When turning agitator on it gets jammed in the spur gear.

Proper cleaning requires the spur gears be removed taking care to not lose the small dowel pin (dog). The spur gear needs to spin freely on the shaft. If not, clean the shaft with fine emery cloth and the inside hub of the spur gear. Clean dirt from the ratchet side of the spur gear so the dog can engage and release properly.

The dogs need to move in and out freely so as to engage by gravity. Clean any rust and dirt from the pin and pin hole.

Gears having cylindrical pitch surfaces are called cylindrical gears. Spur gears belong to the parallel shaft gear group and are cylindrical gears with a tooth line which is straight and parallel to the shaft. Spur gears are the most widely used gears that can achieve high accuracy with relatively easy production processes. They have the characteristic of having no load in the axial direction (thrust load). The larger of the meshing pair is called the gear and smaller is called the pinion.

contact the manufacturer spares for the gear or a service agent for the make
spur gears are available from most bearing retailers
all you need is a sample
there are spur gears and cogs available from e-bay

Your set up is most probably: an electric motor turns a worm gear that turns a large spur gear that turns a smaller spur gear that rides on a rack gear. The smaller spur gear (pinion) that rides the rack (yes, as in rack-n-pinion), allowing the up-and-down travel of the massage balls, has broken teeth which may not be visible because it's hidden under the larger spur gear. They are all plastic gears with lots of white grease.

An electric motor turns a worm gear that turns a large spur gear that turns a smaller spur gear that rides on a rack gear. The smaller spur gear (pinion) that rides the rack (yes, as in rack-n-pinion), allowing the up-and-down travel of the massage balls, has broken teeth which may not be visible because it's hidden under the larger spur gear.

Youre not setting the right gap between spur gear and clutch bell. all the adjustment is on the engine side so once you got youre spur gear in place loosly fit the engine. Push the engine close to the spur gear so the teeth interlock. Cut a long thin piece of paper and feed it throgh the teeth.turn the clutch bell around. It should feel the same all the way through the turn. If not push the engine closer if it starts feeling loose or ease it away if it starts feeling tight. the paper should come out the other end with a step pattern. the reason for the paper and turning the clutch bell is even though the teeth are intwined at first, once you turn say 3 quaters of a turn if the engine and transmission is not parallel it can move 3 to 5mm in either direction. Lastly use thread lock on all bolts as the vibration can move these and hey presto you are getting another one. Hope this helps.

When the engine is started the pisten goes up and down which in turn turns the engine shaft which then spins the clutch shoes around to a point where force pushes them out to touch clutch bell, clutch bell then spins spur gear. in order for spur gear to turn the clutch bell would have to turn to. If this is happening check the dog bones that go into transmission are all ok. Lift car of of ground and spin rear wheels to see if front wheels turn and spur gear.

clutch bell and spur gear are not aligned and 100% paralal. When youre near fitting spur gear put a piece of paper through teeth. Should feel same through the complete turn. Also use thread lock on all bolts. Hope this helps.

Replace the spur gear !!!!

it seems to me the you have either a clutch problem or a spur gear problem.if it is the clutch the clutch drum will be blue.witch means you need to replace the clutch and drum.if it is a spur gear problem you need a new spur gear.to check it out,take the chain and bar off the saw.now look at where the chain rides in the gear.there should be no markings on the gear.if the spur gear has any dents on the gear then the gear is bad.if you are getting denting on the surface then you are over tighting the chain.this causes the chain drivers to ware also.most likely this is your problem.hope this helps,let me know if you have any more questions............