dead B+S mower engine

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On Apr 30, 1:09pm, Jules Richardson

Yeah, I've got an old Alis Chalmers Rotary Tiller that I am debating on whether to fix or not. I had not used it in a couple of decades and my nephew took it a few years ago to try to get it going. When I got it back, it is missing the gas tank and air cleaner and I am thinking I just might as well replace the carburetor. I checked on line and the gas tank is about $70, the air cleaner is about $35 and the carb would be around $130.
That's about a third of the cost of a new one but If I get this thing going and take better care of it and use it more, I bet it would last me for as long as I am able to use it.
David
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Jules Richardson wrote:

When I was a kid, I discovered that a lawnmower engine would run on Liquid Wrench. Of course there are carb cleaners that a motor will run on while cleaning things. I've had luck with spray cleaners that have the extension tube using it to blow open the tiny ports in the carb.
TDD
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On Fri, 30 Apr 2010 09:30:21 -0500, The Daring Dufas wrote:

When I was a young lad I found out a horizontal shaft Kohler engine would run on propane from the unlit nozzle of a propane torch held in the carb venturi. Also found out the motor could easily over-rev and bust the connecting rod if you fed it too much propane. :)
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Jeff The Drunk wrote:

Someone comes to me for a job and tells me they have a lot of experience. I ask them: "How much equipment have you burned up?" If they answer none, I tell them: "You obviously have no experience, I need someone who has already burned up thousands of dollars in equipment because I can't afford it. A learning experience can be very expensive."
TDD
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Yes, better to kill a few things before they hire on with you.
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Christopher A. Young
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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.
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On Fri, 30 Apr 2010 22:09:53 -0400, "Stormin Mormon"

Because the propellant is basically Propane - which gets the kerosene lit. Bulg WD40 won't light worth crap.
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Didn't know that about the propellant. I've never tried bulg WD40.
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On Apr 30, 8:19am, Jules Richardson

It runs just not under load right, ive had several 4 motors like that and it was electrical. One a bad wire, two the ignition module, one the coil. A motors spark at idle needs not be strong to run, but to ignite alot of gas for load it needs to be strong. That doesnt rule out low compression or a carburator-fuel issue but since it runs it could be electrical. Is the spark small and weak and maybe red in color, but ive had small blue sparks not enought to go past idle. Sears sells a 4$ induction tester you just touch the wire while its running, if the spark is what dies as you load it you should be able to see it, and squirting gas in the carb with throttle open should help rule out or confirm a fuel issue. Why did you pull the head?
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On Fri, 30 Apr 2010 10:27:53 -0700, ransley wrote:

No, not running at all. I've had it run maybe a couple of revs under its own power a few times, then it dies on me (it doesn't seem consistent though - if it fires like that, I can leave the throttle in exactly the same spot and come back to it a few minutes later, and it won't fire at all)

Just to take a look at the valve seats & cylinder bore - only takes a couple of minutes, and I wanted to make sure the valves looked like they were seating properly and the bore wasn't trashed for whatever reason. All appeared OK, though.
cheers
Jules
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On Apr 30, 4:38pm, Jules Richardson

If compression is to low it wont start easily or at all, you need a 15$ tester to find out the real pressure. Leaking fuel to me means flooding, is plug wet after you try.
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Jules Richardson wrote:

Buy a NEW spark plug before you do anything else.
Jon
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On Fri, 30 Apr 2010 11:06:16 -0700, "Jon Danniken"
Also check the gap before install. Those plugs gapped at the factory are not always accurate... Get the correct heat range for the plug as they are not all the same :)
OP - loosen the gas cap a turn or two. If the cap vent is clogged the tank will create a vacuum, affecting fuel flow. Clean vent with a paper clip.
You have plenty of oil in the engine, right. If the motor has a low oil kill switch that would shut the down engine.
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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.
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On Fri, 30 Apr 2010 22:14:44 -0400, Stormin Mormon wrote:

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)
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[snip]
Is there a fuel shut-off solenoid inside the carb?
It sounds like you are getting fuel to the carb, just not through the carb.
Sticky float plunger, clogged passages, or partially functioning fuel solenoid are the usual culprits.
B&S engines have fixed timing.
A partially shorn shaft key might goof up the timing a bit, but the engine should still run if it fires at all. It's an all or nothing kind of thing.
Concentrate on the carb.
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On Fri, 30 Apr 2010 15:22:03 -0500, The Black Knight wrote:

No... I'm not sure who made the carb, unless B+S rolled their own. It's a pretty simple beast really.

Well, *something* is getting through because I can pull the carb off and it's wet on the 'engine side' of the carb body. I wonder that's actually a sign of the problem, though, and it's just not atomizing the fuel properly and is getting neat gas pouring into the cylinder rather than a nice mist (the presence of just enough vapor might explain the way it tries to cough into life once sometimes, then promptly dies).
OTOH, maybe I'm clutching at straws ;-)
Oh, other possible symptom: the carb's getting a *lot* of gas; it drips quite a lot from the intake side if I have the air filter assembly off (the bolt that holds the filter on runs right through the carb body on the intake). It's possible it's always been like that, and that's normal behavior, but it surprised me there'd be that much gas "upstream" of the choke plate.

Possible, I suppose. I checked that the float isn't holed, and the metering needle there looks good and seems to seat well (the carb sits slightly lower than the tank, so if there were a float problem I think I'd get gas pouring out everywhere even with the mower just sitting).

I can't completely rule that out, as there are a couple of passages I can't really get to (access sealed at the factory), although I can blow through them, so I know they're not completely blocked.

I might try to pull the flywheel (which times the ignition) just to check that - it'd be a heck of a coinicidence if it just happened right at shut- down last season, but stranger things have happened :-) I've certainly had keys shear on smaller engines before.

Yeah, I just pulled it again and double-checked what I could. I ended up dumping a little neat brake cleaner into the inlet "upstream" of the float and throttle, and the engine actually turned about four revs under its own power before dying (it'd only do about 1 or 2 revs by itself on gas). I can't decide if that's indicative of anything meaningful or not :-)
cheers
Jules
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On Fri, 30 Apr 2010 21:26:48 +0000 (UTC), Jules Richardson

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

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.

http://www.youtube.com/watch?v=2yr5a69TxNI

TDD
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