DGS 6500 Motor Will Not Start

Usual cause is overheating
The valve guide shifts so the valve spring becomes coil bound before the pushrod has finished pushing
Other cause is the valve hitting the piston
Inlet & exhaust cam , pushrod & valves are the same lengths so should sit exactly in the same position when unloaded
 
I'll pull the head tomorrow and take a look. Then I guess I am shopping for a head gasket, as well as push rods.
 
More like you need a new head too.

Now you would need to look-up the with both its model number (drop the ending "S") and spec number. "S" just indicates it has an electric starter. Something like SV735 - ##### without the spaces on either side if the dash. Sometimes when using Kohler dealer site we just go by the spec number.
 
Why a new head? What issues should I be looking for?

I pulled the head and looked inside. I see no signs of contact between valves and piston, cylinder walls look okay, nothing except a little oil in the bottom of the cylinder. I cleaned up the piston using a little Brakleen and will get to the head once the day cools to anything under 100F.

Photos are attached.

I was given this mower a few years ago. I forget why the previous owner quit using it, but when I got it it needed tires, drive and mower belts, a couple of pulleys and a gas tank. And a battery. The engine was packed with dirt and grass and it took me a while to wash it all out. I can see a motor like this overheating with all the cooling fins clogged. After using the mower a bit the ring gear broke and I managed to find one on the Internet. Sears did not carry it.

With the damaged push rods the 90 psi compression I was getting sounds pretty good actually. Maybe once the valves can open and close I'll get better numbers.

One thing though, it seems I should have been able to get the motor run, if poorly, on one cylinder. Or at least give me a puff or two once I squirted starter fluid in it.

Mike

P.S. What is a good source for parts for this mower?
 

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The head cleaned up okay and the valves seems fine. I didn't take them out but the move okay.

I ordered a gasket set and push rods. Crossing fingers that this fixes it.

Mike
 

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Valve guide positions? What is that?

I'll check valve heights. I assume you're hinting that the valve seats wear out, like in classic Opel motors when you don't use leaded gas and the valves pound themselves into the head.
 
Apparently never did cylinder head reworks.

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These are located under the springs. They sometime move out and limit the amount the springs can compress once the springs hit their limits then push rods will bend. In these heads they are usually the same height for all the valve guides present.
 
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