I have a 6250 I'm fixin' up and the last detail is the front electromagnetic coupler. The thing opens easy-peasy but doesn't always shut. By applying my scientifically oriented analysis skills, I held it pointing straight at the ground and the knuckle simply would not close - jammed in the full open position. Tilt it back and point it at the sky, and it closes finer than frog's hair. Conclusion?
I thought it had a broken plunger spring, so out comes the knuckle rivet, the knuckle, a worn knuckle spring (the two arms of the spring are parallel), the plunger and the plunger spring. The plunger spring looks slightly compressed but definitely not broken. Checking the knuckle, I can see witness marks where the plunger hits the rear part of the knuckle. I gently filed the rear of the knuckle silky smooth, then I chucked up the plunger in my drill and smoothed off the business ends, adding just a wee bit of rounding to the small plunger edges. I didn't have a new plunger spring so I carefully stretched the old one just a bit. Reassembled everything, adding a new knuckle spring in the process, and it now works much better, but still is a little hard to push closed in the "straight at the sky" position - no lube of any kind was applied - I'm 100% certain a small drop of oil would make things silky smooth, but oiling a coupler just doesn't seem like a good idea.....
I did not clinch the knuckle rivet at this point, hoping to hear back from one of ya'll who may have encountered and solved this problem previously. Watcha got?