I've got a brandy new 793 Hirth........well, you can't tell it from a new one in a crate.It's mint. Anyways, what oil ratio do I need to run in it? (New pistons/rings) An old manual sez 20:1 and that seem way too rich, even for break in. I'm thinking something like 40:1. Any recomendations? Thanks!

The quality of oils used back in that era were the reason for the 20:1 ratios. 40 or 50 to 1 with today's oils would be better. Break-in could be 20:1 though.

With good modern high quality oil you should be good at 40:1, that's what I mix for my antiques.

Thanks guys. Here's a treat

Moving this to the Vintage forum.

Hey ZIp....Run that honker rich...plugs are cheap....not 300 bucks a set like pistons...I have an nos 793 for one of my xx amf racers and I will not run it any leaner that 20 to 1.....Do you have an xx 1800? and tell me more about the picture you posted....I know the motor and clutch all right but Im curious about the chassis...thanks...Nick.

Wow that is cool! i bet it goes!