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Stripped spark plug

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by mrp, Jul 16, 2007.

  1. I went to change the plugs on my bike yesterday and found one of them to be a different sort of plug which had a metal bracket like thing making it screw in much less deep. It was forced in quite obviously and here I am left with a screwhole which only lets my NGK plug go in barely half way.

    After some hiccups and troubles with idling my dad got it to run better by making the gap in the plug wider, we saw this on the old plugs to. Now it idles alright but I doubt it's sparking properly on that plug. I've had really bad fuel consumption (like 110k) up till the change and am still on the new tank.

    Any advice? I've read stuff about helicoils but no idea how to use one and don't know what tools you need. Bike is an 89 fzr250

    thx in advance, mrp
  2. Do you think its a washer off an old spark plug that got stuck?
  3. Very common problem with the FZR250's... alot of DIY mechanics get this wrong... I cant remember if it is no2 or no3 but there is just not enough space to hold the spark plug straight and worst yet it will go on an angle up to a cetain length...

    Heli coil?? will not work as the design of it will not permit the spark plug to go right through... it has the "tab" at the botom which you can brake off but who wants to have a posibility of a metal bit falling into the cilinder...

    There are other alternatives but there are drills and $$$ involved...

    The solution I have found in the past is simple and not to costly... get the right tap (as in dye and tap set) avalable from some Auto tool shops or even bolt and nut joints... with a whole heap of grease on it just refresh the threds... all you will need to refresh is about 3mm to 5mm of the thred.. the rest will hold the plug sufficently...
  4. Either will work, but either has the risk of bits of metal into the cylinder. At least with the Heli Coil there's only one bit of metal to take care of, using a tap to re-cut the thread will put a load of metal shavings in the cylinder. If you're not certain, definitely a job for a professional, because messing it up could mean big $$$ engine damage.
  5. I'll have a look in a cattledog i've got at work tmw , I'm sure I saw a new tool on the market that not only restores spark plug threads but also catches the swarf etc.
  6. Be interested to see a pic and details of this critter VTRBob :grin:
  7. sounds like a lifesaver, for my sake I hope you find it :D
    I heard if you put shitloads of grease on the helicoil or whatever it will catch the metal shavings... I don't know how foolproof this is though
    and hotcam I don't really know cause it's hard to get a look in there and I'm kind of hoping to ignore it so it will go away :p

    damn quotes don't seem to like me on this forum..
  8. Found the cattledog and now the right webpage :grin:

    14mm Back-Tap Spark Plug Thread Repair Tool

    The Back-Tap 's patented collapsible design allows it to be placed through the spark plug hole and into the chamber.
    A mandrel is then drawn back, expanding the tool 's threaded area and threading into the clean threads at the bottom of the spark plug hole.
    The Back-tap repairs the damaged threads as it is drawn up through the spark plug hole, bringing debris and metal filings with it

    In the cattledog they are listed at $36 inc gst
  9. VTRBOB.... I love you :p

    Now I just need to get my hands of one of these suckers. I emailed them so hopefully I'll get a reply soon. Are you sure the size is 14mm though? I'm new to bikes so I don't know if theres a standerd or anything. Ill get my googlefu rolling on that one.

    Once again thanks for filling me in on this product, it's a golden solution :D

    edit: I found out from http://www.sudco.com/spark.html that the thread size is 10mm.. I guess that means it doesn't fit right? :(
    damn I guess I gotta do this the hard way :/
  10. You don't have much choice but to remove the head and do the job properly. While the head is off helicoil all the plug holes. A 10mm plug will not give you enough room to insert a helicoil while the head is on unless you can find some thin strong pointy nose pliers to pull the tang out with. I have repaired many plug hole threads while leaving the head on. I would try buying a tap first and if that does not work then pull the head of.