Engine Trouble CHUNKY drive and INCONSISTANT chain tension

Discussion in '2-Stroke Engines' started by hairytoes, Jul 30, 2015.

  1. hairytoes

    hairytoes New Member

    Hi! i have an 60cc/80cc 2 stroke engine from gasbike.com that i have just installed onto my bike. The drive shaft does not spin freely and is very chunky while spinning the 10 tooth driver. Also, the sprocket is nearly perfectly indicated on the rear wheel, yet the chain tension is very inconsistant, ranging from tight to very slack. Feeling really frustrated :helpsmilie:

  2. crassius

    crassius Well-Known Member

    new chains will stretch a lot & fit better after 10 or 15 miles

    are you sure rear sprocket is true in BOTH left/right wobble AND up/down centering?

    about 1/16in off in centering will cause 1/2in or more in loose/tight
  3. hairytoes

    hairytoes New Member

    Wow! Didn't realize that little of variation would cause that. I can fiddle with that, however i'm more concerned with the chunkyness of the drive. I would take it apart and see whats going on, but the driver doesn't allow a socket to fit onto the nut holding it on.
  4. crassius

    crassius Well-Known Member

    sometimes with a 415H chain the rollers are too large to fit down nicely on a drive sprocket that was stamped with wide, flat topped teeth (other factories use pointier teeth) - in that case, a bit of filing or grinding to make the teeth pointier will help

    over time, as the chain stretches, it will fit better, but I like to 'adjust' those teeth first - an allem wrench stuck into a chain link will hold the sprocket from turning while you remove it with a 19mm socket, and then use the kit's puller tool to get it off the shaft
  5. butterbean

    butterbean Well-Known Member

    How can a drive shaft be "chunky" while spinning? I really don't get your description.
  6. hairytoes

    hairytoes New Member

    upon taking the nut off with an allen (thanks for the tip!) my dad pointed out that the key holding the sprocket in place was rubbing against the bearing. this along with the overtightness (i create my own words :cool2:) seems to be the culprit. hes grinding the key down just a hair so it sits properly and ill post again shortly to see if that solves the funky chunky monkey problem!
  7. hairytoes

    hairytoes New Member

    upon taking the nut off with an allen (thanks for the tip!) my dad pointed out that the key holding the sprocket in place was rubbing against the bearing. this was the culprit! He grinded the key down just a hair so it sits properly off of the bearing and that solved the funky chunky monkey problem!

    Another question, with the flower nut tightened, is the driver supposed to be able to move without the clutch pulled? How tight should the flower nut be? my father explained that it should not be able to move without the clutch pulled otherwise the motor would not function properly. However, in several videos ive seen guys rotate the drive without the clutch pulled. What my dad said makes sense to me but im confused because of the contradictions in the videos.
    ive done some searching on the site and couldnt find anything helpful
  8. V 35

    V 35 Member

    The flower nut is a pain, trial and error. I use welder paint markers to mark flower nut screw position . keep a magnet handy, dont lose the screw Clutch cables stretch badly . I turn barrel nuts all the way in, than 2 turns out before removing clutch cable slack .

    This way, you can tighten Clutch cable by loosening barrel nuts after break in stretching is over [ 2 tanks of gas ? ]
  9. crassius

    crassius Well-Known Member

    look on the forum for full steps to adjust cable & clutch

    what you're seeing in vids are folks that have the 'lock' button set on the clutch lever
  10. HeadSmess

    HeadSmess Well-Known Member

    ka CHUNK ka CHUNK ka CHUNK....

    thats how they be "chunky".
    cheap chains are crud. dispose of and replace with HD bmx chain or something similar...

    as crassius said...check the rollers engage the sprocket nicely.

    make sure the chain isnt so wide its grinding on the engine case or cover.

    tension at the tightest point.

    a new chain should be perfect, they start getting rough after about 10,000 km in my case...

    make sure that rear sprocket is dead concentric. yep, barely 1mm makes for 3.1 mm on the circumference, remember.

    side to side wobble, while minimizing it is good, it can tolerate some slop... depends on chain width really.

    no point running wide chains on narrow sprockets as the chain "tilts", makes point contact only, wears out fast...
  11. hairytoes

    hairytoes New Member

    along with the woodruff key issue, the chain was rubbing on the case! :dunce: chunkyness gagaga-gone after sanding the bottom of the case a little