Various breather pipe questions

[Graeme77]

Im a bit confused about some of the pipework on my 76 cb750 F1.

first, the clear breather from the rocker cover, where does this go to?

Second, my bike has the breather can under the battery, but its not connected to anything. My parts book suggests its linked to the air box, at the top, but my air box has no connection for it. My air box has cb750F written on it so i guess its the right one.

Third, my carbs dont have the pipes on the breather/balance outlets on carbs 2/3.
Carb 1 is linked to carb 2 with teh short pipe, 3/4 are connected too, but teh 90 degree outlets in the middle of carbs 2 and 3 have no pipes.
Are these important? Do they connect, or just vent to atmosphere?

Fourth, there is a pipe underneath the tank, i assume this is the tank vent.
It comes back as far as teh rubber tank hold down but no further. Should this be longer and vent down by the swingarm like the carb overflows?

Thanks.

[mick]

Hi Graeme, i can answer a couple of your questions, the 2 pipes that come off your carbs they just vent to the atmosphere & the pipe under your tank is just a drain and on mine it has a junction at the rear tank rubber then goes down and under the bike , hope this helps cheers Mick.

[Graeme77]

Thanks.

I have a sealed battery, but im still not happy with teh tank vent ending at the battery, ill add extra and route it down further.

As for the carbs, i guess there ok left without pipes then? Might add some for completeness, but if there is no need for them its neater without.

Just the air box/breather to sort now. My parts book shows a pipe on top of the airbox, but as i say, mine doesnt have it.

Even though it says cb750f, could it be the wrong air box? It has 2 small air inlets, one at the front, one at the back.

[UK Pete]

I am pretty sure the large pipe coming from the tank is a drain pipe for any water that gets under the petrol tank filler flap , it should be two part and joins where the battery tray is, and then goes down behind swing arm

This is the set up for the F2 which is almost the same as the F1 apart from the the breather condensate trap is a bit bigger on the f1



Pete

[Graeme77]

Thats a better view, i wonder why i have the trap but the air box has no connection?

[K2-K6]

Just a little oddity is that the K2/K6 have the side panel badges "750Four" so it's possible that the airbox would be labelled like this even though it came from a K model, I've never looked at this on the airbox though.

Carb vent pipes are ordinarily put to under the bike so that no significant amount of fuel would collect on the engine if a float stuck open and so reduce the risk of a bigger fire if that too happened.

The tank pipes are split normally I think so that if you work on the bike then taking the tank off would not involve threading all of the pipe back down through the bike when re-fitting.

[Spitfire]

Here's some more info on the F1 breather pot.

Cheers

Den

[Spitfire]

The overflow pipe from my tank goes from the tank to a join by the battery and then runs down the frame and comes out near the main stand, this is the way it was run from new, the pipe in question is the clear (yellowish) one in this picture.

Cheers

Den

[simongi]

Thanks for all the info. Have managed to get a breather from the states through Ebay. The element requires replacement but now its ready to go. Cheers guys