Hi i have recently bought a 1973 puch maxi, My friend got it started 2 weeks ago, but has now said it wont start. When you pull on the started lever it is really hard to pedal. Ok when lever is release. Can anyone help me out here. Im not mechanical minded but good when i get shown step to step on how to do it, like videos or pics. So if anyone has any ideas on what could be the porblem and help me out that would be great. Thanks x