Briggs engine repair- a tragecomedy...

[Mcbreja]

So, I know you guys will appreciate this.

My mom's lawnmower wasn't running. I, being the great son that I am, decide to fix it for her. I started with cleaning the carb, changing the oil, and putting a new spark plug in. It still wouldn't start. I hook up a spark tester and find that I'm not getting any. After a lot of cussing and a bit of research I figured out it was the stop wire. I checked that and found I wasn't getting good contact. I cleaned the wire and contact up, put together what I needed to and gave the cord a yank. Bam! It fired right up.

It still wasn't running quite right. I was getting some backfire in the exhaust. So, I started cussing again. Realizing that wasn't actually helping, I settled back into some more research. Since the last two days were well over a 100 degrees, I let it sit until it cooled off (today). To shorten this up a bit, I eventually reset the gap on the ignition armature and it ran great.

I put it all back together, got the blade on and stood there for moment basking in my own brilliance. I go to start it back up and show off my wondrous ability...

I've lost spark again.

 

[Doc Sprocket]

You may have a defective coil. Sometimes when they are on their way out, the get heat sensitive. They will induce high voltage when cool, but quit when they get hot.

 

[sexyvicta]

check throttle cable adjustment. ie make sure the kill switch thing isn't touching the throttle arm thing. I often buy 'broken' mowers to fix and thats a common problem. A very profitable problem for me haha

 

[Mcbreja]

You may have a defective coil. Sometimes when they are on their way out, the get heat sensitive. They will induce high voltage when cool, but quit when they get hot.

I just ran out to double check it since it's (the engine) cooled off now. Still nothing. I'm going to pull the blower housing back off in the morning and recheck the stop wire again. I've been thinking the coil is going out, but just haven't been able to nail it down for sure.

check throttle cable adjustment. ie make sure the kill switch thing isn't touching the throttle arm thing. I often buy 'broken' mowers to fix and thats a common problem. A very profitable problem for me haha

I checked all that. It's either the coil or that one little 6 inch length of wire.

 

[Doc Sprocket]

While you're looking over the wire, make sure the insulation is perfect and the wire is not abrading against an metal surfaces.

 

[Mcbreja]

While you're looking over the wire, make sure the insulation is perfect and the wire is not abrading against an metal surfaces.

Done and done.:biggrin5:

 

[Doc Sprocket]

Waitaminnit!!! You said something about the kill wire "not getting good contact". The kill circuit needs to be OPEN for the engine to run (ie: NO contact)!

TEST- Completely disconnect and remove the kill wire and try to run the engine. If it works, it's shorting out somewhere. If the engine still doesn't fire, then the problem is elsewhere.

EDIT- Maybe the kill switch (actuated by the bail handle) is failing.

 

[sexyvicta]

oh yeh does this thing have one of those flywheel break things? look at that aswel

 

[Doc Sprocket]

If it was built in North America in the past several years, it must- and that same mechanism must be tied into the kill switch. Come to think of it- how old is this mower?

 

[sexyvicta]

^yeh we don't have those down here. have come accross a couple though

 

[Doc Sprocket]

Less safety features where you're at, eh? I guess you can be trusted not to mow over yourselves, whereas we cannot. LOL.

 

[Mcbreja]

I don't know the exact age of the mower, but I'm guessing around 4 years old. The kill switch is actuated by by the bail handle. My apologies for not making that clear earlier.

Disconnecting the wire was the test I was going to run in the morning. I didn't think about the possibility of the switch being the problem. I should've started this thread earlier. I'll get some pics up in the morning to make everything a bit more clear.

Edit- I got a resistance reading of 5.09 on my multimeter (20K setting) off of the plug wire if that helps with anything.

 

[sexyvicta]

unplug the wire that conects to the flywheel break and check for spark again.

Less safety features where you're at, eh? I guess you can be trusted not to mow over yourselves, whereas we cannot. LOL.

yeh no emmisions laws on mowers etc either haha. So we get fancy/3rd world "not for sale in north america" engines and twostrokes

 

[Doc Sprocket]

Dang- You still get 2-cycle equipment? Jeez... Lucky buggers!

 

[Mcbreja]

I disconnected the stop wire and got spark, so I'm pretty sure that's my problem, but here are some pics.

Alright, here is a pic of the engine to give you the general idea.


This is what the stop wire hooks into from the coil.






The suspect wire. There are no abrasions or anywhere for the wire to make contact with the engine to short it out.



For absolutely no good reason, a cat in a chicken suit.

 

[Doc Sprocket]

Ahh. There's your problem. Poor cat has an identity crisis...

LOL- Okay- so the problem lies in either the wire or the switch. Mmm- check the stroke of the bail mechanism (cable?) so see if an improper adjustment may be causing the switch contacts to be closed or very near closed in the "run" position.

 

[Mcbreja]

Ha! I was just checking that that. As far as I can tell, it never loses contact with the mechanism. I think I might try a piece of electrical tape to act as an insulator.

 

[Doc Sprocket]

Have you got a continuity tester? (Or even a multimeter with a resistance setting)? With the wire OFF the switch, check continuity from the terminal to ground throughout the range of bail travel. You should have no continuity with the handle in the "run" position, and as you start to release the handle, the circuit closes. Leave some free play so that you can release the handle maybe 1 inch before the switch closes.

 

[Mcbreja]

Yes sir I do! I'll go try that now.

 

[Mcbreja]

So I checked it with the multimeter and was getting wildly varying readings. That's when I realized the kill switch was moving under my fingers while I was repositioning trying to get the meter to behave.

I got an index card and made some "spacers" to hold it still.



They wound up working and the engine is alive again.

I expect they won't last too long, but I was planning to to tear into the engine and give it a good servicing this winter anyways so hopefully they'll get me there.

Thanks for the help guys!