Chain doesn't move

There is a clutch behind the metal housing where the chain sprocket at the engine end attaches to the chain . There are wear parts with springs on them that have to be changed. ChainSaw Shed Chain Saw Parts for Wen Wagner Brand Chain Saws Chains Bars... You can get parts here.

This could be a few things:
1) Your clutch plates may have worn out so that even when the bike is in gear, it will just rev, but no power will be transmitted to the drive shaft (smaller front chain sprocket is the driving gear, larger rear sprocket on the back wheel is the driven gear)
2) The front chain drive sprocket has come off under the cover on the motor - if the chain is really slack, have a look.
3) The front chain drive sprocket SHAFT has sheared. (basically, meaning that the shaft has broken into two parts as it couldn't handle the drive power (torque) being delivered through it to the chain drive) With the motor on, listen for grinding noises internally
when you rev, from the vicinity of the front chain drive cover. If its rough and grindy, the shaft may be sheared. Then with the motor off, take the cover off and leverage the small chain drive sprocket away from the motor with a screwdriver, and see if the shaft can just be pulled out of its sealed opening. Unfortunately with these bikes, the metals used in drive shafts and motors are not always heat-treated or hardened to the standard they should be, so shearing and premature failure can happen.
4) The gearbox or something in it has blown, unfortunately for the same reason above, quality related.
Its fair to say that these great little bikes are here for a good time, but not for a long time.

Probably the shaft on the sprocket has sheared off.

Knox Knolls Outdoor Power Equipment
Springfield, IL 62704
www.knoxknollsope.com

Hi, poppa530 I will try to help you out. You probably installed the chain so it is not engaging the sprocket. Remove the chain and re-install, but make sure it is engaged on the sprocket located behind the drum where the shoes are that as the RPM goes up engage the drum and turn the chain. I can't think of anything else that could be causing this problem, unless the drum and clutch shoes are not engaging any more. Do you know if the clutch shoes, drum and sprocket have been removed from the crankshaft, and maybe not re-installed properly? Can you turn the chain by hand? If not, something has jammed preventing chain from turning. Have you recently installed a new chain, bar or both? If so, you might not have the right width drive link tang or the right pitch on the chain. If a new bar has been installed the bar groove might not be the right size. You might also check out the sprocket to see if it is bent or damaged. I hope I have helped even a little bit. All the best and good luck. Any questions welcome.

It is possible that the clutch sprocket teeth are badly worn causing extra wear on the drive teeth of the chain. Remove the bar and chain to check the sprocket--you can determine the wear by comparing the area where the chain runs to the edges of the sprocket that are relatively unworn. If the sprocket requires replacement, the chain should be replaced as well. The chain normally should be loose enough that the chain can be moved by hand, but it should not droop from the lower bar edge. Check the chain oiling by running the bar tip at speed near some cardboard--it should throw off a thin line of oil after a moment or two. There should be an oil volume adjustment screw located on the under side of the case near the chain return area--turn CCW to increase flow. Hope this helps!

Does the sprocket drive shaft turn when the sprocket does not? If so, look for broken coupling between the shaft and the sprocket. If the output shaft doesn't turn, then suspect a damaged (probably plastic) gear within the gearbox. Hope this helps!

Check the chain drive sprocket to see if it moves when the motor runs. If not, there may be a sheared key between the shaft and sprocket or the teeth on the sprocket are badly worn off. Hope this helps!

so when you put it in gear it doesnt move with clutch disengaged???

Does the motor continue to run when chain stops? Electric saws usually don't have a clutch, so I would look for badly-worn chain sprocket, or a possible sheared key in the sprocket hub, or a loose mounting nut. Remove the chain and bar, try to turn the sprocket by hand (wear good gloves). There may be some type of overload clutch built into the sprocket.

have you greased your clutch bearing ever.some times they get dirty and tighten up after running a while.pull your clutch off and clean and grease bearing with a little alex grease,and I mean just a few drops.not meant to have a lot of it,too much will burn the crank shaft and you will have more problems then you started with