Rump Rump Rump goes the chain

B

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
 


G

gone_fishin

Guest
take the clutch-arm cover off...plug out, roll the bike...is 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.
 

azbill

Active Member
Joined
Dec 15, 2006
Messages
3,697
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
 
B

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.
 
T

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. :censored: if only I knew it was a piece of gasket material and sealant a total of $10 that would get rid of it.
 
G

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.
 
1

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.
 
B

Bill Snow

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