TOPIC:

Hi all,

Amongst the spares that came off the bike I found two virtually identical rubber hoses, inner diameter about 10mm. They look like breather pipes. Anyone any idea where they could have come from?

I know one of them is for the radiator 'overflow' to the reservoir bottle and the diameter and length seems to be right for that purpose. But the other one?

My first thought was that it was the tank breather pipe, but its way too long for that and there is no breather valve attached - in fact I think the bike didn't have that at all when I got it. Do I actually need a breather valve or can I just let a pipe hang loose?

Second thought was that they connect to the two reed valve covers on top of the exhaust side of the cylinder head. I found an old post in the forum by Bill who explained they linked to the air box somewhere, but I cannot find that connection in the parts manual. In fact, there is no mention of any rubber hoses connecting to those valves on top of the cylinder head....?

However, the diameter of 'my' rubber hose is too small to fit over the valve outlets. Also I seem to remember when I got the bike, there was a Y-piece that connected two short rubber hoses into a single one, but that seems to have disappeared. My bike did not come with the valve covers or an air box, so in my ignorance I may have thrown that rubber tubing away as obviously it was simply loose in the frame, not connected to anything......

Anywho... where should the two vents connect to (in absence of an air box)?

Lastly, there is a small breather pipe coming out of the top of the block, just underneath the carbs... L-shaped. Looks like it goes into the air box, but as I don't/won't have one, so suggestions as to where it connect it to welcome!

Apologies for the long post and many questions!

Cheers, as always!

Paul

small breather pipe coming out of the top of the block, just underneath the carbs... L-shaped. Looks like it goes into the air box,

That would be the OEM crankcase vent and it would have connected to the air filter box assembly.
One of these will work:

Pictures might help answer the other questions

It could be the pipe that fits onto the Round Cover that fastens under the fuel tank sender unit positioned above the far right hand carb (as you sit on the bike) ?

Pete F
UK

scotch wrote: Pictures might help answer the other questions

Myeah, point taken. I have no pics of the hoses yet, but here is a pic of the bike as bought and you can see one of them going from underneath the fuel tank to the water reservoir...

You can also see there is no fuel vent pipe...



The other rubber hose is identical, shape, size and length.

strate6 wrote: It could be the pipe that fits onto the Round Cover that fastens under the fuel tank sender unit positioned above the far right hand carb (as you sit on the bike) ?

Pete F
UK

Erm... I don't have the stock tank. Mine is off a Zephyr 1100.

But according to the parts manual, you might be right! Its a bit long for that though.. and I am pretty sure my tank did not come with a fuel sender, so it would have been another loose hose... . which I would have chucked along with the other one.... probably

Anyway, if I can't find out what/where on the second hose, I'll just go without and see what happens.

In the meantime, any ideas on where the cylinder cover vents should connect to, or should I use a similar solution to as what Scotch suggests? Or maybe connect to the crank case breather maybe, or will those work against each other?

The Technical answer to your question is explained on page 180 of the service manual