LN-25 jumping speeds

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I have a older Lincoln LN-25, at times it works just fine, but just then when you pull the trigger, it's like the wire comes shooting out fast. I have the  High/Low switch on the low position,  I have had it apart and cannot determine the problem.  Any ideas?
Reply:Hello Mulley, a couple of questions concerning your gun/liner/contact tip set-up. Are you using a liner that is designed for say, .072 wire? and if that is the case are you running smaller diameter wire through it without changing the liner to match the smaller wire diameter? If so, by operating your gun with the oversize liner and even using the proper tip size, you could possibly see this sort of thing happening due to the wire "loading up" inside of the liner behind a slightly worn and sticky contact tip. When undersized wires are used in oversized liners the wire will possibly "snake". Another indicator or this sort of condition will result in excessive wire stick-out when welding has ceased. If the contact tip is new and readily allows wire to feed through it the wire may look like a sine-wave while welding is taking place, as soon as the trigger is released the waviness of the wire will straighten out, hence the excessive stick-out when welding ceases. Alternatively, if the contact tip is worn/sticky, the wire could be held back by the sticking in the contact tip until enough wire has snaked behind it to cause the wire to move, at this point it might build up enough pressure to cause a surge of wire to be pushed out until it is able to find a neutral drive point. If you are already aware of this sort of condition I totally understand, just looking to give some perspective that you possibly hadn't considered. Best regards, Allanaevald
Reply:I understand what you are saying, but it is the same liner the problem started on is own, always ran .068" flux core.  But I will certainly look into that.  Thanks for your reply.
Reply:I had one do that in the rain.  I took out the wire speed pot and cleaned it off.  This was at the jobsite.  It has worked fine since ( a couple of years ago).David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Mulley, if it is a liner problem often you can feel it binding up in the whip. Just my own 2 cents but I think lincoln whips are junk. We run profax whips and relace liners or blow them out at least every couple of rolls.  When in doubt I also keep a couple spare goosenecks on hand. It seems to me like I have a lot less problems with shorter whips and shorter goosenecks.2011 Dodge 3500 diesel duallyLincoln SA-200Lincoln SAE-300LN-25'sLincoln Idealarc R3RMiller Trailblazer 302
Reply:oops double postLast edited by pilebuck; 03-22-2010 at 09:31 PM.Reason: double post2011 Dodge 3500 diesel duallyLincoln SA-200Lincoln SAE-300LN-25'sLincoln Idealarc R3RMiller Trailblazer 302
Reply:Thanks for the reply, Daid and Pilebuck, Dave what is the wire speed pot? The motor with the drive rollers?
Reply:Hello Mulley, it is the rheostat that is located behind the front panel on the other side of the wirespeed control knob. Regards, Allanaevald