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Oh no, stripped spark plug thread!

Discussion in 'Technical and Troubleshooting Torque' started by davesta, Apr 16, 2008.

  1. Hey everyone, just did a spark plug change on my bike and one of them is stripped. I screwed both plugs in with my fingers only, then torqued with a torque wrench. Except one of them won't torque at all. Gets to a point, then just 'lets go'. The old plugs are Denso X24EPR-U9 (standard spec plug). However i noticed that neither of the old plugs have washers on them. My dad (a former mechanic) thinks that someone in the past has overtightened the plug and has then taken the washer off to try and get a little more thread. I'm not 100% sure yet if the denso plugs are supposed to have washers, but i'm pretty sure they are. I also noticed that the original spark plug that stripped wasn't done up very tight when i unscrewed it. So it looks like some bozo in the past has done a dodgy on me (considering i have a fully stamped logbook could prob narrow it down to 1 or 2 shops). So....
    What is a normal course of action to follow now? Helicoil? I'm guessing i need to remove the head for this? Is there any other remedies i can use? Can anyone suggest a good mechanic/workshop/engine builder? I'm not really interested in a dealer (unless someone has a special recommendation). I;m just after a good, independant place that knows their stuff, does a good job and charges a fair price. Anyone have any ideas? Thanks so much :grin: :(

  2. I think I'd cry.

    That's very sad.

    I think your dad picked the right answer in one about the washers - they should always be fitted.

    How do you know a PO didn't change plugs and strip the threads. I wouldn't start blaming a shop just yet.

    Helicoil or similar is the only answer. A lot of guys reckon you can do it in situ (with the head in place) by using grease on the tap to catch the swarf.

    I wouldn't do it. You don't need much swarf to ruin a good bore.

    All the best

    Trevor G
  3. I knew you'd reply Trev, thanks mate! Yeah i'm ready to cry haha. Yeah i was expectng i'd have to pull the head off. If i'm capable that is. Worst case scenario is i have to drop whole engine out and take it in. Oh well, at least it'll give me a chance to put a thinner head gasket in and maybe some mild porting and maybe some new valve stem seals (uses a bit of oil like most trx's). Any ideas on good shops??
  4. I would cry as well :(

    A helicoil is generally stronger than the original, although can be expensive. Someone who was very good at it may be able to do it without removing the head, however I would suggest just removing it for peace of mind.

    Sucks to have something good ruined for no good reason :(
  5. Well its possible, although there is only 1 PO and i know him reasonably well. He's a fastidious SOB so i can't really imagine him a) stripping the thread (thats more my style :LOL: ) b) doing a dodgy job to cover it up c) selling the bike to me without telling me. Although you never know. But thats why i'm not posting up the 2 dealers that *could* have done it, cos i have *zero* proof. I'm just pissed cos some tool has buggered my bike and is gonna cost me a bit of time and money. Grr.
  6. I can narrow it down.

    It will be the dealer that did the service that required the removal of the plugs.

    Not all services do.
  7. I've done helicoils in situ. The kit (for 14mm plugs) was about $100 (from memory).

    Lotsa grease on the tap caught everything. If you're really paranoid, set the piston to about 3/4 of the way up the bore on the compression stroke (valves closed) and fill the cylinder with grease. Then, when you're done, rotating the engine forward will expel the grease and any stray swarf.

    It's worth bearing in mind that the swarf produced is coming from a soft aluminium cylinder head and so has all the scoring power of a nice gooey Camembert :grin: .
  8. yeah the nose picker fraternity used to so their helicoils in situ all the time. It's no ideal, but saves a lot of hassle.
  9. I'd like to emphasise that I probably wouldn't try it with an iron head unless I was desperate. Iron swarf would be vastly more likely to cause problems in the cylinder, being so much harder than ally.

    But then, it's pretty academic as there hasn't been an iron headed bike for 25 years (as far as I know) and I've never seen a damaged plug thread in an iron head anyway, in spite of coming across the odd plug that needed a 2m breaker bar to loosen :shock: .
  10. BTW, who are the nose picker fraternity?
  11. Trail bike riders
  12. Yeah i thought that too, but not much point now, all i know is that i'll prob never take any bike to a $tealership to get serviced (no apprentice is touching my bike!).

    I definitely won't be doing this myself, i'm ok with simple stuff like oil changes and the like, but i wouldnt wanna f*ck this up. I might try pete the pom and see if he can help. Do you reckon i could safely ride the bike a short distance (say less then an hour) if i tightened the stripped plug as much as i could (impossible to overtighten, obviously) and took it pretty easy? It's probably been sitting in there at a less then optimum torque for the last 5 years so i'm hoping it would be ok. I'd love to avoid having to remove the head myself if i can, might be a bit above my comfortable skill level. Thanks for all your help, guys. What seemed like the biggest emergency in the world last night has receeded to a mere, mammoth PIA. :cool:
  13. If you're capable of removing the head, I'm willing to fit the hellicoil ... as long as you are willing to leave it with me for the day.
  14. Thanks VCM!
    pm sent