Motorcycle Repair: 1965 honda s65, intake leaks, intake tubes

Question
I am replacing the piston and cylinder can you tell me what the function is of the B oil pipe that goes from the carburetor to the side of the cylinder. Thanks

Answer
Hi Morrie,


One oil line is the feed and the other is the return line.
I think they insulated the feed line to keep the oil warm
on the way to the carb. If "B" line is not insulated
then it is probably the return line to the crankcase.

The oil lines were used on engines with long intake tubes to prevent the carburetor from icing up.
The warm oil helped to prevent icing and also helped the fuel to vaporize more easily.

Icing is not as common on shorter intakes tubes so the oil lines were eventually abandoned.

The carb intake flanges often warp and leak vacuum so they can be sanded on a flat
piece of thick glass to restore them and prevent intake leaks later on.

Let me know if you need more info on the rebuild.

WS
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