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prouddad90
10-27-2017, 07:30 PM
need help with my Z. it was running great an had no issues. an i shut it off an then tried starting it back up an it had no compression. i could (kick it over by hand) what could cause that.

mostlyxs
10-31-2017, 03:02 PM
Hello prouddad90
I recently had the same experience with my 86 YFM225, running great, circuited the neighborhood, drove it up to the door to the barn to let it cool down before pushing
it inside. Decided to make another round with the experimental muffler insert I'm developing, and it would not start. Pulled it over with the rope, seemed rather weak.
Pulled the plug, and compression pressure was 35#, Not sure how it could have been running as strong as it was ... let alone start!
I pulled the top end, and the rings are really seized flush in the grooves! Unbelieveable! Cannot understand how it can go from one extreme to the other.
Ordered in new standard rings, full gasket set (couldn't find top end sets), cleaned it all up (scraped out the grooves, of course) touched up the valves and lapped them.
Reassembled things with plenty of oil, set the valves, etc, etc. Checked the compression: 135# Started up first try, warmed it up, easy on the throttle, gently made my 1 mile test loop
and runs great. This machine sat in a shed for twenty years or more before I got it earlier this year, so no telling the internal condition, nor the chemicals remaining inside
after I changed the oil during initial prep.
Before I reassembled it, I checked the old and new ring gap in the freshly honed cylinder, just to confirm it had not been slightly bored and the factory piston reused, and confirmed it was a standard bore.
The new & old ring gap was virtually the same!. Perhaps someone out there can shed some light on this! Before I ran it the first time, the compression was 115# with oil squired in cylinder.
John