Triumph t140 heli coil

[popstar1]

Many years ago a friend of mine (claimed) he had his old Bonneville spark plug thread drilled  out and heli coiled with the head still attached to the barrel, by pushing a greased length of cloth( to catch the swarf)into the combustion chamber (though the spark plug hole) it was drilled to the correct size then  heli coiled, the tang was somehow removed then job done, is this really possible because mine needs doing on the left pot.The bike was running really well, I wish I had left it be!

[Rex]

Sounds a bit far-fetched to me, but years ago I had an XS 250 where some tosser had cross-threaded one of the plugs but kept on winding anyway, which left an extremely tight plug sitting cocked at a funny angle and nowhere near seated correctly.
As it was cheap (XS250s always were as they were crap of the highest order) and I neither wanted to spring for a gasket set or new cam chain, I took a 14mm spark plug tap, coated the flutes in heavy grease (to catch the swarf) and wound it in at the angle it should have been.
Piece of pee as the alloy was so poor and soft and the bike was running again in no time.
You could do much the same with the helicoil tap but it's always a risk, although if something breaks or goes wrong and the head then has to come off then you're no worse off.

[L.A.B.]

I'm sure it's possible but there are stronger more secure spark plug inserts available now which don't have the tangs which could potentially drop into the cylinder.

(Examples)
http://www.motorcycleclassics.com/mc-how-to/spark-plug-rethread

http://www.timesert.com/html/howtosp.html

[popstar1]

The timesert looks to be my best bet and the  instructional video is excellent , I have checked online for a kit with a 14mm diameter tap and a1.25 thread pitch but  unfortunately it looks like you have to buy an entire kit which runs to £100 to get the thread size I want , does anyone sell a thread specific kit ?

[iansoady]

I've heard of lots of people doing it but my approach would always be to get the head off. I appreciate it's a bit of a faff but then you'll know there are no nasty bits dropped in. Plus you can check valve seats, guides etc.

Maybe not of course if it's your daily transport.......

[murdo]

I have seen the single inserts on fleabay, and not real expensive.

[popstar1]

 Yes I have but of course you need the applicator as well and the cutting tool. I may have to open the wallet !

[L.A.B.]

Yes I have but of course you need the applicator as well and the cutting tool. I may have to open the wallet !

There are cheaper insert kits available but I couldn't say how good they are.

http://www.ebay.co.uk/itm/14MM-Spark-Plug-Helicoil-Thread-Insert-Reamer-Tap-Repair-Kit-with-4-Inserts-/232115831263?epid=1064242054&hash=item360b2e81df:g:UGgAAOSw-CpYA5YH

[chaterlea25]

Hi,
I would find some body who has the time sert kit and the experience to do the job in situ
If you were local to me I could do it 
I use compressed air and or vacuum plus a boroscope to look inside the cylinder to make sure theres no residue
left inside

John

[popstar1]

Thanks folks.i will sort it before we run out of summer.

[popstar1]

 Just as a matter of interest I have purchased an endoscope from eBay for £7 it fits directly onto your phone has a magnet attachment periscope attachment and also various other tools this particular one is waterproof too. 7mm Dia smaller ones are available for the same cost.

[L.A.B.]

The swarf from the thread cutting will be aluminium, so any wayward chips that manage to drop into the combustion chamber aren't likely to be a problem. I've heard the image quality of those cheap cameras isn't all that good. 

[popstar1]

I purchased a taper and tap from E bay M14 X 1.25mm last week , I cleaned the threads up this morning and took the bike out for a run of about 10 miles and all seems well! No leaks , I am not suggesting that this is a long term solution but the old girl is up and running again.