1965 Honda 65 - mystery oil lines

[Daox]

This past weekend I was working on my dad's old motorcycle, a 1965 Honda 65 (yep, 65 cc monster, woo ). I've ridden it a few times, but it hasn't been started in years. Here is a pic I found online, looks very similar and its still in great shape considering the age.




So, I took the carb off and cleaned it up. However, while doing that I noticed two oil lines that I can't figure out what they are for. One comes from the crankcase up to the carb, and then connects to the other line and it goes back down to the side of the engine block. I'll get exact pictures, but here is one I found online and marked up.

Any idea what these lines are for? I'm thinking they might be using the vacuum to pull oil up for oiling... something. I've just never seen something like it before.

[MetroMPG]

Cool bike. Can't help you though - sorry!

[Old Mechanic]

Probably using the hot engine oil to get better atomization of the air-fuel mixture. Could also provide some cooling of the engine oil by transferring the heat to the incoming air-fuel mixture.

Those variable venturi (SU type) carburetors are very prone to icing. In some versions the "choke" is simply a means of moving the seat a significant distance from the needle, instead of a butterfly that actually restricts the airflow into the carb.

Pure speculation on my part.

regards
Mech

[Daox]

This one does have a spring loaded butterfly for the choke.

I'm wondering if it isn't just the heat thing though. Come to think of it, I don't exactly recall there being a hole from the oil passage to the air passage going through the carb... Perhaps the oil is pumped through it.

[Ryland]

If you look under 1965 S65 right hand crank case cover you can see the lines you talk about, one of them looks to have either a filter or a check valve?
No label as to what they are tho as they are out of stock.http://www.mrcycles.com/fiche_section_detail.asp

[Christ]

This fiche from BikeBandit shows them as "oil hose A" and "oil hose B", but again, out of stock.

Chances are, earlier posters are correct, and it just uses heat from the oil to help vaporize the fuel or heat the intake air charge.

Honda's always been famous for that kind of stuff, anyway.

[Daox]

Yup, those are the oil lines. Heat makes sense.