I am having trouble finding the reason for low compression ( and no start) on a friend's push mower. It has not been used much. He checks and changes his oil and air filter regularly. A compression check revealed 40 psi with the choke off. There is cold valve lash of .006 intake and .008 exhaust. The spark is hot and it cannot be coaxed to run even momentarily with starting fluid squirted in the cylinder. Any ideas ? Thanks in advance
Engine Low Compression on GCV 160
- Thread starter rlj
- Start date
The classic test for ring sealing is compression test BEFORE and after oil squirt. Valve lash will not show a burnt exh valve. Are the valves moving? Open the choke and throttle butterflies when taking compression. I guess broken rings or cracked piston are possible due to a latent quality or factory assembly problem. Hope some of this helps
The compression release on the overhead cam may be binding up. This can be seen if you remove the valve cover. You should have a spare valve cover because it usually gets bent up from removal.
At this time I would check the valve clearance.
At this time I would check the valve clearance.
Dear Men,
Thanks to all who replied. The problem is now resolved. I was hoping a complete teardown would not be needed. It turned out that the engine owner ran the engine low on oil at some point. Both the piston and cylinder were scuffed, and metal fragments were jammed in the piston grooves, preventing the rings from expanding outwardly.
Honing the cylinder lightly and filing the high spots on the piston was a less than ideal, yet low buck solution. I installed new rings ( $21) and put 'er back together. It started on the first pull. A compression check revealed 90 plus psi. I cut the back yard and the mower ran well. No oil burning was evident, but I'll keep a close watch on that. Thanks for your forum advice.
Thanks to all who replied. The problem is now resolved. I was hoping a complete teardown would not be needed. It turned out that the engine owner ran the engine low on oil at some point. Both the piston and cylinder were scuffed, and metal fragments were jammed in the piston grooves, preventing the rings from expanding outwardly.
Honing the cylinder lightly and filing the high spots on the piston was a less than ideal, yet low buck solution. I installed new rings ( $21) and put 'er back together. It started on the first pull. A compression check revealed 90 plus psi. I cut the back yard and the mower ran well. No oil burning was evident, but I'll keep a close watch on that. Thanks for your forum advice.
reynoldston
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If you have that amount of clearance, your valves are not closing all the way. As your exhaust valve is bigger, I am guessing that you have a piece of carbon jammed on it. This engine requires you to take the engine completely apart to get the valves out. If you need step by step instructions, email me at dvata@yahoo.com and I will walk you through, how to do a valve job on one of these engines. You will need a drill, emery cloth (120) grit, and a cone wire 1 inch brush so you can clean the top of the cylinder. You will need some black silicon to put the 2 halfes of the engine back together!!