Why's my motor sticking??

[loose]

Hi can anyone help? got an old Spashett 11 double that for some reason has decided that it needs a push to get going.

Basically from a standing start nothing happens when you hit the throttle. Give the car a nudge or just turn the shaft and away it goes no problem. Can come off the throttle and as long as the revs dont stop altogether its fine when you get on the throttle again. Let it come to stop though and it wont start again.

Sorry if that sounds a bit confusing. Any ideas?? Brushes look fine.