Spark Plug Thread repair

  1. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    Has anyone had any luck with the very cheap nasty spark plug repair kits like this? http://www.ebay.co.uk/itm/VORLUX-SP...642910&hash=item2125f7d34a:g:AScAAOSws4JW8RgS

    I've been asked by a friend if I can sort out an off road go kart thing based around a Chinese pit bike engine. First (and maybe the only) problem is that the spark plug threads are stripped. I'm guessing its going to need a bit of care to drill out the existing hole (size unknown at this point) and then to start the tap squarely especially with the head / engine in situ.

    If it was a more common size / pitch I'd happily spend £30 or so on a better V-coil set with the stepped tap etc but for a such weird thread size of M10 x 1, which I'll likely never use again I'm not sure it's worth it unless the overwhelming consensus says that the £7 kit above is a waste of time.
     
  2. Pete.

    Pete. Member

    Messages:
    9,408
    Location:
    Kent, UK
    That is a very common spark plug thread, one of the most common ones for bikes, used for any NGK plug starting with the letter C.
     
  3. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    So I've read a few times now guessing that must be for small 4 stroke road bikes? here's the odd thing I've ridden 2 stroke off road bikes from PW50 to CR80, RM100, CR250 & SX250 and a few others in between over the last 25 years or so and played with countless small 2 stroke and 4 stroke engines along the way and this 10mm plug was the first I've ever seen :o
     
  4. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    10,429
    Location:
    CX Derbyshire
    I know someone who has used those and he says they are better than helicoils. Keeping the hole square is the part he says is essential.
     
  5. Pete.

    Pete. Member

    Messages:
    9,408
    Location:
    Kent, UK
    Nope, most superbikes. My turbocharged Hayabusa included.
     
  6. angellonewolf

    angellonewolf Member

    Messages:
    5,332
    Location:
    bristol england
    actual no its not that bad i had a lawn mower that i had striped the thread on took the head off drilled round the hole to enlarge it slightly so its bites near stright away and turn oil back and forth and it went well think i might have posted a quick review on this site dont know if any one can find it ?

    i think i paid 4.99 for my set and still got it never used it twice but got me out of a big hole and think i did say i would never use it on a car but for smaller engines mowers and such there a good passable and good for the price
     
    slim_boy_fat likes this.
  7. winchman

    winchman Member

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    3,565
    Location:
    Merseyside
    Many years ago I sold tools for a living I sold loads of these and never had a complaint, just lock tight the repair thingy in to the head and its as good as new
     
    slim_boy_fat likes this.
  8. colnerov

    colnerov Member

    Messages:
    3,495
    Location:
    Nr Gatwick UK
    Hi, The first and only time I've come across that type of insert was when I bought a Rover P6b to sell on. I gave it a service and when I took the plugs out the insert came out with one, I couldn't get it off the old plug so I just cleaned the plug up and put it back. The car sold before the plug gave any trouble so I never had to deal with it. So I don't know how it locks in the head as opposed to the plug. I offer this tale for what its worth.

    Colin
     
  9. angellonewolf

    angellonewolf Member

    Messages:
    5,332
    Location:
    bristol england
    on the set i had there was a punch with it once you screwed it in you give a a few sharp taps to bend the edge over thats supposed to lock it in but as above it did put it in with thread lock
     
  10. Jim Davey

    Jim Davey R H Davey Welding Supplies Ltd

    Messages:
    5,432
    Location:
    Southampton
    Thread lock on the insert and copper grease on the spark plug. They've always come out trouble free for me. I use the Snap-On one piece steel inserts with a flange on the top. Used to put them in the Kart engines right from the start as we were forever taking the plugs in and out to check mixtures.
     
    atomant48 likes this.
  11. johnser

    johnser Member

    Messages:
    2,021
    Location:
    North Cornwall
    Zero cost, "worth a go", repair; pull off the squish ring and put the plug back in with loctite. You will grab a fresh thread and it might seal ok and might not pop out.

    I drove many thousands of miles like this on a car once. Mind you, I doubt it had a great deal of compression!

    You could try similar with a longer reaching plug but unless you're lucky, it'll foul the piston. Either way, nothing to loose, apart from perhaps your eye if you stand over it while it's running!
     
  12. Kayos

    Kayos Member

    Messages:
    5,662
    Location:
    Yorkshire
    I used one of those to repair a mini, the new ones, seller didn't look impressed when we drove it off after fixing on the road by his house
     
    Last edited: Jun 25, 2017
    colnerov likes this.
  13. atomant48

    atomant48 Forum Supporter

    Messages:
    906
    Location:
    Salisbury, UK
    Are you going to take the head off first (I'm assuming it's a 2 stroke)?
     
  14. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    It's a 49cc 4 stroke cheapanese engine. Not made my mind up about taking the head off.... Certainly would be best practice but there just enough room to do it in situ and as I'll likely get little more than a thank you for doing it I really don't want to spend much time on it tbh and if I can get away with doing it in place then great.

    I'll get one of them cheap repair kits ordered up and by the time its arrived hopefully I'll have decided which way to go.
     
  15. angellonewolf

    angellonewolf Member

    Messages:
    5,332
    Location:
    bristol england
    Would have thought on a that type of engine depending on what size of engine it is

    If small 50cc or such there will prob not be that much clearance between the head and when you put the tap in they do go quite far in
     
  16. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    Decided this evening to get the head off. Watched a few youtube videos of the Lifan pit bike engines (which this appears to be or at least is a cheaper copy of) 6 nuts and 8 bolts in all so about as easy as it gets.

    [​IMG]

    It'll definitely make tapping the new thread and fitting the insert easier.
    [​IMG]

    You can just about make out that there are about 4 decent threads right at the bottom the rest are completely gone:
    [​IMG]

    The repair kit and threadlock should be here Wednesday or Thursday I'll update the thread then on how it goes...
     
    Last edited: Jul 2, 2017
    galooph likes this.
  17. angellonewolf

    angellonewolf Member

    Messages:
    5,332
    Location:
    bristol england
    good luck
     
  18. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    The thread repair kit turned out to be a complete success. I'll get a photo of the repair on the weekend but just to prove that the £7 kits work....


    Don't think it was ever designed to move a 15 stone lump (not me by the way) but did surprisingly well.
     
    galooph likes this.
  19. steveo3002 Member

    Messages:
    5,431
    cambridge uk
    the picture looks like its top hat shaped...does the plug now sit higher than before or what?
     
  20. Paul99

    Paul99 Member

    Messages:
    606
    Mid Wales
    Yes the insert is a top hat shape. The plug would sit higher but only by the thickness of the rim (1mm in this case).
     
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