That depends where the number is located, if on the head ignore that on is it the same casting as 303 head on the outside, look on the crankcase near the starter under the air box, you will see the end number 818303*nnnnnn should be seen.
Thank you. I did have a look and it is very difficult to get a clear view without taking the air box off as it is very well hidden, but form what I can see it could very well be 818303 ....
Then my question is why is there a different number on the head (or just below it)?
I attach a photo of that number as it is very visible. the one you mention is too difficult to photograph.
Thank you for your help.
Sorry this obsolete forum system doesn't allow me to upload a photo, in any format and size. It's infuriating!