I got a used FA-40 and I got a question in regards to the nipple coming out of the rear cover below the carb. What is it for? When I received it had a piece of fuel tubing attached to it, but I have no idea what its for. Can someone shine light on this please? Also what should the valve lash be on this motor?
Thanks!

That nipple is common to most 4-stroke engines. It is an oil bleed and unburnt oil will be bled from the crankcase through it. Attach about 4 - 6 inches of fuel pipe and lead it away from the airframe if possible as it will make a mess!

A source of info you may find useful is at http://saito-engines.info/

Richard

Thanks Richard!

What about valve lash? How many thousands of an inch should they be set at?

The valve lash should be set at 0.03-0.1mm (0.002 - 0.004").

As stated above the nipple on the backplate is essentially the crankcase breather. Ambient air needs to be pulled in and pushed out of the crankcase in order the for the piston to move up and down freely. A buy product of this is that the oil in the crankcase also will weep through this nipple and so a length of fuel tubing so it exits the cowl helps to keep everything nice and clean.

Pete

Can I use that nipple to inject after run oil? Or somewhere else?

WB, I've been injecting oil into the crankcase that way for years, some will come out through the front bearing but that won't hurt a thing. I use NAPA Fogging Oil in an aerosol can. It works great. FA .40 on the right.

WB, I've been injecting oil into the crankcase that way for years, some will come out through the front bearing but that won't hurt a thing. I use NAPA Fogging Oil in an aerosol can. It works great. FA .40 on the lef.

Cool, thanks