Hello,I was trying to do a good deed for my sister-in-law by Serviceing her old Deere that has a 15.5 horse Koyler.I pulled old plug out .It was a little stiff coming out.I had the wrong new plug.So I decided to install old plug back in.Well,I can't get it to screw back in.It will start then stop's.Looking at thread into head it look's like it is messed up.I'm going to get correct plug before going any farther.Any suggestion's on what I need to do?
If it is not too bad you can get a plug thread repair tool to clean up the threads.
Two types and the ones that expand are better than the plain tap type as you install them small then thighten up and screw out thus dragging all of the rubbish out
Yes, and a little more on the clean- out style. They have little scoops to allow the crud to accumulate as you slowly turn them in and out BY HAND. Examine the threads on the plug to be sure they are proper and not irregular and that the lead thread is there ( the first thread which ends and should have a distinct starting "profile" to engage.
A standard tap will remover base material which can enlarge the female threads (not good). There are special "chaser " taps which would roll and restore the original threads, but they a search exercise and expensive. The best bet is careful work with the (typically) two headed clean- out variety with the scoops. The two heads are two different thread sizes and this style often has a hex built in the middle which will accept a socket (go easy). Make sure you are "square" when starting these taps . It is easy to mistake resistance when starting with "crud," but if not inserted into the centerline of the threaded bore it is possible to ruin the head with a cross-tapped bore. Then it is heli -coil time.
The expandable type Bert suggested works very well, but you must take your time. AutoZone lends out tools at no charge, you may want to check to see if they have one. Another place to borrow one is your small engine repair shop or auto mechanic. If you do get one there, make sure you show your appreciation.
