've been told that that's an indication of 'game over' for a two-stroke engine. Measured compression is about 60 psi, which is low, but I would expect the engine to still be able to run with that, albeit poorly. I'm baffled.
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Update -- WEDNESDAY, JUNE 5, 2019
Going on the theory that possibly something may be amiss with the ignition coil's spark timing, I ground down the flywheel's integral 'key' so I could experiment with timing.
I know, that was a gross, possibly retarded (no pun intended) thing to do, but I had nothing to lose. Needless to say, that got me nowhere. I'll just have to put the failure down to that scoring I can see on the piston, and finally give up. The saw can go in the next load of stuff bound for the scrapyard.
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