by vanfox » Wed Apr 25, 2018 11:39 pm
I strongly suspect the belt was fitted incorrectly. ( When I had my first van I took it to a garage to have the belt changed. Be ready at 4 o clock, they said, I turned up at 3.30, they were using levers to get the belt on!! Fortunately it ran until I sold it but since then I've always done my own belts, but I digress.)
The garage says they checked the "timing marks"....b******s! We use pins on the Di, there are no visible timing marks, makes me think they used chalk marks instead of pins. Maybe they didn't loosen the 13mm bolts on the IP pulley whilst setting the tension. As has been mentioned the IP can retard itself once the belt is off if not pinned, the belt could be one tooth out. I've dabbled with timing, retarding the IP gives the same result you have.
Possibly all you can do is go back and ask to see the pin set they used then insist on watching whilst they refit the belt ensuring they use the pins and loosen the IP pulley bolts. It's possible they disturbed some thing electronic with it being an Epic, who knows?
Changing the belt should make no difference to how the motor runs, it's only done for reliability.