the feed motor is the same as all the other sip machines but it does feed better than them
I'll give that a try tomorrow,If i remember rightly I dont think the motor has ever came close to stalling no matter how much tension i put on the rollers so it may well be the problem!Sounds like the feed wheels are slipping. The tensioners have been criticised on the SIPs, but some people on here have extended the range of the tensioner screw using a block of wood to good effect. Might be worth a shot. Clean the rollers with thinners too.
My SIP 130 that now resides in a suitable place, a skip in the the local dump, Portamig 181 arriving soon