How to get crankshaft out of kx 250 2004 model

get the new sensor then you know what your looking for and how it fits etc, the crank sensor is located at the gearbox end of the engine it will be bolted/screwed to the end of engine block immediately over middle of gearbox with a wire connector coming from it you should be able to change this part without removing anything else but to give yourself a better view removing the air filter assembly is not very hard at all and will give you a bit more room if you think you need it after locating the crank sensor

I would say that you have made an error in fitting the gear box that is jamming the flywheel to tight IF the gearbox didn't go all the way in so that the housing touched the rear of the engine all the way round then the clutch shaft has not fully engaged the spigot bearing in the crankshaft causing the problem. Loosen of the bell housing bolts until you can turn the flywheel to see if that is the problem.

YOU NEED TO REMOVE FLYWHEEL REMOVE OIL PAN. REMOVE REAR OIL SEAL HOUSING BOLTS. USING THE PRY POINT LOCATED AT THE EDGE OF THE CRANKSHAFT REAR MAIN SEAL HOUSING SHEAR THE RTV SEALANT. REMOVE THE REAR MAIN OIL SEAL. INSTALL GUIDE PINS INTO THE TWO CRANK SHAFT REAR OIL SEAL HOUSING CORNER BOLT HOLES OF THE ENGINE BLOCK.INSTALL THE CRANKSHAFT REAR SEAL INSTALLING TOOL ONTO THE REAR OF THE CRANKSHAFT FLANGE. APPLY A 0.2 INCH 3MM BEAD OF SILICONE SEALANT TO THE REAR OIL SEAL HOUSING . INSTALL THE REAR HOUSING TO THE ENGINE BLOCK.REMOVE THE GUIDE PINS AND INSTALL THE HOUSING BOLTS TIGHTEN THE BOLTS TO 89 INCH LBS. REMOVE THE REAR SEAL INSTALLATION TOOL FROM THE CRANKSHAFT FLANGE.THEN INSTALL OIL PAN AND FLYWHEEL.

Normaly you can remove the left crankcase on its own, however if it is proving difficult to split it is possibly tight in the crankshaft main bearing, you will need to remove the clutch at some point during this rebuild so do it now while you have the stability of the engine cases , undo the nut securing the crankshaft pinion on the r/ h side, the crankshaft is often easyer to remove from this bearing, also it is easyer to reasemble the engine and gearbox when previously dismantled correctly. Paul

you need to remove the engine. your flywheel is bolted to your crankshaft

remove the outer small bolts to remove balancer(pulley) the big centre bolt holds crankshaft gear for timming belt which slides off with timming belt removed.

What type of air compressor do you have?
Is it a single motor\pump combination is the pump and motor separated by a fly wheel? If it's the first one don't waste your time or your money. Hard to find parts hardier to justify the money if you do.
If it's the second then you should make sure you can get a rebuild kit and replacement parts. If you haven't already.
Assuming you have anyone of the more common pump brands like Dayton, Champion, Ingersoll Rand.
Dis-assembly should start with the top end. Remove the head and valve plate then the cylinder head bolts and cylinder head. Remove the wrist pin\pins and piston\pistons. Next remove the lower rod end caps and pull them out taking care not too nick the crank bearing journals. Remove the front crank cover and and (if it has one) the rear bearing cap\plug. You should be able to remove the crank through the front access. You may need to tap the back end of the crank clear or the rear bearing.
The bearings will probably need to be pressed out.
Unless you have a pump that is considered non serviceable or is an oddity this should do it.
If your pumps layout differs from the norm or you just need more specific information please let me know. Just include the make and model and I'll be glad to help you out. Good luck.

you need to peg the crankshaft near your gearbox. There is a hole in engine block for this purpose. Find this hole and insert an allen key (thick enough to fit in there). Turn the crank pully with ratchet in clockwise while try to find out the locking hole in crankshaft near gearbox by pushing allen key through engine block hole. You'll hear a click and the allen key goes fully inside. Now your crankshaft is locked and you can open (anticlockwise) the pully bolt.

did you check the pulley on the crank shaft ??
is it warped ?? ( bent )
because i do not think that the truck will run with the crankshaft moving.....back and forth.
so in any case you have a lot of work to do.
here is how to remove the crank shaft.
REMOVAL

1. Remove the oil pan.
2. Remove the oil pump from the rear main bearing cap.
3. Remove the vibration damper.
4. Remove the timing chain cover.
5. Identify bearing caps before removal. Remove bearing caps and bearings one at a time.
6. Lift the crankshaft out of the block.
7. Remove and discard the crankshaft rear oil seals.
8. Remove and discard the front crankshaft oil seal.

INSTALLATION

1. Lightly oil the new upper seal lips with engine oil.
2. Install the new upper rear bearing oil seal with the white paint facing towards the rear of the engine.
3. Position the crankshaft into the cylinder block.
4. Lightly oil the new lower seal lips with engine oil.
5. Install the new lower rear bearing oil seal into the bearing cap with the white paint facing towards the rear of the engine.
1. Apply 5 mm (0.20 inch) drop of Loctite 518, or equivalent, on each side of the rear main bearing cap. DO NOT over apply sealant or allow the sealant to contact the rubber seal. Assemble bearing cap to cylinder block immediately after sealant application.
2. lb align the bearing cap, use cap slot, alignment dowel and cap bolts. DO NOT remove excess material after assembly. DO NOT strike rear cap more than 2 times for proper engagement.
3. Clean and oil all cap bolts. Install all main bearing caps. Install all cap bolts and alternately tighten to 115 Nm (85 ft. lbs.) torque.
4. Install oil pump.
5. Install the timing chain cover.
6. Install the vibration damper.
1. Apply Mopar Silicone Rubber Adhesive Sealant, or equivalent, at bearing cap to block joint to provide cap to block and oil pan sealing. Apply enough sealant until a small amount is squeezed out. Withdraw nozzle and wipe excess sealant off the oil pan seal groove.
2. Install new front crankshaft oil seal.
3. Immediately install the oil Dan.

if you have an email address i can send some images