No3 spark plug thread stripped

[Mowjoe]

Though I'd treat the old girl to a new set of Densos for the weekend.(anything for a quiet life). Unfortunatly the new plug into no3 kept turning! Removed and found bits of ancient thread on the plug. Question is can I fit a helicoil without taking the head off and if so is there a kit out there that can be recommended to do it?

[PAULJAC47]

Head off... dont be tempted to try and helicoil with head in place,asking for big trouble, if a bit of swarf get down there you will be talking BIG probs.......

[DavidZ1R]

My Z550 project had exactly the same problem, on the same cylinder, the previous owner left the plug in sealed, when I took the head off the piston was pitted to fcuk, new piston and rings, then I had the thread helicoiled, been ok to date.

[z1bman]

i have done quite a few with the head on without any problems. set the piston to top dead centre with the valves closed. fill the cylinder with brake cleaner & blow dry with compressed air do this a couple of times. tap the thread with the heli coil tap or an equivalent thread repair kit . do not use grease on the tap once the tap has cut the thread use a vacuum cleaner with one of the adapters from an air bed pump these will fit inside the thread. when this is done lower the piston slightly so you can see the top of the piston to make sure it is clear of swarf then insert the heli coil

http://www.ebay.co.uk/itm/BRAND-NEW-15- ... 1e88b505d5

vacuum cleaner hose with air bed adapter fitted




http://www.ebay.co.uk/itm/12V-Electric- ... 51b9a837b9

[Mowjoe]

Great advice guys as ever.

[andyb1962]

My number 3 thread is a little iffy slack at top but tightens ok at middle of thread down to its seat. It's one of them jobs I'm always gonna do.
Think I'd be worried bout it without the head off but it sounds easy enough
Might tackle it this winter .
Great advice Z1b man

[CAT3]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

[Mowjoe]

We can start a 'Slack no3 plug'ole club!

[zed1015]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

If you haven't got a steady hand you need to use a kit with a pilot tap that follows the remains of the old thread and cuts a new one for the insert.

LIKE THIS.. http://www.voelkel.com/en/produkte-en/g ... er-en.html

[Mowjoe]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

If you haven't got a steady hand you need to use a kit with a pilot tap that follows the remains of the old thread and cuts a new one for the insert.

LIKE THIS.. http://www.voelkel.com/en/produkte-en/g ... er-en.html

so no drilling requirement for this type of tap?

[andyb1962]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

If you haven't got a steady hand you need to use a kit with a pilot tap that follows the remains of the old thread and cuts a new one for the insert.

LIKE THIS.. http://www.voelkel.com/en/produkte-en/g ... er-en.html

so no drilling requirement for this type of tap?

That's what I thought when I looked at it !

[Mowjoe]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

If you haven't got a steady hand you need to use a kit with a pilot tap that follows the remains of the old thread and cuts a new one for the insert.

LIKE THIS.. http://www.voelkel.com/en/produkte-en/g ... er-en.html

so no drilling requirement for this type of tap?

Pilot Nose taps have been developed for the repair of damaged sparking plug threads without the need for additional drilling.

This type of tap uses the original thread to guide the tap. It has reamer faces behind the pilot thread which cut the hole to size prior to tapping of the wire insert thread form.

They are simple and easy to use and in 1 single operation ensure that the wire insert thread is concentrically aligned to the original thread.



http://www.ebay.co.uk/itm/M14x1-25-Spar ... 483dd2998f



That's what I thought when I looked at it !

[Mowjoe]

Sounds like I know what I'm talking about! The above was from that eBay ad if you scroll down

[zed1015]

Take the head off & do the job correctly, you know "Sod's Law says ........ "
It's impossible to hold a drill square to the job & do the tapping square too, by hand, with the head in place. No doubt some on here have "successfully" done this task in situ, but I wouldn't dream of it !

If you haven't got a steady hand you need to use a kit with a pilot tap that follows the remains of the old thread and cuts a new one for the insert.

LIKE THIS.. http://www.voelkel.com/en/produkte-en/g ... er-en.html

so no drilling requirement for this type of tap?

Yep! No drilling required as you have discovered in the ebay ad.

Just go slowly , set the piston as close as to tdc as possible while the ex valve is still open and periodically give it a blow out with the air line.

Lightly use some cutting fluid on the tap but not grease that can stick swarf inside the cylinder and prevent it from getting blown out.

[PAULJAC47]

As i said take the head off,one plug No3 again, is crappy on my bike but holding ok for now i would be worried that some swarf could be missed as well as the little tang off the coil, come Winter i will take the head off and do it properly and replace stem seals and check out all the other gubbins at the same time just my two penorth...