have done quite a bit of internet searching but I still dont have a definitive answer. I could buy 2 belts - but I am Scottish and as such very miserly that way.

My Beach Buggy engine is an unmodified type 1 July 1971 F Series 1300 Single Port. VW museum code F: 40 DIN P3, 1.3 Liter

It has a fan belt on it which is fine but it doesn't have any markings so I dont know whether its a 900 or 905 size. It has a dynamo not an alternator and its 12V

So I could buy both and just try it - but I thought I would see if anyone knows the true answer to this vexing problem.

My thinking is that its probably 900 but then again it could be 905... Someone somewhere surely knows... Confused

Dave

905 is standard length if all original the problem is after market pulleys which mean the belt is too loose hence the 900 mm ones.

Whip the existing one of and a half decent car place, probably even Halfords, should be able to identify a matching one