Blackhood Bill 720 #1 Posted January 13, 2019 (edited) Ok my question is this. Spark plug blew out, dad replaced head, spark plug blew out with used head, put heli-coil in, spark plug blew out again! Tonight pulled head gasket looks good. Would you replace gasket and what would cause this? What needs to be checked and where to start? Pics of gasket with head off attached. Any all help appreciated due to snow has finally arrived. Ordered new head and gasket. This is on a C-145 hydro, Kohler 14 hp K321AS engine with proper spark plug H-10 Edited January 13, 2019 by Whnewone Added info Share this post Link to post Share on other sites
oliver2-44 8,852 #2 Posted January 13, 2019 @Whnewone Please share a little more information. What tractor and engine is this, and what brand & part # spark plug are you using. Is there a chance you are using an incorrect plug. Share this post Link to post Share on other sites
ztnoo 2,298 #3 Posted January 13, 2019 That's pretty strange. Never heard of that problem before ..... even in Indiana. Especially in Howard County! Share this post Link to post Share on other sites
Blackhood Bill 720 #4 Posted January 13, 2019 This is on a C145 hydro 14 hp Kohler K341 AS engine with H-10 spark plug. Share this post Link to post Share on other sites
ztnoo 2,298 #5 Posted January 13, 2019 A K341 is 16 hp. Share this post Link to post Share on other sites
richmondred01 2,205 #6 Posted January 13, 2019 Also check the reed valve assembly. You may have too much pressure build up along with bad plug threads. also make sure the oil drain hole on the cover is facing down. 2 Share this post Link to post Share on other sites
Blackhood Bill 720 #7 Posted January 13, 2019 Oooops my bad it's a K321 Share this post Link to post Share on other sites
c-series don 7,815 #8 Posted January 13, 2019 I don’t know the answer to this, but I want to!! Share this post Link to post Share on other sites
The Tuul Crib 7,332 #9 Posted January 13, 2019 Is it possible that the exhaust valve maybe sticking causing The spark plug to pop out? Share this post Link to post Share on other sites
Howie 882 #10 Posted January 13, 2019 I would think the plug is not really tightening up as it should. Helicoil put in straight so plug seat correctly? 1 Share this post Link to post Share on other sites
Howie 882 #11 Posted January 13, 2019 If exhaust valve is not seating it would build less compression than if it was seating I would think. Share this post Link to post Share on other sites
Blackhood Bill 720 #12 Posted January 13, 2019 To my knowledge yes had that installed by a mechanic who does nothing but work on garden tractor engines. Share this post Link to post Share on other sites
ztnoo 2,298 #13 Posted January 13, 2019 The intake valve is open in the pic, so the combustion chamber would be "vented", although the wrong way. That wouldn't blow a plug out. Unless both valves would not open, its either a problem with the heads (highly excessive compression ratio), the plug threading, or the spark plugs themselves. Was the head torqued to spec? Share this post Link to post Share on other sites
Blackhood Bill 720 #14 Posted January 13, 2019 That I don't know due to that was done before I even took possession of the tractor. Share this post Link to post Share on other sites
Howie 882 #15 Posted January 13, 2019 I'm still leaning toward the threads in the head or on the plug, because if it was making that much compression would be real hard for starter to turn it over. 2 Share this post Link to post Share on other sites
Blackhood Bill 720 #16 Posted January 13, 2019 Turned over fairly easy and fires right up Share this post Link to post Share on other sites
Ed Kennell 35,798 #17 Posted January 13, 2019 Time for a compression check. If the correct plug is seated in a good threaded hole, it would require over 200PSI to blow out the head threads. 2 Share this post Link to post Share on other sites
Blackhood Bill 720 #18 Posted January 13, 2019 After pulling head off the threads are now gone. Will have to do that when new head arrives. What should the compression be? Share this post Link to post Share on other sites
ztnoo 2,298 #19 Posted January 13, 2019 6.6:1, 7:1 or 9:1 (See note 8 Ê) Note 8 - Compression ratio depends on which cylinder head is used. * http://gardentractorpullingtips.com/engine.htm Share this post Link to post Share on other sites
Shynon 7,435 #20 Posted January 13, 2019 You will need to do a leakdown test, ACR will not allow for a compression test. Has the block been sleeved? Reason I ask is the ledge around the piston that is lower than the top of the cylinder and the piston if off center. Something just doesn't look right. Share this post Link to post Share on other sites
Blackhood Bill 720 #21 Posted January 13, 2019 If it has I don't know but that would something to look at for sure. Will have to take gasket off and clean it up for examination. Share this post Link to post Share on other sites
lynnmor 6,783 #22 Posted January 13, 2019 Are you using starting fluid? Share this post Link to post Share on other sites
953 nut 51,721 #23 Posted January 13, 2019 9 hours ago, Whnewone said: After pulling head off the threads are now gone. Will have to do that when new head arrives. What should the compression be? Sounds like the mechanic that installed the head owes you a refund on that job. Spark plugs stay screwed in to high performance engines with very high compression, they should stay in a good head on a Kohler. Your engine has an automatic compression release that makes the engine easy to turn over at low RPMs. 3 Share this post Link to post Share on other sites
squonk 38,937 #24 Posted January 13, 2019 53 minutes ago, 953 nut said: Sounds like the mechanic that installed the head owes you a refund on that job. Spark plugs stay screwed in to high performance engines with very high compression, they should stay in a good head on a Kohler. Your engine has an automatic compression release that makes the engine easy to turn over at low RPMs. Share this post Link to post Share on other sites
Blackhood Bill 720 #25 Posted January 13, 2019 No starting fluid. Never had to ever since I have had it. Share this post Link to post Share on other sites