Lawnmower Engine Starting Tips??

[Al Skierkiewicz]

Originally Posted by mtaman02

Ok, I have an Update and a question


Do you know how a spark plug wire is constructed? (whether it has a 2 wires for + and - or just one wire)

The spark is generated by a magneto, a coil of wire that a magnet passes by while the engine is turning. One side is connected to the spark plug and the other is attached to the engine block. You could try to put a switch in the ground side of the magneto coil. Many designs do not use a wire for this so you will need to check if yours has a small wire going to a screw on the block.

[mtaman02]

Originally Posted by Al Skierkiewicz

The spark is generated by a magneto, a coil of wire that a magnet passes by while the engine is turning. One side is connected to the spark plug and the other is attached to the engine block. You could try to put a switch in the ground side of the magneto coil. Many designs do not use a wire for this so you will need to check if yours has a small wire going to a screw on the block.

I shall check, thanks for the tips and as always i will keep you guys posted =)


**** UPDATE ****
Well I did find that wire going to the engine block and used a "Cheap" Switch to see if it would work and it did, the only problem was that the switch broke - darn antique garbage =) oh well I'll go buy a better constructed switch tomorrow and make sure its a permanent fix.

[Evan Austin]

Most, if not all of the old, smaller Briggs engines used a diaphragm which acted as sort of a fuel pump, on vertical crankshaft engines it was between the carburetor and gas tank, on horizontal crank engines it was under a plate on the side of the carburetor. Briggs still uses diaphragms on some vertical crank engines which are usually on cheaper mowers. Most newer engines don't even have such a thing. If it has been sitting as long as you say, I would replace it. I would also remove the carb from the tank and spray carb cleaner in every passage I could find, the blow out with compressed air. Also, if your carb is metal, make sure the mating surface to the tank is flat, this area warps very easily.
As another note, on engines that act as yours does, I would try removing the air filter assembly and choking the engine by putting your hand over the air inlet (leave the actual choke off). If the engine dies out, try choking it some more and see if it comes back.
By the way, to see how old your engine is, look at the serial #. On a Briggs, the first 2 numbers are the last 2 numbers of the year of manufacture, the next 2 numbers are the month, the next 2 are the day, the last 2 are the production line the engine was built on. On a Tecumseh, the first number is the last number of the year, you don't get to know the decade. On a Kohler, you take the first 2 numbers of the serial # and add 70 to get the year.

[sanddrag]

Originally Posted by Evan Austin

As another note, on engines that act as yours does, I would try removing the air filter assembly and choking the engine by putting your hand over the air inlet (leave the actual choke off). If the engine dies out, try choking it some more and see if it comes back.

I tried that and it made the engine start and continue to run (although not very strong/fast). So what does this mean? It will not run under full choke on the carb but if I keep my hand tight against where the air cleaner usually goes, it will run. What does this mean?

Also, I found the plate on the side of the carb, but I haven't taken the carb off again to open that and inspect it.

[Mike Martus]

EAsy - Bad headgasket like I said earlier.

[sanddrag]

I don't have a torque wrench (should probably get one) but to me the bolts seemed a little loose (especially the two by the exhaust) so I tried tightening them up a bit but it didn't do anything.

I haven't been able to spend much time on this thing lately because it is only cool enough to work outside before 7 in the morning or after 8 in the evening. I still have to pull the carb off again and see if there is anything wrong (like the ball-check valve you mentioned) in the little yellow plastic fuel tubes.

Maybe one of these days the weather will be cooler and it will give me break so I can work on it. I would take it to the service center but since they are the only one around here they said they are 10 weeks out ( ) on doing any repairs or service for anyone (I guess partly because they service chain saws for the forest service so they are probably very busy).

So, maybe one day I can tear into this thing myself. They aren't especially complicated are they? Where do you start (or what are the basic steps) and what do I need to look out for in the disassembly process? Also, what should I be looking for that might be a sign of the trouble (besides the head gasket)?

Last, I noticed that the top of the piston is very black and oily and nasty looking. Does that indicate anything?

Once again, thanks to everyone for the help!

[downhillpat241]

Originally Posted by Mike Martus

EAsy - Bad headgasket like I said earlier.

One easy way to tell that. Snag a can of ether and blow a little around the cyl. head. See if it speeds up. try not to spray the muffler or the plug. And don't be a bad larry (love that word) and pull the plug wire, number 1, it's old and sparks tend to leak ot that rubber boot. Number 2 the resutl ain't gonna be too pleasant....radio shack's momentary push button switches work awfully well for that and they're cheap. If it still has a carb problem, let me know, I'm the master....

pull the mixture screw out of the carb, check the little rubber gasket.


If you ask me briggs' Vacu-jet and pulsa-jet and pulsa-prime carbs are the worst designed pieces of plastic junk that I have ever seen. Did I mention I hate them? The day that briggs starts using Mikuni Roundslide carbs is the day when all is right with the world.

And should you need parts let me know my shed looks like sanford and son organized and on steroids.

[downhillpat241]

Ooooh blackness.... you're flooding it and your rings might be gone. Or it's probably just 20 years of carbon build up. Get a putty knife and scrape it off, use sand paper too but don't damage the mating surfaces. Get a can of PB Blaster and use that while cleaning it. Smells like moth balls and diesel but worth it's weight in gold.
Look down the cylinder wall if there are deep marks, don't even bother. If there are deep marks just forget it Essentially it's the second most easiest engine to fiddle with.





Let me know and send some pics along of this bad larry. If you want to get deep into it I'll give ya a hand.....from waaayyyy ovah heah!!

[mtaman02]

Well final update


I have now attached a switch that i bought from autozone and lemme tell you this 20 yr old mower purrs like a kitten and turns off perfectly when i turn the switch on =) thanks for all tips guys