Heli coil questions/help.

[opposedtwin]

My FD-12 has been a great runner as recently as last summer-ALL summer. Today I pulled it out of the basement to get it ready for the year and had trouble starting so I put in new j6c plugs. One went in a bit mushy. Not cross threading, but mushy. I guess I don’t remember a helicoil having been in there but it disintegrated and needs a new one. So in all these years I’ve never done a helicoil. What size do they go buy? Size-thread pitch like a bolt? So a spark plug looks about 9/16-18?

I guess I’ll watch a couple you tube videos but would sure like to hear advice from my fellow members too.

Also when I primed the tank, the fuel filter bowl filled up and started leaking a bit. I replaced the rubber gasket with a new one but that one is seeping fuel a bit too. I bought them from a reputable supplier on this site. ???  But I don’t believe the plugs are getting fuel anyway. I suspect my float needle is stuck closed. Will have to investgate.

As always thanks for any and all help!
Scott

• This topic was modified 2 years, 8 months ago by opposedtwin.
• This topic was modified 2 years, 8 months ago by opposedtwin.
• This topic was modified 2 years, 8 months ago by opposedtwin.

[Buccaneer]

Fore whatever reason, our spark plugs have been sized
metric for a long time. Yours will be the 14 mm and the larger
plugs some older motors take are 18 mm.
Seems that was was a recent post about sparkplug heli-coils, the
good, the bad, and the ugly, so you should be able to search
on site for info.

 

Prepare to be boarded!

[opposedtwin]

I’ll give it s shot.

 

• This reply was modified 2 years, 8 months ago by opposedtwin.
• This reply was modified 2 years, 8 months ago by opposedtwin.

[Mumbles]

You should use the proper Heli Coil steel inserts intended for spark plugs instead of the wound wire Heli Coil inserts which are good for bolts and machine screw threads.  The steel inserts lock into the head while the wire ones don’t and are sealed using red hi-temp silicone.

New threads are cut into the head using the special tap supplied in the kit, sealer is applied before winding the insert in and then it is staked to the head using the tool supplied.  To get the insert in straight, it’s best to remove the head and using a drill press, start the tap by hand and finish using a  wrench or a socket.  This method only works on heads with the plug pointing straight out and not on an angle.  The threads could also be repaired without removing the head but you’ll have to make sure the tap starts into the head straight and lots of light grease is used to prevent any chips from falling into the cylinder.

• This reply was modified 2 years, 8 months ago by Mumbles.
• This reply was modified 2 years, 8 months ago by Mumbles.
• This reply was modified 2 years, 8 months ago by Mumbles.

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opposedtwin

[billw]

I went ahead and bought one of those kits but haven’t tried one yet. I would not have bought it if it was not branded genuine Heli-coil.

Long live American manufacturing!

[opposedtwin]

Thanks mumbles! These plugs are at an angle. Typical of later, higher hp OMCs. I’ll track down a kit and see how it goes. Worst case scenario I’ll need a new head.

[Author]

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