CRazy250 said:
i wouldent worry about performance unless you are going to completely rebuild the motor.
I wouldn't rebuild the engine unless there is a reason to do so.
Parts and gaskets are getting very hard to get for those engines so I would not recommend taking it apart unless you have to.
First, adjust the valves and check the compression. If the compression is good then there are a few minor mods that can be done to improve performance. Remove the rubber deflector from the top of the airbox. Remove the spark plug cap and remove the resister from the inside of the cap and replace it with a piece of copper rod the same length as the resister. Also, when the plug cap is off, cut back the coil wire about 3/8 of an inch. There are jetting changes that can be made but I would have to look those up in my notes.
A major improvement can be made in the handling department by purchasing a complete front end off of a 1987 to 89 CR250. Much better forks and a disk brake. These can be found in motorcycle wrecking yards or on some of those online auction sites for $200-$300. They bolt right on.
The 83 xr350 is a fun little trail bike. The engines will rev to the moon and have pretty good performance in the higher rpm range. The performance is there, just twist the throttle a little harder and let it spin.
I believe the plastic from the '85 model will not fit the '83. On my '83 I cut the rear fender down and grafted a CRF450 rear fender on to the existing fender. Most any CR front fender will fit but, you will have to trim the rear of the fender to keep it from hitting the exhaust pipe.
Good luck. :cool: