stupid threaded rods

Discussion in 'Motorized Bicycle General Discussion' started by kyl 46&2, May 24, 2010.

  1. kyl 46&2

    kyl 46&2 New Member

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    i keep breaking these things like no tomorrow. third time in the last five days only this time it went back into my tire and shredded it. now its gonna cost me 90.00+ to replace the tire and tube. is there a better way to fix this? i was thinkin about tryin stainless steal. its strong and won't rust but not sure weather thats the real problem.
     
  2. Cabinfever1977

    Cabinfever1977 New Member

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    What threaded rods? the rear engine mount studs? and a new tire and tube is like $26 not $90, $90 you could get a whole new bike, unless you have a special wide tire.
    Did they unthread thereself and vibrate out? you could try loctite on them and double nut studs.
    Maybe they weren't all the way in and maybe were loose in the first place.
    A rear fender would stop the threads from going into the rear tire,just in case.

    Or are you talking about the chain tensioner?
     
    #2 Cabinfever1977, May 25, 2010
    Last edited: May 25, 2010
  3. kyl 46&2

    kyl 46&2 New Member

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    its a 29''er the tube is not so bad $5 or so its the tire thats killin me $69 for the bloody thing. 2.1'' wide. my local bike shop doesn't carry that size on a regular basis. gotta order it myself. yeah i'm not sure whats going on with the motor mounts. i read i here some where that using rubber under the mounts was a bad idea but i'm thinkin i got some hella bad vibrations maybe its just to much metal stress and i should go back to the rubber pads. i''l give the extra nut a shot too. its just disheartning 3 times in five days. although i've gotten really good at taking the bulid down and putting it back together.
     
  4. Cabinfever1977

    Cabinfever1977 New Member

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    Use some locktite on the studs and make sure there in there good. And make sure the mounts are flat up against the frame.
     
  5. taddthewadd

    taddthewadd New Member

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    Is the threaded rod vibrating out or snapping in half? If it is vibrating out then the lock tight will work or if you buy the engine hardware kit from sick bike parts the end of the threded rod has a allen hex that you can tighten the rod with. It allows you to get it into the engine block really tight.
     
  6. kyl 46&2

    kyl 46&2 New Member

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    my rods are snapping. i think its a combination of both though. the nuts vibrating off then the loosened mount snaps the rod. i just got done reading the thread on vibrations and i think that is my main culprit. lots of great ideas. i have to order a few things so i''l have time to mull all this over and fix this problem. in the mean time i'll pull my stock build out of the basement and use that. thanks guys
     
  7. Retmachinist

    Retmachinist New Member

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    If you have broke three sets, you have got some big time vibration going on there. Don't use any kind of rubber mount, and also don't use stainless steel. It is pretty, but certainly not tough.
    I think that area is the weakest link to the engine mounting so I drill mine out and tap them 8mm right out of the box before I install the motor. Never have had a problem.
    Seems like it is only the back mount that causes the problem for alot of people.

    John
     
  8. IVIaxPow3r

    IVIaxPow3r New Member

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    I actually just had my front left mount stud snap as well - so I feel for you. I am looking to get it drilled and tapped as well - here's hoping it doesn't happen again.
     
  9. civlized

    civlized New Member

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    I concur with Ret. Stainless has a low shear strength. It breaks pretty easily. Grade #8 won't break, but something else will if there is different problem that is causing these failures.
     
  10. Maxvision

    Maxvision New Member

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    Check that the sprocket on your rear wheel is not off-center. If it is, the slacking and pulling on your chain every tire revolution will create quite a bit of strain on your engine mounts as well as unnecessary vibration. Also make sure your chain is not too loose or too tight. If your chain is too loose, engaging the clutch will give it a hard YANK.
     
  11. kyl 46&2

    kyl 46&2 New Member

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    i'm actually going to order a sprocket from kingssalesandservice tonight. i have disk break hubs that aren't being used at the moment so i figure it will be a better mount the rear sprocket. think i'll go with the drill and tap as well. breaking these rods is just getting annoying.
     
  12. taddthewadd

    taddthewadd New Member

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    What size of a sprocket are you going to order from kings sales?
     
  13. kyl 46&2

    kyl 46&2 New Member

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    40 0r 38 tooth. not sure yet. i have 29'' wheels so i want to keep a little torque on them.
     
  14. kyl 46&2

    kyl 46&2 New Member

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    i could probably get away with 36. my engine has some balls to it.
     
  15. taddthewadd

    taddthewadd New Member

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    I have a 38 from him with the top hat adapter on a 26" bike. I will PM you because there are some possible problems you might run into. Since I have gone down this path I can help you figure them out.
     
  16. 2door

    2door Moderator
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    Forget threaded rod. Replace them with Allen head cap screws. They will normally come in hardened, grade 8 steel and if your mount is contacting the frame as it is designed to do you shouldn't shear them unless you have something else going on. Check that rear sprocket installation as was suggested above and make sure the front mount is tight and snug against the frame also. Do not use rubber. It doesn't eliminate the source of the vibration, only transfers it to other parts, like fasteners. Stainless is pretty, but weak.
    Tom
     
  17. Gareth

    Gareth New Member

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    are you using the correct size rear mount for the down tube? If you use a big tube mount on a small tube frame it will snap em...
     
  18. kyl 46&2

    kyl 46&2 New Member

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    i do have the large mount on the down tube but my down tube is also large. i will take a closer look and see how its fitting. i think i may have an issue with how flush they are though. i also need to rework the chain tensioner. my chain stays are a weird shape and have givin me nothin but trouble.
     
  19. kyl 46&2

    kyl 46&2 New Member

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    just a random thought but what about small rubber washers under the metal washers for the motor mounts. think that would dampen vibrations or turn into a nightmare.
     
  20. Cabinfever1977

    Cabinfever1977 New Member

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    I wouldn't use anything under the engine mounts.
    Rubber and even tape will wear out over time and cause the mounts to loosen, and on the rear mount gas from the carb will drip onto the rear mount and anything under it, rubber or tape will get eaten alive and make a sticky mess.

    If you need to get rid of vibrations at high rpms get a smaller rear sprocket to lower rpms or keep your speed down.
     

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