So I have a sick 441 in the shop that's here for some medicine. The major problem with the saw is that the spark plug threads are stripped and no longer hold a plug securely. So we's a gunna do sumthin' about it. (There's more to do with this saw but you guys are gonna have to wait for it. ) The kit I use to repair stuff like this is a HeliCoil brand Sav-A-Thread like this one. http://www.ebay.com/itm/HeliCoil-Sav-A-Thread-14-x-1-25-Spark-Plug-Repair-Kit-/320678533389 This is a far better repair than the coiled wire style, especially where there is so much heat and vibration. Also a spark plug hole gets the plug inserted and removed fairly frequently. I always remove the cylinder to do these, there is NO way to prevent every shaving from falling into the engine. Even greasing the tap, you just wind up with a wad of grease on the inside of the cylinder, just off the edge of the plug hole, right where you can't see it. Here is what the tap looks like if you've never seen one. Once the cylinder is off, tapping the hole goes just like any other similar repair. The finished hole. The insert is pretty simple, except that it has the top three threads knurled so that when you expand the insert in the hole, it cannot back out. I coat the insert with Dirko HT sealant and thread it into the hole by hand. Once it's in you use the special drift in the kit to expand the insert and you're done. Finished product. This type of repair works for a lot of applications, spark plugs especially. It works on either the gasket-ed or tapered seat type.
I used that same kit to repair my MS361, with some flavor of Loctite instead of the Dirko. I haven't put a whole lot of hours on it yet, but so far so good. The other kit I read good things about was Timesert. Their tooling is much more expensive.
Maybe worth noting that on some saws it's important to be careful of the decomp valve when tapping out the hole. I accidentally depressed the button on mine and then ran the tap right into it.
Yes they are, and supposedly it's an even better repair. Maybe if the part I was repairing was a little more expensive it would justify the TimeSert kit but I don't own any Fords and the HeliCoil kits work fine if you are careful to get the insert positioned and seated properly. Good tip!
I glad to hear you recommend these for saws, I only used one of these once on "66" Dodge Coronet (push button transmission) back in the mid 70's. I have a beater 390 that a neighbor gave me in exchange for some firewood (I just wanted to give him the wood for free but he insisted on giving me something for it!). It has a stripped plug hole and needs a few parts. I've been planning on pulling the cylinder on it to see what its like before deciding which way to go................... junk/new cylinder/heli-coil.
Looks like a fantastic repair !! Thanks for the step by step with pics . This info will come in handy for many
Actually I'd like to do a sub-forum with just how-to posts. Too many stickies and navigating the main forums gets inconvenient. Besides, who reads the stickies anyways?
i stopped using heli-coil a long time ago in favor of the time sert. I even make my own time sert for things such as a case.
That's the exact inserts he used. I'm thinking he had it in cockeyed or something when he ran it in and crushed the knurled threads when he expanded it because the plug wouldn't go in smoothly and once the plug was in and seated, it leaked compression air badly. No wonder I couldn't get the saw tuned......
I did end up putting one in that 390 pictured above and it worked out perfectly. Used a generous coating of the red Permatex Ultra Copper Max Temp stuff on it and cleaned up the excess when done. I don't know if that was the "best" stuff to use but so far so good!
I put one of those on a 361 the other day. It was the first time I used that style. I feel a little relieved that you used one.
I've used time-certs on KLR650 drain plug holes. Usually what happens is some goof ball buys a $9 harbor freight torque wrench and gets the bright idea of using it on the oil drain plug...
