lawn mower engine not starting ?

[robb]

5.5 hp Brig&Strat vertical shaft lawn mower engine not starting.

Original problem ... When starting it went straight to full throttle mode for a few seconds then died (like hitting a kill switch). I found the throttle valve was stuck in full on. I gave it a little nudge and it was working smoothly. Then i broke the pull cord trying to restart. I fixed the pull cord and re-assembled top.

New problem ... Now engine won't fire or huff or anything. If i use the gas primer bulb and pull the plug it will be a bit wet. So I checked spark on the plug. The sparks are there nice and bright although maybe a bit orange. I checked the spark with an automotive spark gap tester , it gave a bright spark out to about 3/8 " (1 cm). Air filter seems ok. Took float bowl off in case there was water and no water. I drained some gas out of tank in case there was some water there.

If i spray some starter fluid in the carburator (yes, air filter removed) I might get a small huff or fire but that is it. Occasionally i get what sounds like some backfire/cough ??? So i checked the safety/sheer pin on the flywheel to make sure it had not been wrung/spun. The pin looked looked fine ,not budged in slightest bit. The coil to magneto flywheel air gap looks nice and tight i measured 10 - 12 thousanths (.010-.012) ".

So what am i missing ? what to check or do ?

thanks for any helpful replies. robb

[Hustlin' Hank]

Sounds like your intake valve is not closing (low compression). Check the gaps. If out of spec, lap in valve and grind down to specs.

Hank

[Winston]

(...)

(...)

Sounds like a classical case of flooding. Remove sparkplug and yank starter cord several times to dry out the cylinder.

Replace sparkplug and open the throttle all the way.

Yank cord and close throttle as soon as it starts.

--Winston

[Johnl]

[Eric in North TX]

One more possibility, When it took its full throttle run it could have sheared the flywheel key & thrown the timing off. The only way to find out would be to pull the flywheel. I usually accomplish this by; loosening the nut, putting 2 screwdrivers under it and pulling up while smacking the crankshaft with a hammer, where it sticks through the flywheel. Easier with a helper, but doable using your knee to pry the one screw driver.

[DanG]

timing key. Costs about a dollar. Take the mower apart to get to it. Pull the flywheel, replace timing key, reassemble, start.

[clare]

Except he clearly states he checked it and it was OK.

[Bob F]

[Oren]

Cracked/splitting plug wire?

Stuck butter-fly baffle/choke?

[Tony]

A spark plug will spark easier outside the engine. Under compression it takes more voltage to spark. In general a yellow spark is weak, a blue spark is stronger.

[Oren]

Looks can be deceptive. I've seen one shear pin that "looked fine", but after removal found a small crack (slight twist). Just a little offset on the flywheel can change the timing.

If I went so far into the flywheel I always sand paper the magnets inside, clean any corrosion, etc.

[Larry]

Cracked/splitting plug wire?

Stuck butter-fly baffle/choke?

***

When you had the starter asm off, was there an o ring or gasket between the starter asm and the block. This seal needs to be there and in good condition. I had the same problem - mine used a large o ring which I replaced and coated with gasket silicone before replacing the starter asm. Ran like a new machine then.

Larry

[robb]

Thanks to **all** for the helpful replies. I will try them as problems warrant,

I started with simplest suggestions first.

Tried the flooding clear (old spark plug) ... no joy.

Buy and install **new** spark plug. I prime and it fires up on first pull ... great ??? maybe

Sounds fine and seems to be running as smooth as before.

Try to cut some grass. Now the forking mower has a new ( bzzzzzzzit) every time i go to turn the mower. Well the blade seems to be grazing/buzzing the edge of the metal shroud bed whenever the mower bed is flexed .. as when turning or lifting up on the handle.

Well F--it. I'll just avoid those movements and go slow. On the third pass across the yard, going straight and no buzzzz, the mower justs dies .... Buhhhhhhhhhhhhh !

It won't restart and will only fire after priming it but then it justs dies again.

So went to check it out again and found the buzzzing by the blade is because the damn blade is cocked to one side about 1/2" inch but it is not clear why yet.

Looks like the engine shaft is bent ??? but that makes no sense as i have had this mower new for couple of years with no problems and i do not recall running over anything that might sheer a safety pin much less bend a shaft ???

So now i need to pull the blade bushing/holder as it is frozen to the shaft , it usually just slides off by itself in the past when removing the blade. So that may be a bad omen.

Bent vertical shaft ? is it possible ? why did it die after running so great for about 10 minutes.

robb

[Stormin Mormon]

Might be flooded. Take the spark plug out, turn the handle to off, and give start rope a couple yanks. That will air out the cylinder. Put the spark plug back in, and see if it goes.

[Van Chocstraw]

You shouldn't be allowed to have a lawn mower.

[Oren]

And some computers shouldn't have people, right?