A bad Saturday afternoon - plug threads

tail_heavy · Jul 17, 2006

I was checking my plug condition as part of my attempts to get to the bottom of my rich running problems. Nr. 1 was very stiff all the way out and, sure enough, shards of alloy came out in the thread. The plug thread itself seems crimped up (the first two threads near the electrode are closed up for about a third of the circumference). Engine was cold BTW.

This was the first time I have removed the plugs myself - having decided to take over maintenance of the car after several fruitless attempts to get 'specialists' to sort out the engine management probs. One of the specialists should have removed the plugs twice and the other once, during the course of their researches, so I guess one of them is to blame for this, presumably the last one to touch the engine - but I don't see much ponit in trying to get any redress, it's not very easy to prove.

No, the reason I asking is just to check out other's experiences with this problem. I know I have to pull the engine and get the plug thread helicoiled, but surely (I said, trying to kid myself), if I clean up the thread with an old plug with grooves cut in and am lucky enough to get a new plug to sit, I can at least get a few more miles out of the engine before I face the inevitable. I mean, wouldn't the piston just blow the soft alloy shards out of the exhaust port with next to no damange to the rings and bores?? As I said, I'm just trying to kid myself, I know what it is that I have to do.

bones · Jul 17, 2006

Sorry to hear that Richard, you know the answer drop the engine and get it fixed, the damage might already have been done regarding metal shavings into the bores as you don't know exactly when it was done. As a boy I've run inexpensive two stroke engines with cross threaded plugs and they were ok but then the pistons only lasted a few thousand miles anyway, find someone good to do the head repair or get a second hand head and have both heads revalved if the valve seals are not great.