You may be able to get another drawbar from Yardbird Classic trains. If not, a piece of styrene plastic could be used to make a drawbar (must be insulated so there is no electrical contact between the engine and the tender except for the wire between the motor and the tender. I may be wrong, but I think the crosshead guide on the left side is not connected correctly to the cast part that projects out (on both sides of the chasis) to hold the stamped crosshead guide. The left crosshead guide seems to be jumping up and down as the loco runs. Another thing that may contribute to jerkiness is that the wheels may not be clean, especially the tender wheels on the left side of the tender trucks. Also, you may want to remove the tender trucks and lightly polish the bolsters on the tender chasis, where the truck bolsters contact the tender chasis. Also polish the contact surfaces on the tender trucks. You might want to see about buying or making some brass contacts that rub lightly on the tender axles, providing better contact than the wheels and axle points alone. You need to be sure the righthand locomotive drivers are clean. It is possible that the drivers are out of quarter, though IMHO this is less likely with Mantua locos, even old ones. Not unheard of, however. The only way to check this is with a quartering tool, but I would leave that until nothing else works. Be sure the worm is clean of old grease, and the bull gear on the driver should be checked for hardened lube and cracked or broken teeth. Be sure the commutator on the motor shaft is clean. You can do this by taking very fine emory sandpaper and folding a piece so you can fit it in to touch the commutator. LIGHTLY press the paper against the commutator surface while running the motor. It shouldn't take much. Also, check the brushes for wear. Also, look to see if the motor shaft is bent, which would cause the worm to provide inconsistant engagement with the bull gear. Hope this helps. If not, come back on line, and we'll see what else we can suggest...or do...to help.