The clutch of my dt125 is hard to sqiz, is it the

How motorcycle clutch works very interesting motorcycles

It sounds to me like the inside of the clutch cable itself has broken strands that is making in bind up. Disconnect the cable at the motor (transmission) now see how difficult it is to squeeze the clutch lever on the handle bar. If it is easy to pull back and forth than the clutch cable needs replacing.

You can try adjusting couch cable to specs. If that don't do it you may have to adjust cluch throw out bearing, to specs.

1. Clutch Lever
   • As the clutch lever is operated over time, it gradually loses its grip on the clutch cable, weakening the clutch lever action until it barely moves the clutch plates. Maintain the clutch lever by ensuring the free play at the lever meets the specifications of the motorcycle's user manual, in which you will also find instructions on how to make this adjustment.
     
   Clutch Cable
   • Unlike the gradual onset of a clutch lever problem, the somewhat uncommon failure of a clutch cable is instantaneous. With little warning, the clutch lever goes completely slack and the clutch will be inoperable. Keeping a clutch cable well lubricated can prevent failure. However, in the event of a cable failure, a registered dealer should fit a replacement.
     
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   Clutch Plates
   • Problems with the clutch mechanism itself normally manifest themselves in the gear change rather than in the applying and releasing of the clutch lever. Noise, chattering or slipping can be the result of misaligned or warped plates, leaks in hydraulic cables or bearings. Although more serious, if recognized early, these problems will be relatively inexpensive to repair.
     

You might be able to improve the situation a bit by getting a little oil inside the cable housing. Get some WD40 with the little tube on the nozzle. There might be several places where the cable enters a cable housing. There might also be a couple of places where the ***** cable has to slide through a groove, like under the pedals. The trouble is that you have to pull the cable hard enough to move the chain, and overcome the spring that is pulling on the other end of the cable, AND overcome the friction that increases the harder you pull on the cable. A little bit of dirt or corrosion increases that friction A LOT. AND there is one more source of friction you have to overcome - the shift lever itself has a kind of friction clutch built into it to keep the cable from slipping back and shifting to a higher gear by itself. You might be able to loosen that clutch a little, but there are hundreds of varieties. Some shifters have a ratchet built in so the clutch only adds friction in the direction you need it - if you have one these, loosening the clutch won't help.
Good luck!

Turn clockwise the tensioner on your left lever all the way in.Loosen up the 2 nuts on the clutch cable's bottom end.Pull the **** (not especially hard though) and tight the nuts back.Then go to your lever's tensioner bolt and adjust the cable so that the lever's end (ball) should move 2-3cm before the cable stretches (freeplay 20-30mm)

Try tighten cable adjusters, check cable for damage, check the clutch release arm for damage, if thats ok its worn clutch plates replace the clutch plates and check components for damage,

To remove the old cable first shorten the mid-cable adjuster to give as much free play as possible. If you need more free play screw in the adjuster at the clutch lever as much as possible and line up the slots so you can disconnect the cable from the clutch lever. Then remove the shift lever, and possibly the left footrest if needed to remove the front sprocket cover. Remove the cotter pin and disconnect the cable from the clutch release lever. Make a note of the routing of the old cable so you can replace it. Install the new cable with a new cotter pin at the lower end first, and route it the same as the old cable. To adjust the new cable, shorten the mid-cable adjuster as much as possible. At the clutch lever, turn the adjuster in and leave about 1/4" of threads showing between the locknut and the lever body. With the front sprocket cover still off, loosen the locknut on the clutch release lever and back the screw 3 or 4 turns. Turn the clutch adjusting screw in until it becomes hard to turn and then back it off 1/2 of a turn and tighten the locknut. Now lenghten the mid-cable adjuster until there is no free play and tighten the locknuts. Check that the lower end of the cable is fully seated in it's socket. At the clutch lever, turn the adjuster in so you have 1/16" free play, and tighten the locknut. Replace the front sproket cover and the shift lever and footrest.

There should be about 1/8" end play on the clutch handle. Adjust the cable at the handlebars where the cable goes into the clutch lever housing. Screw the adjuster inward until the end play is present. Some bikes have an adjuster at the gearbox where the cable hooks up.