DGS 6500 Motor Will Not Start

[m610]

It was running fine last night then acted like it ran out of gas and quit. It probably did so today I added gas and it will not start. I checked:

Fuel - I can see it at the fuel filter.
Spark - I have a handy tool that lets me see if the cylinders are getting spark. Both are. I cleaned the spark plugs anyway.
Air - I'm pretty sure I have plenty of air, but to be sure I removed the filter.
Compression - 120 psi on the right, and a not great 90 on the left. But, it is and old tractor and neither are at zero.

It cranks strong but never fires, not even a puff, even when using starter fluid.

Possibly timing? I have no idea how that is set or checked.

Any ideas?

Thanks, Mike

 

[StarTech]

That series came with a Kohler or Briggs engine and we need the engine model and spec numbers. But current I thinking you have a valve related issue.

 

[m610]

Thank you for your reply.

The engine model is a Kohler SV735S.

I found manuals for it. It says compression should be 160 psi, so I am a bit low or did not test under the same conditions. Still, low compression alone shouldn't keep the engine from starting.

 

[bertsmobile1]

Get a pair of new spark plugs
put a SHORT shot of starter fluid down both plug hole & crank the engine
It should fire at least once
If it backfires through the carb or exhaust that suggest a valve problem
If it does not fire at all that suggest an ignition timing problem
You might need to do it a couple of times to get a definative answer
Get back & let us know what happens

 

[m610]

I just did those things. New plugs, correctly gapped, starter fluid in the cylinder, fresh battery, and the engine cranked strong but never even puffed. I pulled a plug and confirmed it was firing, and with a nice blue spark, too.

I'm not a mechanic but I know my way around engines (classic Opels), and this makes no sense. Even if mis-timed I would expect something, even a backfire.

Mike

 

[StarTech]

Not if the intake valves are not opening to allow in fresh air. Fuel can't ignite without oxygen. Or if the ignition is off quite a bit. Pull the rocker covers and check the rockers movement as you may dropped a push rod or two.

 

[m610]

Will do. Give me a half hour.

 

[m610]

Welp, the right side cylinder looks okay, but the left?

I suspect more than a little mis-adjustment is the problem here.

Right:

Left:

 

[m610]

Push rods are bent. The question now it, what was the root cause, and how bad is the damage?

I was given this mower a few years ago. I wonder if I've been running on one cylinder this whole time. Motor ran smooth, but...

 

[m610]

The rocker arms on the right side move like they should when I crank the engine.