The driveshaft will not turn - 2004 Suzuki RM-Z 250

That sounds like one of the constant velocity joint on a driveshaft is broken, or the splined end(s) on the end of the driveshaft where it fits into the hub, have stripped.

The link below will show you generic photos of drivehafts/cv joints.
driveshaft cv joint Google Search

If the splined end of the drivehaft/hub strips, there's nothing to drive that road wheel. The driveshaft will just 'spin' but as it can't mesh with the splines in the hub - no forward motion.

Get somebody who knows what to look for to check both the driveshafts and identify which one is at fault.

What kind of car or truck? If both driveshafts turn, then you have a bad front differential. Remember there are 2 driveshafts on 4 wheel drive vehicles. Also do you ahve locking hubs?

put a mark on the tire and a mark on the driveshaft. raise the vehicle and install safety stands , put the vehicle in neutral have an assistant on hand to spin the tire one revolution , while you watch the mark on the driveshaft to count the revolutions. so let us say that the driveshaft turned 3.5 turns give you a ratio of 3.5:1

Be careful with recovered units. make bloody sure that it has no kinks and not bent - look down the shaft and turn it. If the last one fell out, sounds like the previous joker used one that was too short different models of the same marque can have different lengths.

If your machine has a removable panel underneath remove that panel and see if your belt has broken....If it is remove it and make a note of the number on the side of the belt ....it will look something like this....80S3M564 then e mail me at [email protected]

If you mean the shaft that runs the accessories in the front causing a chattering noise, No, you need to loosen the mounts that hold the whole front assembly in place to remove the coupling though.
If you mean the rear driveshaft, then yes, Lift the vehicle, select neutral gear, apply the handbrake and mark the driveshaft at the rear where the driveshaft connects to the differential so it can be re fitted in the same position. Loosen the bolts one by one, releasing the handbrake to turn the driveshaft around to get to the next bolt. Take note of which way around the bolts are as this is important for the strength of the bolts in relation to the sheering action of the driveshaft.

Its hard to understand what you are asking?The front driveshafts are attached to the wheels. the rear wont turn if the wheels are on the ground. I would never buy a car with parts disconnected. sounds like BS.

Check the splines in the yoke. You will notice that you have a gap. That gap lines up with an extra wide slpine on the transmission output shaft. Once you have them lined up it will slide right in. Then if you need to turn the driveshaft to get the rear universal to line up with the rear yoke, simply put the trans in neutral and you can turn the driveshaft. Hope this helps.

You have a problem in the diff. I cannot believe they replaced the drive shaft without further inspection. You are driving it so axles are O K, will be pinion brgs.