Chain Tensioner luck with no tensioner?

Discussion in 'Transmission / Drivetrain' started by 2strokepoke, Sep 7, 2011.

  1. 2strokepoke

    2strokepoke Member

    i've been having trouble with my tensioner. i used the original one for a few hours and it finally came loose so i tightened it and stripped it so i rebuilt the idler and put a new bolt threw it and stripped that one.. so i've been thinking of just making the chain shorter and running with out. my bike is a 20''.

    anyone have luck with not running a chain tensioner?

  2. motorpsycho

    motorpsycho Active Member

    yeah i ran my 20" bike without a chain tensioner for about a year.
    the problem is that sometimes the chain will go loose, tight, loose as it rotates.
    if you don't get the chain tension adjusted just right without a tensioner, the chain can be either too loose when it gets to the "loose" stage of it's rotation, or too tight when it gets to the "tight" stage of it's rotation.
    the chain needs to be neither too loose or too tight in it's full rotation so it doesn;t come off, or break.
    it can be done but it takes a few tries to get the chain adjusted to the right tightness.
    you will probably also find out that you won't be able to get the pedal chain adjusted and the engine chain adjusted so that they are both right. one may be too loose, while the other may be too tight.
    This can be a challenge in itself, and sometimes you have to use a 1/2 link in one of the chains to get them both adjusted right.
    this is where the tensioner really helps because it takes up the extra slack in the engine chain, while allowing the pedal chain to stay tight.
    Last edited: Sep 7, 2011
  3. Jay

    Jay New Member

    i didn't try it but i saw somebody did . i think it's no problem your bike is 20" but make sure you the chain is in line from gear to sprocket . The chain tensioner help keep in line someway.
  4. motorpsycho

    motorpsycho Active Member

    no, the tensioner has nothing to do with keeping the chain in line.
    what keeps the chain in line is how the rear sprocket is mounted to the rim. the chain must run in a straight line frm the engine sprocket to the rear sprocket when looking at the bike from behind and it can do this without a tensioner.
    the chain tensioner does just what it's name keeps tension on the chain to help keep it at the right tightness.
  5. 2strokepoke

    2strokepoke Member

    i guess that answers my question. i'm just not sure if i wanna make my chain shorter cause theres not going back with the way i shorten chains.. im too cheap to get a decent puller. i dont wanna make it short and then it still be too loose.. I spose i could get a half link
  6. Jay

    Jay New Member

    Yes ,you are right . I didn't explain it well. I meant the tensioner help keep chain in line without dropping . I'm using a new type tensiner I want to show you guys but don't know how to post a picture.
  7. 2strokepoke

    2strokepoke Member

    well my problem i think is that the idler wont spin and its putting stress on the brackets and making it pull towards the tire and taking the chain with it... i cant tighten the bolts anymore and welding is not an option. if i try to loosen the idler it just slides down then tighten it at all and it locks up
  8. motorpsycho

    motorpsycho Active Member

    the stock tensioners are garbage.
    your best bet is to make your own, or buy a good aftermarket one(but they are expensive).
    you can run without a tensioner, but it's harder to get the chain tension just right.
  9. 2strokepoke

    2strokepoke Member

    im thinking of upgrading the bolts to a larger diameter so it will tighten better. havent figured out what to do for the idler/roller itself. possibly making it spring loaded.
  10. FunkBike

    FunkBike New Member

    Sprocket alignment

    i'm just a noob, but i think that this is (maybe) because your rear sprocket is not perfectly aligned. these chinease sprockets are not the best when it comes to alignment.
  11. Jay

    Jay New Member

    See this tensioner . Tell me you guys idea.

    Attached Files:

  12. BoltsMissing

    BoltsMissing Active Member

    From actual experience, I have a spring chain tensioner on one bike frame, but does not work well on another frame.

    There are points to consider, mainly geometry and swivel, having a bolt with a washer defeats the purpose even when you get the geometry right.

    What geometry?
    The downward push on the chain when you let out the clutch, the swivel needs to bottom out, sort of like a pendulum, when it's rock bottom and the engine fires, it retains the tension.
    It's not the spring tension that holds the compression, it's the correct angle of the swivel action at that maxed out point, at TDC.

    Dream ride when it's right.

    That pic. shows the right idea for home made, it's all in tweaking the geometry through trial and error.

    I would use a better quality chain because the china chain stretches over time and messes up, confuses things, "false positive" and all that when trying to fine tune the angle.

    What you have there is right though, except have some sort of adjustment for the spring tension. If it's too tight ya lose power, too lose it falls off.

    The swivel part, not cheap, but a flat needle roller thrust "washer type" bearing kit, ( for those of us who don't have a lathe ).
    It comes in 3 parts, the flat needle roller bearing and the 2 bearing washers for either side.
    Initially it will constantly need adjustment till the bearing "beds in", as close to as zero tolerance as possible. Too lose and it swivels side to side, too tight and it won't work freely enough.

    I used a wire ( coat hanger) to lengthen or shorten the spring tension between the fixed part, but above the brake with a special rubber lined wall mounting clip electricians use around small diameter tubes.

    It's worth effort when it's all done though.

    Warning: Once you have ridden a MB with a corrected spring tensioner on a china engine, it's addictive.
    Last edited: Sep 18, 2011
  13. happycheapskate

    happycheapskate Active Member

    My experience was that with no tensioner, the bike vibrated like crazy! Running a smaller cog (36 tooth) seemed to help, but maybe just because it is truer (milled out to fit on hub) I've heard that running the fat heavy chain helps because you can run it looser and it won't derail. I didn't like the stock chain. I use a neoprene roller that acts as a vibration dampener. The chain is snug but not overly tight. See my pics or pm if you need help. It mounts on the happytime case.

    What kind of BMX fits a happytime, or do you have another kind of engine?