750 Sport fuel lines routing

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
Post Reply
Desmo Tutu
Posts: 19
Joined: Mon Oct 24, 2016 8:21 am
model: 750 Sport
year: 1990
Location: Norway

750 Sport fuel lines routing

Post by Desmo Tutu »

Need some help with my 750 Sport I picked up in bits & boxes. The bike is soon to be completed, but I have a question about the fuel lines. The bike has the stock Weber.
Inside the tank there is a bit of fuel hose directly from the pump to the pipe going from the top too the fuel tap. So no internal filter. It seems a previous owner has mounted the fuel filter outside the tank, because there was a filter in one of the boxes. But how is the fuel line suppose to run?

My first thought is from the tap on the right side, in front of the rear shock, then around the left side of the rear cylinder, cross between the cylinders, through the Y-pipe to the Weber. Or does it run from tap, front of rear shock, then over the cylinder head either over or under the frame brace and down to the Y ?
I guess I can put a new filter somewhere between the tap and the Y.

Oh, and I need a seat cover if someone have a spare or know where to get one... :cool:
MatthiB
Posts: 12
Joined: Sun Dec 31, 2017 8:35 am
model: 900 SS
year: 1990
Location: Germany

Re: 750 Sport fuel lines routing

Post by MatthiB »

Hi Tutu,

I ran both lines, the one from the tap to Y and the return line from Y to the socket at the bottom of the tank over the cylinder head under the frame.
For a cleaner look that is.

Btw. make sure you have a smaller diameter hose for the return line.
It does not necesseraly have to be a (120) jet.
My Weber runs pretty good with a piece of 5mm hose inside the 8mm fuel line.

Cheers
Desmo Tutu
Posts: 19
Joined: Mon Oct 24, 2016 8:21 am
model: 750 Sport
year: 1990
Location: Norway

Re: 750 Sport fuel lines routing

Post by Desmo Tutu »

Thanks, I will try that route. When you say make sure not to run 8mm on return, is that if you don't have the restriction jet, or even if you have the jet?
I was going to replace all fuel lines with fresh 8mm fuel line. But you advice me to go 5-6mm on return line? Does this matter as long as i have the jet in the return line?
MatthiB
Posts: 12
Joined: Sun Dec 31, 2017 8:35 am
model: 900 SS
year: 1990
Location: Germany

Re: 750 Sport fuel lines routing

Post by MatthiB »

It's either or.
If you have a jet in the return line it's fine.
You're good to go with 8mm hoses for all three bits.
Desmo Tutu wrote:Thanks, I will try that route. When you say make sure not to run 8mm on return, is that if you don't have the restriction jet, or even if you have the jet?
I was going to replace all fuel lines with fresh 8mm fuel line. But you advice me to go 5-6mm on return line? Does this matter as long as i have the jet in the return line?
steveT2
Posts: 65
Joined: Thu May 05, 2016 7:37 am
model: 750 Sport
year: 1988
Location: UK

Re: 750 Sport fuel lines routing

Post by steveT2 »

Neither of my bikes as a jet or smaller hose on the return, both bikes run fine (750 sport and the 900 both with the Webber) is this a mod or standard.
MatthiB
Posts: 12
Joined: Sun Dec 31, 2017 8:35 am
model: 900 SS
year: 1990
Location: Germany

Re: 750 Sport fuel lines routing

Post by MatthiB »

Standard is a 120 jet in the return line.
But in my opininion that's too small.
Depending on the fuel pump pressure that could give too much pressure to the needle valve with the risk of overflooding the carb.

If your pressure system feeds the carb just enough to keep the fuel level OK at full gas with no restriktion in the return line - perfect,
steveT2
Posts: 65
Joined: Thu May 05, 2016 7:37 am
model: 750 Sport
year: 1988
Location: UK

Re: 750 Sport fuel lines routing

Post by steveT2 »

You have me thinking now, should i or shouldn't i .
User avatar
paso750
paso grand pooh-bah
Posts: 5503
Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 750 Sport fuel lines routing

Post by paso750 »

usually the jet was screwed into the Y piece. When the fuel hose is pulled off it would sometimes remain in the hose.
steveT2
Posts: 65
Joined: Thu May 05, 2016 7:37 am
model: 750 Sport
year: 1988
Location: UK

Re: 750 Sport fuel lines routing

Post by steveT2 »

Oh well..... I managed to squeeze some 5mm hose into the 8mm return hose, will see how it goes.
Desmo Tutu
Posts: 19
Joined: Mon Oct 24, 2016 8:21 am
model: 750 Sport
year: 1990
Location: Norway

Re: 750 Sport fuel lines routing

Post by Desmo Tutu »

What is the routing for the fuel tank breather pipe?
I have the european version, in case there is a US anti-smog version with some crazy piping... :cool:
User avatar
Antomonster
Posts: 7
Joined: Wed Aug 30, 2017 9:31 am
model: 750 Paso
year: 1990
Location: Spain

Re: 750 Sport fuel lines routing

Post by Antomonster »

Desmo Tutu wrote:What is the routing for the fuel tank breather pipe?
- https://www.stein-dinse.biz/eliste/?sid ... 28cb&lg=de :shock:
Post Reply