The engine on my leaf vac wouldn't start & I diagnosed low compression. It's a 5HP B&S. Here's a picture of the exhaust valve seat (after lapping):
Does it (the seat) need to be replaced? The B&S Repair Manual says that after replacing a seat, it needs to be cut. How important is the cutting? I'm not about to buy a cutter & I'll take the engine to a repairman instead.
Well, I adjusted the valves, put it back together and tried it. The compression was much better, but it still didn't start. It fact, it had a terrible kick-back. Which was due to the flywheel key being sheared and the timing being off by 90 degrees! Which was very likely the only problem all along, even though the compression did test poorly.
The key replaced, it still doesn't start! Arrrgh! It has spark & won't start even with gas squirted in the cylinder.
Well, maybe it's the valve clearances - that's the only thing that's changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is tight). Is the clearance that important? Or is it likely something else entirely? Although I don't know what that could be.
I finally got back to this engine (life kept intruding).
Jon Elson wrote: > No, these small differences in valve clearance will not prevent it > from running.
Great, I didn't want to fool around with them any more.
It had points, then was converted to breaker less. The points are still there & the wires cut.
Maybe "kickback" wasn't the right term. 'Cause there wasn't ignition, I think. What happened was, as I was pulling the start cord, there was a very abrupt & solid stop. So much so that I hurt my rotator cuff, not seriously, though.
I just occurred to me that maybe that was what sheared the flywheel key. In fact, I just looked and it's sheared again! WTF?
Lloyd E. Sponenburgh wrote: ... > Since (DAMHIKT) the points gap can shear a key, I'd be looking at that. ...
That's a new one for me. It does have the old points there, even though they aren't used. Is it the plunger that does it? It fits, though, 'cause the key has sheared again.
Summary: 5 hp B&S engine wouldn't start. Serious kickback. Replaced broken flywheel key. Engine has breaker less ignition.
I previously reported that it was now starting. That's only partly true. It may or may not start & is hard to keep running when it does. Still has kick back.
I looked into the ignition some more. The engine originally had points but is now breaker less. I seem to recall at one time that I simply put on a breaker less ("3 legged") coil that I happened to have laying around when the original coil went bad. I'm now finding stuff on the web that indicates that you can't do that. There are conversions to keep the original coil and replace the points and there are conversions using a new flywheel and a new 3 legged coil.
I suspect that this hacked-together hybrid simply has bad timing and somehow over the years (10 or more) it has gotten by. The proper way to fix this would be to install the "Magnetron" point replacement and a
2-legged coil, or a flywheel intended for a 3-legged coil. Oh, wait ... I _have_ a 3-legged-coil flywheel on a "spares" engine. I'll try that - why not?