Rump Rump Rump goes the chain

Discussion in 'General Questions' started by Bill Snow, Apr 19, 2007.

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  1. Bill Snow

    Bill Snow Guest

    After putting this motor (Chinese 70cc ) on the bike it worked great. But after a few miles it developed a rump rump rump sound in the chain area. It was not rubbing on anything and the sound is very pronounced.

    So, here is what I have done:

    Replaced the chain with a heavy duty chain ( thought the light chain may have become stretched ).

    Rechecked the rear sprocket to be sure it is well centered. It is. When I bought the kit from Livefast motors I got both the small and large sprockets. Chose to use the large sprocket with 9 mounting holes, the smaller sprocket only had 4 mounting holes.

    Checked the chain run ( that it is running straight from sprocket to sprocker).

    I still get the rump rump sound and the chain does not seem to be running smooth but it does not tighten and loosen as it turns that I can tell. ??????

    Decided to stop here before I start changing sprockets and other things, maybe get some suggestions before I dug in any further. I noticed there are some pretty sharp people on this forum that are better at this than I.

    Bill Snow

  2. Guest

    Guest Guest

    Positive it's the chain?
  3. gone_fishin

    gone_fishin Guest

    take the clutch-arm cover off...plug out, roll the the chain seating all the way down on the drive sprocket?

    if not, you'll have to grind or file a bevel on the teeth.
  4. azbill

    azbill Active Member

    it's also possible that your new chain doesn't fit the drive sprocket
    I had to use a livefast sprocket on my howell engine so I could run a heavy-duty bmx chain so you might have the opposite dilema
  5. Bill Snow

    Bill Snow Guest

    No, I don't think it is the chain itself but the noise is coming from that area.

    Thank you for the tips, I'll check it out closer next week.
  6. Thejman

    Thejman Guest

    intake gasket, I know it sounds weird but I had the samething happen. is this what happens when you try to gain speed-full throttle? Beacuse I got noise from the engine bogging down going rump rump beacuse it was not getting enough gas/air was seeping in from the intake. That same problem cost me 2 chains at 15$ and a brand new back rim for $49 because it was bent or so I thought that was the noise. :x if only I knew it was a piece of gasket material and sealant a total of $10 that would get rid of it.
  7. gone_fishin

    gone_fishin Guest

    another thought (ow!)...

    my chain-tensioner had a tendancy to NOT turn if i had it too tight, the chain would grind away on it & it made a pretty bad noise.
  8. 1cc

    1cc Guest

    Yep the problem is you do not have enough slack in your chain, & the idle roller is causing the noise. Loosen your chain so you have about 3/4" deflection on the bottom of chain. A little chain lube also helps.
  9. Bill Snow

    Bill Snow Guest

    OK, I'm still watching and taking it all in. Thank you for responding, I appreciate the help.
  10. gone_fishin

    gone_fishin Guest


    but is it helping? any progress?
  11. Bill Snow

    Bill Snow Guest

    No more rump rump. I used the information presented on this frorum to do a closer check and make some changes.

    1. I did the same thing, chain tensioner too tight and not turning. Corrected.

    2. Made sure chain is correct and fitting well into both sprockets. The fit is good

    3. I again checked the intake gasket as suggested. When I installed the engine the gasket supplied was too thin to seal good so I had made a new one and it is still sealingl.

    4. I did fine the rear sprocket was not centered as well as I thought it was. I recentered it and almost on the button, but still do not think it is perfect. I did as suggested and made sure the chain is not too tight. I received two rear sprockets from the dealer and used the larger one because of the hills around here. I was surprised at the power this little engine has, so later I think I'll change to the smaller sprocket and see if I can do a better job on centering it.

    In spite of not having the sprocket centered perfect it is doing very good. After making the above changes the drive sounds just fine and runs smooth.

    Well, by now you probably know I appreciate the help.

    Thanks and Best Regards

    Bill Snow
  12. Thejman

    Thejman Guest

    good to hear the update :) My back rear sproket is not to center either but it's tight has not effected the bike maybe some speed lose but I can live with it for now.