Knocking sound plz help

[reddog]

As much as I would like one of those $2500-$7500+ bikes in the bike shops I just dont have the money. Picked this up from academy for about $180

http://www.target.com/gp/detail.html/183-6840482-4942463?asin=B000KZ1GHQ

Think this is the same one pretty close. Been just over a year now, put about 1500 miles on it in and dropped another $100 in repairs, not doing to bad I guess.

Anyways, last few days it's been making this noise like.. well only way to put it into words is it sounds almost like when you push in the top of a pickle jar. That double popping sound it makes. Almost sounds like the chain is under to much pressure, but sometimes I will also hear this noise when I let up on the pedals. I have checked many times nothing is touching and it's not rubbing any place. Also I can get off the bike, raise it up and pedal it as fast as I can and it doesn't make this noise.

I'm sure someone here has heard this before and can probably pin point the problem for me. Plz do

Thanks for any advice!

[Bill]

Process of elimination I would try the seat, weird to say but sounds can come from anywhere. Take off the seat and post ride it just for a little way to see if it happens. If it still makes the sound put seat back on and push the handle bars forward and pull them back toward you. If not there press with your foot on each of the pedals with hard force. Where I am going with this is to try and locate the source of the popping.

[reddog]

I have to unsnap the seat before it will even move as it's on really tight. Same with the handle bars, I can push forward with everything I got and they don't even move. Took off the seat still have the same problem. Holding myself up by the wall I pushed down on both pedals and it made no sound or shifting sounds.

Only one thing I found out new, and that's when I shift my main force to the left side it doesn't make this noise. Most the time when I ride, by habit I distribute more power from my right side then I do my left. Maybe this has thrown something off balance.

Thanks for the help and fast reply. If you have any more ideas plz let me hear them. Thanks.

[Joe_W]

Check and see, if the cranks are not completely fixed. If the bottom bracket has a tapered square axle, then a crank that can move slightly might produce this sound, two knocks per turn, always at the more or less same position of the cranks. Or the bottom bracket might be worn...

I think DaveM wrote (a while ago) that "mystery noises" were really difficult to solve..

[DaveM]

"Mystery noises" are tough, but it's also tough to describe a noise with words. Loose cranks usually "creak" rather than "pop". But who knows. My first guess would be a bad bearing. Try slipping the chain off the chainrings to the inside so you can spin the cranks freely. If that isn't smooth, probably a bad bearing. Try taking the wheels off and spin the axles by hand to check them. Could be lots of other things too though. Check to make sure your stem is greased and tight. (BTW, your handle bars and seat should not move without loosening the bolt. Otherwise they could move while you're riding which is dangerous.)

Try a few things and report back...

[reddog]

I ride for fun, well it's more or less my workout as it's about all I get being a computer tech. I did what dave said because I could better understand it. Took off the chain and cropped myself up and it was still making the noise. I don't have the tools to fix that so I called the bike shop and told him where the noise was coming from and he started calling off the all the symptoms before I could get another word out. Told him yea, that nails it on the head, he said one of the cranks were lose. $22 after tax, I'm just glad it's fixed and as much as I can't afford to even part with that much I'm just glad it wasn't something that cost more.

Thank you both for your help!