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I have a Craftsman 675 Series B&S push lawnmower 944.367450 model approx 5 yrs old. It seems my LM will not start unless it sitting in the sun for at least 15 minutes. It could be clouldy at 70F and it still won't turn over. After 15 minutes in the sun...boom first pull. I've tried changing the spark plug, air filter, engine oil, emptied old put in new fuel and dismantled carburator 3 times cleaning it with carb cleaner including checking/cleaning jets. Still no luck. Anyone have any suggestions?

Check that the engine safety shut off switch/cable is not binding or sticking.

Inspected Operator Presence Control Bar cable to switch. Seems to be ok.

Forgot to mention. Lawn mower has an automatic choke.

Pull the air cleaner when it is cold and check to see if the choke is closing. The thermostat device behind the muffler can stop working as well as dirt and trash buildup in the linkage under the flashy engine cover. My neighbor has two snappers that mow like mad but to start them takes a bunch of incredible hard wild pulls from him and his sons to get them going.

Wondering if it needs a carb replacement. Either that, or just cut the grass only sunny days. Seems bizarre.

Have you check out the choke to see if that working the way it should be..? when engine's are warm or hot they don't normally require choke. maybe that's why it wants to sit in the sun...( would love to be able to do that one day) :laughing: that is where I would look.

There is a briggs bulletin on cold start problems on the readystart.
You said you replaced spark plug. What gap? Should be .030"
Check thermostat for binding.
Check and make sure choke is coming on.
If not then you have to check and adjust thermostat to make sure it is adjusted correctly between the notches on the choke lever.
If all these fail then it could be a new carb required.
Have you reconnected the small choke lever spring which isnt allowing choke to go on?

Thanks Engineman and pugaltitude. I will do inspection on the choke. Yes the plug gap is at .030"

I exposed the fly wheel removing cover. Noticed thermostat was properly in place in between notches as mentioned. There didn't seem to be any issues moving choke linkage. Choke is fully opening and closing. I did not mention earlier but yes, small choke lever spring is inserted correctly.

What type of kill switch does it have, is it a microswitch, had one of them play up on a mower would start then it wouldn't gave it some WD then alright for a few days, in the end a new one was fitted.
before you take it out into the sun, and you have pulled it many time's without it starting, is the plug wet.

It's just a Briggs and Stratton z-start mower, no priming and auto choke. Has a switch stop next to the brake. Yes plug is wet after several pulls.

Then it as to be spark, its not getting any...! so look at the kill switch, bad wire from the coil or the coil itself, take off the wire from the kill switch that goes to the coil, add wire to that so you can put the lid back on so you will be able to pull start it, and you can use the long wire to put it to earth to kill the engine if and when it fire's up, and am sure it will..!.
If the plug is wet its getting fuel, you can always look at the plug (take the plug out) to see if there is a good spark, and I mean a good spark, before you do any of the above things.

I inspected the kill switch wire at both ends and removed the armature magneto. Re-inserted it using business card. Difficult to see if getting a spark. What method do you suggest with just one person. Dog might be mans best friend but not a very good assistant.

I placed the plug grounding it to the engine. Did get a spark but not on every pull. Since I can't get it to turn over is it fair to say it isn't giving a strong enough spark meaning I should replace the armature magneto (ignition coil)?

Vancouverite said:

I placed the plug grounding it to the engine. Did get a spark but not on every pull. Since I can't get it to turn over is it fair to say it isn't giving a strong enough spark meaning I should replace the armature magneto (ignition coil)?

Click to expand...

There isn't that much more you can do now apart from renewing the coil (magneto) you should be able to see a good strong spark with every pull.
Seems you have a bad coil, HT lead or kill wire, kill wire maybe going to ground somewhere.

You need a spark tester to check for spark.
You need to load the coil to its full capacity which a spark tester will do.
You also dont know whats happening to the plug when it is in the cylinder and under compression conditions!

Thanks gentlemen, I'll pick-up a tester and try it out. I'll give an update.