lawnmower problem - Part II

[ProdigySBC_SUX]

I had replaced the coil and gotten spark back to the plug but it still wasn't starting. While the plug looked good, I still went and bought another. The 'old' plug was indeed one of the flavors that has the resistor to cut down EMI.

When I put the new plug in it started. However, it ran rough and very finicky. When I started using it it would stall very easily. I got about

30 minutes useage out of it and had to start it about 15 times. Each time it got progressively worse and finally it wouldn't start at all.

As I was putting it away, I noticed there was some oil dripping onto the deck that appeared to be coming from somewhere around where the carburetor attached to the engine. (I am very sketchy on this as I was in a rush and haven't gone back and looked more closely.) I had not had the lawnmower tilted or flipped that day.

[I still need to check the flywheel key as sugested by Stormin Mormon.] [Q: If running the oil/gas mixture in the 4-cycle fouled my valves, could pulling the plug and filling the cylinder or spraying lots of carb cleaner in the plug hole (while ocasionally rotating engine shaft to insure the valves were open sometimes) at least partially clean the valves?]

On a related note and a different thread, I bought a lawnmower from somebody else here that was sold as 'not running'. I only paid $10 for it and was hoping that maybe between the two I could put one together and have a running mower. It however sounds real sick when I crank it and was probably $10 wasted....

[Doug Miller]

[...]

Do this first, before you spend time checking other things.

You need to do it anyway... and I suspect that you will find that's the problem.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

[Stormin Mormon]

More counsell.... part two.

[Mark]

check that the air intake filter is not clogged with oil.

been there done that

mark

[ProdigySBC_SUX]

So I Tore into the engine looking for this pin somewhere on the shaft and yea verily, I think I found it. There is a groove axially cut into the crank shaft (? axle?) of this engine and the coil/timing flywheel appears to be mashed down on this shaft. The flywheel also has a groove cut into it to accommodate part of this square metal pin.

The flywheel appears to have been 'wrenched' a bit and attempted to shear that pin. Hence to two grooves of the flywheel and the grankshaft are not exactly aligned and are off about 1/4 - 1/5 of the width of that groove - easily somewhere between 5-10 degrees I imagine. Soooooo it looks like I need to borrow a pulley-puller and pull that flywheel to get at that pin to replace it.

From what i have picked up about that pin, however, I am a bit confused. I thought I had learned somewhere that the purpose of that pin was to allow the engine crank to be able to (at least partially) disengage from the axle of the blade in case the blade hit something very substantial and whose sudden change in rotation could damage the internals of the engine. Maybe this pin goes farther in/along the shaft and does something I am unaware of but right now, the ignition flywheel appears to be out of alignment and that could be a big problem.

I did see where the oil that I thought I had seen leaking was indeed spilt. I'll keep my eye on that...

The air filter was something I had started with and indeed found it to be pretty skanked so that was changed out very early on in the game.

=====

RE that second mower.... bboooooooo. That appears to have been a 'pig in a poke'. When you pull on the rope to try and start the mower there is an awfull metallic banging noise that appears to come from the engine. I have looked underneath to be sure the blade wasn't hitting anything and 'unfortunately' it wasn't.

So, out of curiosity, are these motors 'mostly' interchangeable from mower body to mower body? i.e., have the mfgrs standardzed on mounting hole patterns, crankshaft depth/length, etc.? Surely not...

Anybody here have a *favorite* book for small engine repair? I was looking at several on Amazon...

Regards,

PSBCSux

[Terry]

The blade is mounted on a hub on the bottom end of the engine crankshaft and it has it a similar 'key' which engage the shaft, in order to turn the blade. I've broken that and in fact the hub which seemed to made of some 'white metal' on one occasion by hitting a rock. I understand that is, hopefully, supposed to protect the guts of the engine. I've never broke an engine.

But up on top it certainly sounds as though the ignition timing flywheel is mounted way off and therefore won't run!

Also sounds like you may be able to salvage or even fix both machines.

The ignition flywheel has a magnet/s in it which induces a current in the coil as it spins around to make the spark for the plug. It has to be in the correct alignment or the spark timing is wrong! Also there must be slight clearance between the face of the coil and the magnets (very carefully sand off any rust) cos lack of clearance may 'short out' the magnetic path and cause a poor, or no spark. The magnetic strength of the magnet imbedded in the inner face of the rotor should be OK.

But hey brand new, at Wal Mart, here 3.5 HP Briggs and Stratton mowers are $149 Canadian (roughly $120 US dollars!). Plus local sales tax! And that's not even 'On sale'.

We are on our third mower in some 50 years; this now 8 to 10 years old one being the first 'new' one we ever bought. It was preceded by a series of used machines, coddled together from various bits and pieces of bases and engines. I gave the remains of the old ones to our local small engine repair guru. 'Fred Hammond'.

Fred can use any of the parts to fix machines cheaply for other people; his costs always being so reasonable that we usually give him a 'few extra dollars' cos he's practical, knowledgeable and helpful. You may have a local Fred Hammond if you ask around?

Terry.

[Rich]

That is indeed the purpose of the shear pin but it also is critical in timing. Even being "'wrenched' a bit" will disturb the timing. The flywheel must be pulled and a new pin inserted. You most likely will need a puller to get the head off.

scroll down to Timing section:

There are most likey two holes on the flywheel for the puller.

Yeah. Engines are available.

Northern Tool has a wide selection of new ones:

[ProdigySBC_SUX]

First off - thanks to all who posted with help.

My last issue with this mower was indeed the partially sheared pin between the magneto flywheel (?) and the crankshaft. I replaced it and primed the bulb three times and it started on the first pull. Ran great and got my lawn mowed - finally after about 2 months. Sure glad it was winter and the grass was slow.

The engine did not 'leak' out any more oil.

After I fix some other issues around here I'll look into the other mower I picked up. I ordered a book on repairing mowers and small engines but it hasn't gotten here yet. Maybe some night I'll put it on the flatbed and scan it in for everybody...

Thanks.