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Stripped thread(s) on the carby

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Gluteus Maximus, Apr 23, 2012.

  1. Last year i bought a jet kit for my Honda GB500 (single). The kit came with some replacement stainless hex screws to replace the soft standard screws on the float chamber. I changed the jets (and screws) fine and the bike was running ok. This week however i decided to try a different pilot jet, but stupidly got overzealous when putting the carb back together.



    Due to over tightening, I have accidently stripped the threads in the carb body for 3 of the the 4 screws that connect the float chamber. I need to have them re-tapped/thread inserts in place to reconnect and seat the float bowl top.

    Can anyone reccommend anyone in the Sydney CBD area that is able to do this sort of small scale work?

    Thanks.
     
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  2. Inside the cbd? unlikely. I distinctly recall there is a mechanic of good repute in alexandria area.
     
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  3. Helicoils may do the job
     
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  4. I dunno. What happened to whacking in a couple of tek screws? Honestly, the youth of today :D.

    Seriously though, it might be worth trying to do the job yourself. A Helicoil or Recoil kit for such titchy sizes will cost you ~$75 and you'll have the satisfaction of having reclaimed your own components. I don't know what outlets you have in Vic but over here I'd be heading to Coventrys, Blackwoods or even Malz. From looking at my own carb, I'd say the screws will be M5 or possibly M4.
     
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  5. Haha - I was tempted for a second when it happened, self-tappers could make a good temporary fix. But carbs for the bike are so hard to find that I’ve got to preserve what i have.

    Helicoils are definitely the way, though i might be tempted to try a thread -chasing tap first. After stripping the threads initially, I’m not sure that i trust myself to be able to complete a proper Helicoil/re-tap job though.

    Other than mechanics, what sort of workshops would undertake this, would be simple job, for a skilled tradesman?
     
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  6. Thread tap may not work you've pulled the metal away so its got little to 'chase'.
    You may be able to tap it to the next size after getting new screws, cheaper than a helicoil, depends on how much meat you have around the holes.
    Now might be a good time to start looking for decent carby kit. :)
     
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  7. I had a slight epiphany the other evening when thinking about how I was going to sort the threads.

    The replacement screws that were supplied with the jet kit were actually quite short – i.e. were only engaging about or 3 threads in the carb body. This, along with my impatience and over torqueing were what caused the threads to strip. So in a last ditch attempt, I bought a pack of 15mm m4 screws and had a go at sticking these in to replace the hex screws and stripped threads. Low and behold, owing to the longer length of these screws, they were able to engage and utilise the remainder of the thread that was still intact deeper into the carb body. Fortunately for me, the 2 that stripped were on the side of the fuel chamber that had a lot more space below the hole, so that the extra length of the new screws could safely come out and not damage the carb body.

    Anyways, I’m certainly much a happier for now, though I will look at having the threads helicoiled at some stage in the near future.
     
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  8. Good one. Just be a bit careful when tightening them in future because you've now got fewer threads engaged than there should be.

    Helicoiling them when you get the chance would still be a good idea. The trouble with steel screws or plugs in alloy components is that, with removal and replacement over time, the threads will eventually wear out. That's why the engineer's method is to use a stud which screws into the soft metal and then stays put for the life of the bike, with a nut on it to give you steel on steel threads where the wear takes place. Screws into ally are an accounting decision, not an engineering one.

    A helicoil in each hole will, at least, give you steel on steel for better durability.
     
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  9. As it's on the outside of the carbie, you can buy another product that repairs threads. You mix up a putty and put some in the hole. Then you put a thread release coating on the screw and then screw it all together. The putty then sets and all is good.

    The retailers claim it's stronger than aluminum, but my experience is it's only good for low load applications.

    It might help you get a full length of thread back.
     
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