Honda GCV170 / HRN216VKAA - Can't Pull Cord Due to Compression

eledford

Forum Newbie
Somewhat new but willing to put the work in. Here is the story behind the mower:
The mower was working great and all of a sudden chugged loudly at a reduced very low RPM. I checked the oil (which was very low) and added oil. Pulled cord and continued to chug loudly and at a very low RPM. After a few starts the pull cord would build up compression and be super hard to pull. With constant force it would eventually release and rotate a couple spins before building up compression again.

Things I've tried so far:
- Removed the starter coil housing to make sure the rope pulls freely when disengaged from the engine. It does.
- Checked that the flywheel nut key looked intact - was able to remove the flywheel nut but not able to remove flywheel. Key looked like it was good.
- Checked that there is enough gas and gas was flowing.
- Removed all oil and added 12oz of fresh oil.
- Checked that nothing is stuck in the blades and cleaned bottom of deck.
- Cleaned carb
- Removed the spark plug & pulled the cord a few times to see if there was oil in there -- nothing came out. The cord pulls easily and completely when the spark plug is out. As soon as I put the plug back in, the problem reoccurs.
- Replaced spark plug. Prior plug end was covered in black soot.
- Checked the filter. Little dirty but serviceable. Also tried to start with filter off.
- Adjusted valves to .1mm

After the valve adjustment the the cord initially pull fine but couldn't get the engine to turn over (might have chugged a couple times before dying). After about 10 pulls the compression problem returned.

Would love to hear any other ideas?
 
Just try to remove the flywheel. Even if the nut key looks OK, without removing the flywheel = nono. Had the same problem with a push mower with a (think) GCV 160 engine. After the flywheel removed, I saw the damaged key. Greets.
 
The gcv160 has a plastic camshaft pulley and a rubber belt to time the valves. You would have seen it when you adjusted the valves. Take a good look at that pulley and see if it is damaged. I think it also controls the compression release function. That might answer both the poor engine performance and the stuck compression.
 
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