Kx 250 rear caliper has lots of play in it i think theres a rubber or a spacer missing but i dont know what its called so i can order it

With the larger outside diameter on the outboard side hold the external spacer between the belt sprocket and the rear swingarm and then slide the axle through left side of the swingarm, the external spacer and the belt sprocket into wheel hub and then when the axle emerges from the hub on the brake disc side of the wheel, push the axle through the short external spacer, the brake caliper bracket and the right side of the rear swingarm.

I was thinking wheel bearing but you state they were replaced, are they tight in the hub? if your spokes are tight, your hub would be tight and if wheel bearing are tight everything would be correct when the axle is tightened. Your swing arm is tight as well not loose in the bearing.

There should be a allen key plug to take out of the caliper then once this is out there will be another allen key head behind the plug to undo (this is the pin) just undo, take out and the pads should be able to be removed.
Pay close attention to the direction pads come out and any spacers between the pads and brake piston as you want them all back in exactly the same with the new pads they stop the pads from rattling around when riding
good luck regards Jamie

Sounds like you've got it together correctly. There is no washer between the brake caliper bracket and the swingarm. You can put the axle in from either direction. We usually put them in from the left side so that we no longer have to remove a muffler to remove the rear wheel. The nut is now on that side. Just make sure the wheel turns smoothly and the brakes work correctly before taking in out on the road. If you hear a chirping noise when you shift gears, your rear belt is too loose.

Good luck
Steve

Remove the saddlebag on the right (throttle or rear brake pedal) side of the bike.I recommend doing it now because the bike is more stable on the sidestand; you will have to exercise considerable caution once it's on a lift, or the rear tire is otherwise elevated. There are two different length screws (three shorter, one long), a spacer, a variety of stand-offs, and a variety of rubber isolators and washers. Remove the parts (two mounts in the floor, two in the back toward the frame) but KEEP TRACK of where the parts come from, and in what order you remove them. (You're gonna hear this a lot, but replacing a part lost or misplaced prior to reassembly, or having to dismantle and reassemble the bike because things don't fit right is a LOT more aggravating).

The rear caliper and brake disk are now exposed. Remove the two hex head bolts holding the caliper to the caliper arm, lift the caliper off the disk, and gently lay the caliper outside the arm. If you've already changed the hoses to the stainless-steel reinforced type, you needn't be too careful; if you're using the hoses the bike came with, take exceptional care not to nick or cut the hose. Examine the axle on that side of the bike, CAREFULLY AND COMPLETELY noting the location of spacers and washers; when it's reassembled, you'll have to duplicate what you're looking at right now.

Prior to lifting the bike, loosen (but do not remove) the self-locking nut on the opposite side of the wheel (on the outside of the final drive unit) and the pinch nut at the end of the swingarm on the caliper side. Now, lift the bike, making sure the rear wheel is suspended and unobstructed to both the right and rear. Remove the nut from the side of the final drive and extract the axle shaft. It doesn't want to move? You're left with two choices - grasp the end of the axle shaft outside the swingarm with a pair of Channelocks or some other toothed, clamping device, and twist until it loosens and comes out - OR - remove the other saddlebag and use a 3/8 extension or extensions to tap the axleshaft through. I do not recommend the Channelocks - the scoring of the axleshaft is permanent and UGLY; if you think it looks bad after the shaft is out, wait until the RUST sets in...

With the axleshaft out, the wheel is probably hanging askew between the swingarm and the final drive unit, and there's an assortment of spacers and washers lying on the ground (you DO remember where they were a minute ago, don't you?). Place the loose bits out of harms' way, GENTLY move the wheel toward the swingarm, and it should drop to the ground, and roll out beneath the fender. BE CAREFUL NOT TO LET DEBRIS GET ONTO THE EXPOSED DRIVE SPLINE ON THE FINAL DRIVE, THE MATING SPLINES IN THE WHEEL, OR INTO THE BEARINGS. Those areas are really, really, really difficult to adequately clean after they've been contaminated.

Reassemble in the reverse order, torque specifications for the axle nut - 110 ft.-lbs. (150 nm), for the pinch nut on the swing arm - 17 ft.-lbs (23 nm). Bolts for the caliper should be torqued to 30 ft.-lbs. (40 nm).

It's a good idea to lubricate the drive splines in the rear wheel and the mating shaft in the final drive while the rear wheel is out.

reed valves are in the intake rubber manifold, so the fuel mix can only go one way into the motor, Power valves are on the exhaust side of the motor and vary the exhaust porting to suit engine revs. They are not the same

the steel brake hose and a rubber brake hose,,
the braks dont work very well with out them fitted

This is a surprisingly simple job, even easier if you have a lift. Remove the saddlebag on the right (throttle or rear brake pedal) side of the bike.I recommend doing it now because the bike is more stable on the sidestand; you will have to exercise considerable caution once it's on a lift, or the rear tire is otherwise elevated. There are two different length screws (three shorter, one long), a spacer, a variety of stand-offs, and a variety of rubber isolators and washers. Remove the parts (two mounts in the floor, two in the back toward the frame) but KEEP TRACK of where the parts come from, and in what order you remove them. (You're gonna hear this a lot, but replacing a part lost or misplaced prior to reassembly, or having to dismantle and reassemble the bike because things don't fit right is a LOT more aggravating).

The rear caliper and brake disk are now exposed. Remove the two hex head bolts holding the caliper to the caliper arm, lift the caliper off the disk, and gently lay the caliper outside the arm. If you've already changed the hoses to the stainless-steel reinforced type, you needn't be too careful; if you're using the hoses the bike came with, take exceptional care not to nick or cut the hose. Examine the axle on that side of the bike, CAREFULLY AND COMPLETELY noting the location of spacers and washers; when it's reassembled, you'll have to duplicate what you're looking at right now.

Prior to lifting the bike, loosen (but do not remove) the self-locking nut on the opposite side of the wheel (on the outside of the final drive unit) and the pinch nut at the end of the swingarm on the caliper side. Now, lift the bike, making sure the rear wheel is suspended and unobstructed to both the right and rear. Remove the nut from the side of the final drive and extract the axle shaft. It doesn't want to move? You're left with two choices - grasp the end of the axle shaft outside the swingarm with a pair of Channelocks or some other toothed, clamping device, and twist until it loosens and comes out - OR - remove the other saddlebag and use a 3/8 extension or extensions to tap the axleshaft through. I do not recommend the Channelocks - the scoring of the axleshaft is permanent and UGLY; if you think it looks bad after the shaft is out, wait until the RUST sets in...

With the axleshaft out, the wheel is probably hanging askew between the swingarm and the final drive unit, and there's an assortment of spacers and washers lying on the ground. Move the loose bits out of harms' way, GENTLY move the wheel toward the swingarm, and it should drop to the ground, and roll out beneath the fender. BE CAREFUL NOT TO LET DEBRIS GET ONTO THE EXPOSED DRIVE SPLINE ON THE FINAL DRIVE, THE MATING SPLINES IN THE WHEEL, OR INTO THE BEARINGS. Those areas are really, really, really difficult to adequately clean after they've been contaminated.

Reassemble in the reverse order, torque specifications for the axle nut - 110 ft.-lbs. (150 nm), for the pinch nut on the swing arm - 17 ft.-lbs (23 nm). Bolts for the caliper should be torqued to 30 ft.-lbs. (40 nm).

It's a good idea to lubricate the drive splines in the rear wheel and the mating shaft in the final drive while the rear wheel is out.

This is a surprisingly simple job, even easier if you have a lift. Remove the saddlebag on the right (throttle or rear brake pedal) side of the bike.I recommend doing it now because the bike is more stable on the sidestand; you will have to exercise considerable caution once it's on a lift, or the rear tire is otherwise elevated. There are two different length screws (three shorter, one long), a spacer, a variety of stand-offs, and a variety of rubber isolators and washers. Remove the parts (two mounts in the floor, two in the back toward the frame) but KEEP TRACK of where the parts come from, and in what order you remove them. (You're gonna hear this a lot, but replacing a part lost or misplaced prior to reassembly, or having to dismantle and reassemble the bike because things don't fit right is a LOT more aggravating).

The rear caliper and brake disk are now exposed. Remove the two hex head bolts holding the caliper to the caliper arm, lift the caliper off the disk, and gently lay the caliper outside the arm. If you've already changed the hoses to the stainless-steel reinforced type, you needn't be too careful; if you're using the hoses the bike came with, take exceptional care not to nick or cut the hose. Examine the axle on that side of the bike, CAREFULLY AND COMPLETELY noting the location of spacers and washers; when it's reassembled, you'll have to duplicate what you're looking at right now.

Prior to lifting the bike, loosen (but do not remove) the self-locking nut on the opposite side of the wheel (on the outside of the final drive unit) and the pinch nut at the end of the swingarm on the caliper side. Now, lift the bike, making sure the rear wheel is suspended and unobstructed to both the right and rear. Remove the nut from the side of the final drive and extract the axle shaft. It doesn't want to move? You're left with two choices - grasp the end of the axle shaft outside the swingarm with a pair of Channelocks or some other toothed, clamping device, and twist until it loosens and comes out - OR - remove the other saddlebag and use a 3/8 extension or extensions to tap the axleshaft through. I do not recommend the Channelocks - the scoring of the axleshaft is permanent and UGLY; if you think it looks bad after the shaft is out, wait until the RUST sets in...

With the axleshaft out, the wheel is probably hanging askew between the swingarm and the final drive unit, and there's an assortment of spacers and washers lying on the ground. Move the loose bits out of harms' way, GENTLY move the wheel toward the swingarm, and it should drop to the ground, and roll out beneath the fender. BE CAREFUL NOT TO LET DEBRIS GET ONTO THE EXPOSED DRIVE SPLINE ON THE FINAL DRIVE, THE MATING SPLINES IN THE WHEEL, OR INTO THE BEARINGS. Those areas are really, really, really difficult to adequately clean after they've been contaminated. It's a good idea to lubricate the drive splines in the rear wheel and the mating shaft in the final drive while the rear wheel is out.

Reassemble in the reverse order, torque specifications for the axle nut - 110 ft.-lbs. (150 nm), for the pinch nut on the swing arm - 17 ft.-lbs (23 nm). Bolts for the caliper should be torqued to 30 ft.-lbs. (40 nm).

Sounds like either wheel bearins or the spacer is missing