dead B+S mower engine

If you do pull the flywheel, shine the magnets (two) with some emory cloth. Clean any contacts and shine them.

I've seen surface rust (humid areas) on the flywheel magnets - enough to diminish the good clean firing of the ignition.

Something I've noticed on engines like yours is the need for valve clearance adjustment after the engine has rub for a number of years. I've worked on a lot of standby generators and the overhead valve engines are easy to adjust the valves on. The valve in head engines such as the one I believe you have is a different story. I had one that would only run if I preheated it with a propane torch which caused the metal to expand enough to let the valves seal. Here is a video that explains a lot about dong a valve job on a L head engine.

Check your local lawn mower "bone yard" for a carb that hasn't got the bushings all worn out of it and start over with it.

NOT EMERY CLOTH. Some of the emery is magnetic. Use Alox paper (Aluminum Oxide)

Now, that sounds like the voice of experience. I knew a kid one time who ran an ungoverned lawn mower to get to town and back. A couple times, until it over revved, and broke.

We recently had a thread about getting home on paint thinner, when the gas tank was near empty. I've heard gas engines run well on a spray of WD-40.

Yes, better to kill a few things before they hire on with you.

Easy off oven cleaner is excellent for cleaning carbs. Strips off gum and varnish. Rinse well, and dry before reassembling. Best carb cleaner I've ever used.

Champion had a run of bad CJ-8 for a few years. That's a brand I avoid.

During start, the throttle is wide open, and the choke closed.

The mowers I've serviced. if the valve clearance is too low, the mower runs 15 minutes, fades out, and died. Restarts after it's cold. I learned that in a small engine repair course. One guy a couple streets over was going nuts on a mower repair, and turned out valve clearance was the problem.

If compression is to low it wont start easily or at all, you need a

Because the propellant is basically Propane - which gets the kerosene lit. Bulg WD40 won't light worth crap.

Just don't forget to rinse promptly. - and thoroughly. On a zinc carb it's not as bad as on aluminum.

Didn't know that about the propellant. I've never tried bulg WD40.

Yes, promptly is good. Within seconds of spraying the oven cleaner. metals damage due to the strong alkalai, is a very real possibility.

Yes - watch this space... I brought home an almost-identical mower yesterday, except that it's got the 7-speed transmission and an 11HP B+S engine (rather than my 5-speed / 10HP). I think the carb's identical though - I suspect most of the engine is, and it's just a different bore/ stroke.

Actually, the 'new' mower's possibly a better long-term candidate than the current one. For 15 years of standing out in the open it's pretty solid. Front axle and tires are shot, and there's something up with the deck, but those would swap over easily enough.

I think I'll use engine parts from it to get my current one going (I can last about one more week before mowing), but after that screw around with it some and see if I can get it up and running.

cheers

Jules

Yep - I was just ruling out a governor problem by manually holding the throttle (just in case the governor was screwed and trying to throttle things way back before the engine had chance to cough into life)

I'm wondering about the compression, now. Can low compression result in an engine that won't even start/run under no load?

It's got some compression for sure (nice healthy hiss from the crankcase breather on the down-stroke if I turn by hand), but I tore into the 11HP engine from the donor mower I picked up at the weekend, and that engine's piston fits *far* more snugly in the bore than on the 10HP. It slides well (so no apparent issue with ears of it sitting there unusued), but fits better with no detectable side-to-side movement if I try wobbling it, unlike the 10HP.

(Although if it is a compression issue, I still don't get why it was running last season and magically broke over the winter...)

Oh, I cleaned up the carb on the 11HP and tried it on the 10HP. It will fire consistantly for maybe 4-5revs, then die, so not really any better than the 10HP's own carb was. No different swapping the plug, either. Magneto is unfortunately trashed on the 11HP, so I can't try swapping that.

cheers

Jules

Jules Richardson wrote: ...

Certainly, but it has to be pretty doggone low to not run at all...

If you can use a thumb in the spark plug hole and keep it from blowing by, it's a good chance it is that bad...

--

First.......put in a new plug. Just because it fires, doesn't mean the plug is good. I have seen engines run (poorly) with a bad plug.

You say it has compression, but does it have enough. Just because the valve seats look good, doesn't mean the are closing all the way. Check the gap, should be approx. .04

Hank