Topic: Breather Chamber - 75 CB750F

[GurgleMurgle]

I have removed the airbox and carburetors for some badly needed service on my 75 750F.  I’m sure I’ll have a million questions on that eventually, but for now they are set aside waiting for parts and more carb cleaner.   

So this is a good time for me to clean this poor greasy old bike.  There is a tube that runs to the top of the airbox from this breather canister contraption, which appears to be fed by a tube coming from the vent near the valve cover.   I’m imagining it collects whatever oil is entrained in the engine vent air, and allows whatever vapors that remain to be burned in the engine.   But I really don’t know - please educate me.

Maybe more importantly, do I need to do anything to service it?   I’m thinking whatever its purpose is, it’s probably gunked up pretty good.  Just like everything else on this thing. 

[ekpent]

When you say "parts" are we talking carb rebuild kits ? Its recommended here that if the carbs still have the stock brass and other bits inside to re-use after cleaning as many original parts as possible. You will find that these round top carbs are some of the easiest carbs around to deal with.

[GurgleMurgle]

Nice on topic response. This is why I hate the internet.

[Don R]

 The breather element inside will likely be crumbling, I replaced mine with scotchbrite, others have used similar materials or lawn mower air filter media. Anything that air can pass through, but oil might stick to. Check the rubber drain hose, it is closed on the bottom and opens to drain when you pinch it.
 It works pretty much like you mentioned. 
  (Caution; old man story to follow)
  Earlier models just drip on the road, I have noticed in old pictures of the highways there was often a black strip down the center of every lane due to road draft tubes dripping oil. In the 60's we were warned about riding motorcycles in the oil on center of the road.  It occurs to me we don't see that much since cars got better.
 Welcome GurgleMurgle, the F0/F1 is my favorite. My F owners tip is to keep the brake fluid fresh to maintain those disc calipers and master cylinders.

[ekpent]

Nice on topic response. This is why I hate the internet.

Why do you hate the internet ?

[Jerry Rxman Griffin aka MuthaF'er]

You are spot on for it's purpose. As Don states the drain hose, if original, requires a pinch to open it to allow any accumulated oil to drain.   

[Don R]

 It really is important to use the original carburetor brass if it hasn't been messed with, (as in drilled jets). Brass that's not kiehen brand is often off spec and can cause other problems, either lean or rich.
 The jet needles can be worn in high mileage engines but most often the original brass can be cleaned and re-used.

[Jerry Rxman Griffin aka MuthaF'er]

And the aftermarket needles/jets set are NOT the same as the -392 F part

[Don R]

 Jerry, I just cleaned up a set of F carbs, are you saying the f carb needles are different? I had asked about different needle numbers but didn't really get much info. I had thought the screened float valves were the main difference.

[Jerry Rxman Griffin aka MuthaF'er]

Don, the part number is different. My assumption was the needle was different. The -392 Honda replacement part kits that I accumulated (and used) came with the needle and jet but no screen. Probable different needle profile.

16012-392-004 Needle Set, Jet