Fuel tubes

[Bodd]

Where do the two 3.5mm x 600mm fuel tubes go to ? Numbered 4 in the top picture and 2 in the bottom picture.

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[Drew400]

Hello Bodd,

I'm no expert, but on my basket case they simply dangled down behind the swing arm as vents, along with all the pipes from the float basins.

I will be able to locate a photo later today if required.

Cheers, D.

[Lobo]

Hi Bodd,
See here...http://www.sohc.co.uk/index.php/topic,6954.msg39452.html#msg39452

Top pic... they route over the top of the air intake box & then down over the back of the gearbox casing & between the swing arm.

You've only yourself to thank as you posted said pic!

Simon

[Bodd]

Cheers guys, I thought they went that way but as they are listed as "fuel" tubes I wasn't 100% sure. Another question about the part I circled in the picture below which has no part number, the part that the fuel pipe connects to is attached to a tube that rotates around the link pipe, on mine it seems very loose (rotates very freely), is that normal or is it a potential leak ?

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[Lobo]

Hi again Bodd,

On my carb rebuild I too noted the rotation .... would never have described it as 'very loose' but 'exactly as I'd expect' given the o rings nipping it into its carb housing. Certainly it'd never rotate under its own weight + fuel tube, but rather adjust nicely to its most comfortable position & stay there.
You got the correct sized 'o' rings?

Simon

[Bodd]

I thought it was in two separate pieces like in the drawing below but after stripping it down I found it's not, it's one solid piece with 2 O rings on each end ( it's a long time since I rebuilt the carbs), I've changed the O rings for some new ones and now there is quite a bit more resistance when I move it.

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[Drew400]

Can I slightly hi-jack your thread by asking if the piece shown as no. 108 in your diagram is designed to simply act as a balance between carbs (i.e. sharing air/fuel vapour rather than liquid fuel)?

Thank you, D.

[Bodd]

Can I slightly hi-jack your thread by asking if the piece shown as no. 108 in your diagram is designed to simply act as a balance between carbs (i.e. sharing air/fuel vapour rather than liquid fuel)?

Thank you, D.

In the parts list it's called "tube, fuel, 2.5 x 16", I don't think it carries liquid fuel as the part circled below does that.

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[Drew400]

Me too thanks.

I'm doing a similar job now on my carbs. I think I finished putting them back together yesterday and will one day put them on an engine.. that's the next big sub-project in my money pit heaven!

Cheers, D.

[Bodd]

Not a fuel tube but not worth starting another thread, as I am using K&N pod filters where do I route the breather tube (331 in the picture) ? I still have the filter box on the bike but there won't be a filter in it.

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[Lobo]

Hi Bodd,

There ought to be a frame clip on the spine bottom; from here how's abouts simply clipping / tying it to the RHS frame downtube forward of the battery and thence between the gearbox & swing arm to vent to atmosphere. Don't have the bike nearby... just a guess.

Whatever you do remember oil (mist) will be trying its hardest to coat your back wheel.... so ensure the vent is offset & pointing outboard as far as possible.

750 chaps... doesn't one model vent from 1/2 down the swing arm? Or did I dream that?
Simon

[Bodd]

I was thinking of refitting the chamber breather and attaching it to that but I thought it might be spraying oil mist into the empty filter box, preferable to spraying it on the back tyre but still not good, I might just get a filter and use the proper route and connection.

[Lobo]

Slight glitch with venting to the empty filter box is that the mist is not being sucked back into the air manifold box / reingested into the engine... and so will have to go somewhere else. And thus it would likely pool into liquid oil, and thence exit down the necessary vent / drain tube.... and out ahead of the rear wheel. Possibly a worse situation...
On the flip side bike crankcases have vented directly to atmosphere for decades; and often likely ahead of their rear wheels.
No one's verified yet, but I'm pretty sure one of the later K (750) models vented some way down the swing arm.

[Bodd]

Thanks for that Simon, I think the best idea is to make a guide clip to hold the end of the tube so it points out of the side away from the wheel.

[Dan]

If you're keeping the original filter box you could route the hose to a catch tank with a filtered vent hidden within said box. May need a longer hose but that would make periodical emptying of the catch tank easier. Looking at your RD and CB blogs I would imagine you could do this quite easily and there's no risk of oil mist getting on the rear tyre.