[Dougm]

550XUV S4 Briggs engine. Suddenly started smoking and had major power loss. Good compression and starts up fine with new plugs installed. Spark looks weak at first then stronger then seems to be intermittant (both sides). Any thoughts on cause/repair?

 

[200mph]

Curious what compression values are for each cylinder and if done hot or cold.

What color smoke.

Pictures of spark plug after it has been acting up.

Intermittent spark could be from damaged plug wire (corrosion, pinholes in insulation, broken wire, etc)

 

[Dougm]

As I remember, compression values were @145 each side. Test was done on a cold engine, I did not give it much warmup running time. Smoke is white. Do not have plug pictures, but black, carbonized (not really wet).
I do not thing plug wire damage is the issue due to both sides seeming involved and rapid onset of the problem.

 

[200mph]

With poor spark one would expect plugs to be partially wet. And performance would degrade as it is under increasing load. Greater spark energy is typically needed as load increases.

How can you tell spark is weak? O-scope?

Do you have a spark tester? Typically have an adjustable gap to see when spark no longer jumps the gap.

I’m wondering if it is a fuel quality or fuel delivery issue, but you’re the one seeing the symptoms first hand snd the fact that you have compression results tells me you have done experience working on internal combustion engines.

 

[Dougm]

I have spark testing attachments (2) that I can hook up and then start/run the engine. Power loss is most noticed going uphill (load). Fuel is non-ethonol preimum and fresh.

 

[Dougm]

Still have not resolved this problem. I have also dropped the ball for a while in favor of more pressing problems elsewhere.
Really think this could be an issue with the ignition. Is there any info about adjusting or replacing the ignition/timing parts on this Briggs & Stratton engine installed in a JD 550 Gator?
I do not even see how to access the flywheel cover.
I removed the primary clutch on the other side and it was a nightmare to access and pull!