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V7Sport Fuel Cruciform

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Glawster View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Glawster Quote  Post ReplyReply Direct Link To This Post Topic: V7Sport Fuel Cruciform
    Posted: 21 Nov 2018 at 09:11
I think this applies to all Tonti bikes with VHB carbs, but maybe also Le Mans as well.
I find that fuel supply system with the cruciform connector under the airbox a real pain.  There's an additional 2 fuel lines and an additional 4 line ends to seal, all potentially under attack from Ethanol.  Also it's an area of limited space and not easy to fit in.
I'm minded to just put a fuel line from each tap directly to the carb at that side of the tank and not connect them.  I don't see a practical issue with this.  Has anyone any feedback?  Of course there could be a fuel starvation issue on full throttle with a 45 degree lean angle and low level of fuel in the tank...but realistically this isn't going to happen.  Interested in your thoughts.

DSC_0861 by Derek Wardell, on Flickr
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 09:19
Would that not mean you lose any reserve in the tank?
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 09:25
I agree that the cruciform is a pain. On my V7 Special (1971) I've changed the single spigot fuel/carb banjos for the twin spigot type. So, one hose from each tap to each carb,then a balance hose carb to carb. This was the practice of Triumph,Norton and your old Laverda SF Derek. Run on one tap then you still have a reserve facility.
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Glawster View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Glawster Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 09:45
Both my taps have a reserve position so I don't think this would be a problem.  I agree it's good practice to have a balance pipe and Ducati bevel twins also use this method with the twin spigot banjos.  Maybe I'll give it a try without the balance pipe and see how it works.
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George S View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote George S Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 10:03
My Nevada carbs feed  as Glawster mentioned " balance pipe with the twin spigot banjos."
Set up this way by Moto Guzzi
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Barry Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 10:57
If you go the balance line route, surely you're only cutting out one (of 4) lines?!

Granted it *might* be easier to work with than the cruciform setup - albeit on the sinistra carb, the twin spigot will still be 'behind' the carb body - so maybe it's worthwhile for that benefit alone. Report back, Derek!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 12:33
Someone tried this a long while ago, i remember it not working, guzzi rarely add stuff for fun, to get rid of this you tend to need a balance pipe. The reserves are both taps but when you take out the fuel taps every bike i have done this on the rh reserve was higher than left SO i guess the bike splutters, usually rhs first flip right to reserve , when it splutters, after 20 ish miles the left up you then really really need fuel ......

As far as i am aware the balance pipe helps with fuel flow especially under acceleration ...Every twin on carbs seems to have a balance pipe ...my Norton did every Guzzi has , i guess the cross piece is a cheaper option than the dual banjo joint. As always your bike your choice 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 12:49
My 850GT has a balance pipe but it's done with a T-piece in each side. So even more joints but gives a bit more choice on where to put everything. Loops are a bit more spacious under the back of the tank anyway.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 15:51
I've just fitted a cheap plastic X piece from ebay. No ethanol problems so far but it's only been in there for a year.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 16:23
As Ken said, they rarely fit anything for no reason...

My understanding is that the cross-feed ensures that both carbs are starved simultaneously when reaching reserve. If it were not the case, you might just notice a loss of performance, keep the throttle open a minute too long, and risk holing the piston on the starved side. Makes sense.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Glawster Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2018 at 17:34
OK guys, point taken, I've plumbed it in as before.  Actually using new tubing (nice and flexible) and clips it wasn't so bad.  And the V7 Sport only has a kind of empty rubber boot, not a proper air filter.  This boot can be squashed up to get it into place.
So we're all connected up, better see if it runs ok with the new Gilardoni piston / cylinder kits and refurbished carbs.  Fill the carbs from my temporary "fuel tank" and thankfully first hit on the button and she's up and running.

DSC_0864 by Derek Wardell, on Flickr

DSC_0868 by Derek Wardell, on Flickr
1970 Guzzi V7 Ambassador
1955 Guzzi Falcone Sport
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