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Carb connection pipes

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Any advice? I'm putting a pair of monoblocs on my 88SS. Just a point of detail...do owners advise or prefer the pipe between the bottom banjos to be straight between the carbs, or looped back? I'm using new rubber tubes, so won't be able to see air locks...if indeed they don't just get pushed through. One carb has chopped float chamber...hence the bottom feed between them.

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I'm guessing the loop gives much more flexibility  when fitting the parts  and  makes individual removal more practical. What year is the bike?.

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1963 year. I have banjos facing backwards on the old concentrics, I think after advice from NOC (quite possibly from Phil...) many years ago. But I see air bubbles in it sometimes, because the downdraft slope means the middle of the loop is higher than the ends. I think I'll try straight this time.

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Do you have to make a fine adjustment to the float level  to counteract the DD ?.  My experience with new plastic floats  led me to put the old brass one back in !!. I have some valve bodies  machined to change the fuel level.

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All I can say is I hope not. The design is actually quite clever. It is a circular float in a circular chamber, so as soon as it departs upwards from mid depth it should shut off.  So in theory I thing it shouldn't be sensitive to the angle.  They were of course standard fitment.

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Hi David,

On my 650 I have the pipe banjo's pointing back a bit - maybe a 30° angle or so. As Robert says, makes fitting so much easier - not just putting them on the carbs, but also accessing the pipe clips to tighten them.  Don't make it too long though as the pipe could pinch up on itself and stop the flow. As you are going 'rubber', make sure the pipe is to SAE J30 R9 spec as that is allegedly ethanol damage resistant up to E10. Go for a known brand too as there is some rubbish about that is supposedly to this spec.

BTW, I have no idea how they were done originally - ask 2 owners and you will get at least 3 opinions on what is correct.

As regards the float, if you go with a new Anal "StayUp" float, be aware that they can be "Stay Down" floats as well! I know I am not alone in having had issues with them.

On mine, all looked perfect when installed prior to fitting the cover, but when riding the fueling wasn't good. A check for float height showed fuel level was way too high.  My fix, for quickness, was to add a second gasket to the float chamber and all was well so I don't know what is 'wrong' on mine. As it worked and isn't leaking I have left it like that until I have the carbs off again. Others have spoken of casting flash and /or the pivot boss being wider than the original ones causing issues.

Hope that this helps,

George

 

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Well if you find  problems setting it up  you are welcome to try my needle bodies..  When Anna was making sense and referring to the 650 DD  Manxman ( what else!) she recommended  machining 10 thou off to give a better pick up.

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I have the correct hose from Surrey Cycles thanks. The spigots on the banjos are quite long. I wonder if it will even need clips. I can tell this could be a barrel of worms! 

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As the fuel is not under pressure you probably don't.  But some really neat clips look like you mean it and know what you are doing!!.

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David,

If the rubber softens (quite likely) even just a little bit you will have a fuel leak almost on top of your magneto....

If the resulting flames don't take the paint off the frame, engine plates etc, then the petrol almost certainly will.

They don't need to be jubilee clips - thin sprung wire loops will do the job perfectly well.

I know your bike doesn't need an MOT test, but if it did, the rules say that a fuel pipe that is insecure is a "Major Defect" and a  pipe that is insecure such that there is a risk of fire is a "Dangerous Defect".

When you sign the MOT exempt form, you are stating that the vehicle is roadworthy. 

I would hate to see your bike suffer damage that was easily preventable for not spending 50p - £1 on suitable clips

Best regards,

George,

 

Always best to use the proper fuel pipe clips, not Jubilee clips as they can cut into the rubber - especially the type where the threads cut right through the clips. 

It means you have to get the correct diameter clips of course as they don't have the adjustment range of the "Jubilee" type.

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Good words George..I think the aged CG125 propping up a fence outside just had hoses pushed on...I'll use clips. Fingers crossed they'll work out of the box.

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My 99  had a plastic fuel pipe from new with no clip at the banjo  ,it lasted for  over 60 years  and even coped with eth fuel .  I decided it was too hard and likely to fracture ,and replaced it with reinforced plastic.  The old  had to be sawed off. The new one has a clip , but I doubt it will survive  5 years  even with  only the occasional mistake of filling with eth fuel.  Keep checking your taps and pipes. 

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You can get the original ferrules in the UK and crimping tools on eBay from the US

Search for British Standard Fuel Line Ferrule Crimping Tool Triumph BSA Norton 

and 6 plated 1/4" BORE fuel PETROL PIPE CRIMPS FERRULES-BSA TRIUMPH NORTON English

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Thanks Steve. All so simple and yet the plot thickens...the bottom banjos need 3/8 pipe and I have a metre of 1/4".

 



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