1953 Johnson RD-14 25 hp - spark plug will not tighten

[mstone1968]

Hello,
I changed spark plugs in this motor today and while turning the top spark plug it will tighten up then gets loose. I can't tighten it so that it locks in place. I got the motor to fire up and was working on adjusting the carb settings. Engine was running fairly smooth for approx 10 seconds -revved up - backfired really loud- and the top spark plug shot across the yard?? The spark plug is the correct size and will tighten to a point then just goes loose. Will not stay tight. The one that was in there before changing them was very tight and did not have a problem. Now it will not tighten? Would anyone have any suggestions on what would cause this. I don't see how I could have stripped it or anything because I made sure to not over tighten. I am planning on doing a compression check this weekend. Any help would be greatly appreciated

 

[samo_ott]

Re: 1953 Johnson RD-14 25 hp - spark plug will not tighten

It's stripped. Use a heli coil to fix it. Most auto stores sell em. Basically you replace the threads with new threads. The old threads probably came out with the old plug.

Or worst case scenerio, take off the head and take it to a machine shop to fix or lastly, buy a new head.You could try aomci.org and post an ad if need be.

And it's unlikely you'll be able to do a proper compression check like that until the top plug is fixed.

 

[F_R]

Re: 1953 Johnson RD-14 25 hp - spark plug will not tighten

Take the head to an automotive machine shop for repair. They do it every day. If you attempt to do it yourself, you need to buy an installation kit. You will need a new head gasket to reinstall.

 

[JB]

Re: 1953 Johnson RD-14 25 hp - spark plug will not tighten

A Time-Sert is a better solution than a helicoil. See if the machine shop can do that.

 

[mstone1968]

Re: 1953 Johnson RD-14 25 hp - spark plug will not tighten

Hey guys,
Thanks so much for your help. I will take it to a shop this weekend. I'm glad to hear that it can be repaired.