V7Sport Fuel Cruciform |
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Glawster
Senior Member Joined: 14 Sep 2015 Location: Cheltenham Status: Offline Points: 896 |
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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.
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1970 Guzzi V7 Ambassador
1955 Guzzi Falcone Sport 2021 BMW R1250R 1998 Cagiva Gran Canyon |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Would that not mean you lose any reserve in the tank?
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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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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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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Glawster
Senior Member Joined: 14 Sep 2015 Location: Cheltenham Status: Offline Points: 896 |
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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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1970 Guzzi V7 Ambassador
1955 Guzzi Falcone Sport 2021 BMW R1250R 1998 Cagiva Gran Canyon |
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George S
Senior Member Joined: 31 Mar 2018 Location: Essex UK Status: Offline Points: 643 |
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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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George
1994 Nevada 1962 Lightweight ducati Bevel Single Son's 1990 1000S to borrow any time |
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Barry
Senior Member Joined: 02 Mar 2015 Location: Oxford Status: Offline Points: 2811 |
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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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Ken-Guzzibear
Moderator Group Joined: 13 May 2014 Location: Sileby Leics Status: Offline Points: 9454 |
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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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The Older i Get, The Better I Was
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ranton_rambler
Senior Member Joined: 13 Feb 2015 Location: Stafford Status: Offline Points: 1147 |
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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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iansoady
Senior Member Joined: 23 Jul 2017 Location: Redditch Status: Offline Points: 2402 |
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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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Ian
1952 Norton ES2 1986 Honda XBR500 1958-ish Greeves/Triumph in progress |
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jpc
Senior Member Joined: 06 Oct 2016 Location: Belgium Status: Offline Points: 651 |
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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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Glawster
Senior Member Joined: 14 Sep 2015 Location: Cheltenham Status: Offline Points: 896 |
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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.
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1970 Guzzi V7 Ambassador
1955 Guzzi Falcone Sport 2021 BMW R1250R 1998 Cagiva Gran Canyon |
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