MaineDad 85 #1 Posted June 28, 2011 OK, Here's a new one for me. I used the C-120 for the first time since I cleaned up the carbon when I removed the head. I mowed for about 2 hours when near the end, i started loosing power. I finished the mowing and let it cool down a while so I can take the plug out to see if there was any oil inside. The plug came out hard and too my surprise the threads were much bigger! I put the plug up to a new one and yup it was about a 1/3 larger! The spark plug hole is now too big for a new plug. It's an aluminum head if that helps. Any thoughts? Dang!!!!!!!!!!!!!!!!!!!!!!! Share this post Link to post Share on other sites
rmaynard 14,922 #2 Posted June 28, 2011 Sounds like when you took the plug out, a helicoil came out with it. You should be able to put it back in with the helicoil on the plug, but if it were me, I would get a new helicoil, and a new plug. Put the new helicoil back in the head and install a fresh plug.. Share this post Link to post Share on other sites
WH854 44 #3 Posted June 28, 2011 Could be it was heli coiled Chas Share this post Link to post Share on other sites
WH854 44 #4 Posted June 28, 2011 Sounds like when you took the plug out, a helicoil came out with it. You should be able to put it back in with the helicoil on the plug, but if it were me, I would get a new helicoil, and a new plug. Put the new helicoil back in the head and install a fresh plug.. Beat me to it Chas Share this post Link to post Share on other sites
MaineDad 85 #5 Posted June 28, 2011 Took the head off and it was heli-coiled, and there was oil on top of the piston and all over the valves. Started the tear down already Machine shop here I come... Share this post Link to post Share on other sites
dgoyette 12 #6 Posted June 29, 2011 Dang is right Micah! Share this post Link to post Share on other sites
Electro12WH 50 #7 Posted June 29, 2011 I had a head that did that, but it was a threaded insert, not a helicoil. I put some red loctite on it, reinstalled it, and then screwed the spark plug out. Share this post Link to post Share on other sites
shorts 182 #8 Posted June 30, 2011 change from a helicoil thread repair insert to a keensert thread repair insert that has pins that you use to stake the insert inplace to prevent it from coming back out. follow the directions on the package, the helicoils use a special tap and the keenserts use the next larger standard tap IIRC Share this post Link to post Share on other sites
MaineDad 85 #9 Posted June 30, 2011 Thanks guys. I am going to buy a new head just to be safe... Share this post Link to post Share on other sites
SousaKerry 500 #10 Posted June 30, 2011 Heads are plentiful and cheap but I would always use a keensert, we use them here at work on new equipment even. Especially if it is an aluminum part that we know will be disassembled frequently. keensert installation instructions Share this post Link to post Share on other sites
