A friend has a two-cycle Ryobi RY38BP leaf blower that has stopped working. Initially I thought the whole problem was that the pull cord was messed up, as it was partially hanging out of the motor housing. After pulling on the cord several times at their house, it decided to not retract at all and the engine no longer spun. Easy fix, or so I thought. This photo is off the net.
I took the thing home and after pulling off the main shroud, I got the pull cord fixed. I put things back together and the engine still didn't start. I pulled off the shroud again (a second of many, many times on and off), pulled the spark plug and used a drill motor to spin the engine over. There was no spark. Time to order a new coil. Oh, excuse me, an "ignition module"....
The new coil came but still the engine wouldn't start, but now there was a new issue. The generic term is "kickback", and it happens when the spark occurs too early in the compression cycle and the explosion pushes the piston backwards down into the cylinder and the pull cord is yanked out of the person's hand. This next photo is of the new coil installed. It's the black plastic thing with the red wire going to it.
One thing I need to mention here is that there are no points or electronic ignition (unless it is contained in the original tiny coil), so the spark occurs when the magnets pass the coil. I checked the position of the piston at that point and it was partially on its way up on the compression stroke. That's about 90 degrees of advance, which makes no sense to me but it is what it is and the leaf blower did run at one time. Usual advance is somewhere around 5 to 15 degrees.
At this point I did some internet searching, as I figured many folks would have a similar problem with their leaf blower. Nope. The closest I came to finding something similar was a Youtube video of a chainsaw tech that had a kickback problem. They ended up changing the carburetor, which really should not be a contributing factor to kickback. But with nothing else to go on, I pulled the carburetor apart. Nothing seemed wrong so I went ahead and ordered a carburetor. Now I'm the first person to acknowledge the ready and cheap access to Chinese/Indian/Pakistan parts, and they are generally of fair quality. The coil and carb I ordered were each about $17 delivered.
The new carb came and I installed it. Still the same kickback issue. Not knowing what else to do, I disassembled the entire engine, hoping to find something broken. The first little hiccup was that the cylinder fasteners were down long holes, so I had to turn down the outside diameter of the Torx bit I was using. After turning it down, I found that the bolts were a different size, so I had to turn down a second Torx bit.
After inspecting things, even comparing to photos online, nothing looked out of the ordinary. Below photo shows the engine is back together. I put the original carburetor back on because it fit just a little better than the Amazon one.
I chose a spot to put the slot somewhat arbitrarily, so I was very skeptical that it would work. You can see in the photo below that the slot is quite a ways off from the original slot. My slot is the one on the right and it's nearly 90 degrees off from the original.
Wonder of wonders, the engine actually started and ran fairly well, although it wouldn't stay running with the choke all the way off. I put on the new carburetor and it solved that problem.
I tested out the blower on my driveway and it worked fine for the 15 minutes I used it. I really have no idea how the engine ran originally, but it obviously did run with the original coil for several years. The only thing that makes any sense to me is that the original coil had some sort of ignition timing delay (but 90 degrees?). I guess I'll never know, as I have no plans on buying a genuine Ryobi replacement coil.
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