Lincoln Power Mig 255x welding funky

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I have a fairly new (less than a year old) Lincoln Mig.  It usually welds wonderful and haven't had any trouble with it until just recently.  It is being used in a teaching lab at a highschool so it gets used quite a bit.  Anyway, for whatever reason, it is welding choppy now.  It is like the wire isn't feeding out right or hanging up.  It is almost like the voltage drops and it starts spattering.  It is a new roll of wire, new electrode tip, and new nozzle on the machine.  We noticed a problem and quickly decided the liner must be dirty so we bought a new liner and installed it.  Same problem is occuring still.  Also noticed that if lead has the least bit of curl or a loop in it the problem is worse.  A few months ago you could have tied the sucker in a knot and it would have still welded properly.I'm at a loss as to what to do next.If you don't use your head you may as well have been born with two backends.That ain't exactly how Papa used to say it.*Linc'n WeldanPower 200 with a Wis. 2 cyl. w/handcrank*Linc'n AC225 *Linc'n ProMig 180*tiny porta torch...
Reply:If you have made sure there are no problems with the gun.Test the trigger wires in the gun to the weld circuit, should be no connection.After you have cleared the gun. you have 2 choices.1 call Lincoln direct.2 find a Lincoln warranty shop and take it in for a free repair.It is possible that one of the SCRs or the control pcb may have failed.unplug welder, remove cover, inspect for loose and burnt connections.clean out the dust and dirt. and cut off pieces of wire.If you find a burnt connection call Lincoln before repairing.
Reply:Originally Posted by ccawgcIf you have made sure there are no problems with the gun.Test the trigger wires in the gun to the weld circuit, should be no connection.After you have cleared the gun. you have 2 choices.1 call Lincoln direct.2 find a Lincoln warranty shop and take it in for a free repair.It is possible that one of the SCRs or the control pcb may have failed.unplug welder, remove cover, inspect for loose and burnt connections.clean out the dust and dirt. and cut off pieces of wire.If you find a burnt connection call Lincoln before repairing.
Reply:The liner is MUCH too short. We have a bunch of 255Cs and other machines with Tweco-style and Tweco guns.The liner should be long enough to go into the base of the diffuser and resist the diffuser slightly when it it is tightened by finger. Snug with wrench and you're done.I don't worry about tightening the allen-head setscrew in the diffuser (but make sure it isn't in too far where it would block the liner). The threads on the base of the diffuser are sufficient to seat it against the liner end.
Reply:Bluesman,Did you get your liner replaced properly and did that fix your original problem?  I am wondering because of a similar problem I am having with my Power Mig 200.Thanks,tkingDenver
Reply:Liners are certainly a "consumable", and since they cost less than 20 bucks I don't hesitate to swap them out. One way you can "feel" a very worn liner is to (cleanly) cut the MIG wire before it enters the feeder and (after unscrewing the MIG gun tip) pulling the wire out of the gun from the gun end. It will often feel rough/sticky when the liner is bad. Make sure the new liner is CLEANLY trimmed (I like cutoff wheels).
Reply:Do not use cut wheels to trim liners. This leaves a razor sharp edge at the end of the liner.This edge will shave the wire and plug up the contact tip. Use a large wire cutter. Side cutter, diagonal cutter to trim a liner. Just split the coils, bend  liner over 45 degrees and cut.This leaves and clean end with no burrs. worst case you will only have to trim the end of the coil wire back so it will slip into the diffuser with out catching. Quick touch on the bench grinder. Liners that are to short or to long will cause feeding problem. Many times I have trimmed 1/4 inch off a liner and now the welder was feeding great. If you use your contact tips to long. Then weld current is pulled off the liner. This arcing turns the inside of the liner into sandpaper and the wire will stick to it. Move the miggun and the wire will pop out some.
Reply:Got the new liner in.  Ran wire through it and now that sucker welds like it is supposed too.  Don't know what those crazy morons at the factory were thinking when they put that short liner in.If you don't use your head you may as well have been born with two backends.That ain't exactly how Papa used to say it.*Linc'n WeldanPower 200 with a Wis. 2 cyl. w/handcrank*Linc'n AC225 *Linc'n ProMig 180*tiny porta torch...