Last week my MM 130 stopped feeding wire unless the gun cable was held straight in front of the welder.

The feed roller was tight on its shaft and turning. I replaced the contact tip and tried tightening and loosening the compression knob and also checked the wire roll but the problem remained.

The gun and cable was replaced no more than 20 lbs of wire ago so there should be no liner problem.

Next, as I use a felt lubricator on the wire feed, I removed it and rinsed any residual oil away with brake kleen. (I have occasionally squirted the wire lube directly onto the wire coil as this unit has always had feed difficulties)
The problem remained.

Taking all of this together, the feed roll needs to be replaced and I have a new one but not installed it yet. (i'm traveling at the moment) Comparing the old to the new, the old roller does not seem to be worn even when under magnification.

Finally to the problem: the roller has a straight groove on one side and a knurled groove on the other. The roller is embossed with ".23 - .30" on the groove side of the roller and ".30 - .45 on the knurled side. (see photos) this seems to indicate that the choice of grooves is based on wire size.

The manual, however, says to use the straight groove side for solid wire and the knurled groove for flux core. (see photo)

To further complicate the matter, when installed, the wire passes over the groove on the inside of roller thus leaving the embossed wire size of the vacant outer groove visible, i.e., does the visible wire size numbers relate to inner groove being used or to the vacant groove on the same side as the embossed numbers?

How should the new roller be installed for .30 solid wire? The roller markings and the manual seem to directly contradict one another.