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 Post subject: Re: Fuel pump
PostPosted: Fri Apr 19, 2013 3:52 pm 
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paso grand pooh-bah
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Location: SF Bay Area
model: 750 Sport
year: 1990
Nice simple drawing. One change I would make, maybe minor, is to feed pressure into the base of the "T" instead of one of the top fitting. This ensures even pressure to both the carbs and the return line. As you have it, there will be slightly higher pressure to the carbs. (Slightly)

For what it's worth, my pump in my Sport runs full speed all the time with a healthy stream through the return line all the time.

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 Post subject: Re: Fuel pump
PostPosted: Fri Apr 19, 2013 7:10 pm 
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Location: Nottingham, UK
model: 906 Paso
year: 1989
When I purchased a replacement 'T' piece from my local Weber outlet, well it was more of a 'Y' piece the base tube was wide and the two tails were narrow so there is a right and wrong to this. Naturally the wider tube takes its feed from the pump.

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 Post subject: Re: Fuel pump
PostPosted: Fri Apr 19, 2013 9:35 pm 
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paso grand pooh-bah
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Location: Newzealand
model: 906 Paso
year: 1990
JWilliam wrote:
Mc tool wrote:
R U kidding me ? Did the laws of physics suddenly change ? Think about what you just posted :banghead yeah , beats the crap outa me how they won the war :D


What are you talking about? Do I need to add idiot arrows too? Fuel out of tank to pump then splits between return pipe and regulator. The whole point being the fuel flow is never stopped to the pump and the carby gets no more than 3psi. Try this any other way eg. Regulator after fuel pump & before 'T' piece and you are looking at burnt out exhaust valves.


BOLLOCKS!!!!!! ( BIG _ucken hairy ones at that !) For a start you don't run a return line with a regulator ,and having the T after the regulator makes the presence of the regulator completely pointless ! burnt valves ?? I guess if your stupid enough to keep flogging an engine ( only just ) running that lean you may eventually do some damage ...... so you burnt your valves did ya :D :D :D :D :D :D :D :D :D

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 Post subject: Re: Fuel pump
PostPosted: Fri Apr 19, 2013 11:30 pm 
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paso grand pooh-bah
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
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idiot is as idiot does Forest as in can't see the trees :wacko:



Hamish, there are times when a return line is the preferred method depending of course on the type of regulator used. My point was the drawing is not the proper way to go about it, In fact the drawing is the least effective way to use the Holley type regulator. Might as well just put a jet in the line and sacrifice one more hard to get fuel pump or sack the weber for some rookkie dukie mikuni :banghead: oops!, There I go voiceing my 2cs again

bad higgy bad :beer:

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 Post subject: Re: Fuel pump
PostPosted: Sun Apr 21, 2013 4:36 am 
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paso grand pooh-bah
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Location: Newzealand
model: 906 Paso
year: 1990
Aw , I was looking forward to your discenting opinion ( must have been one hell of a pissup ) and any how I have spent the last two whole days fixing ( -ucking about with ) my Paso , mmmmm might even post some pix later

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 Post subject: Re: Fuel pump
PostPosted: Mon Apr 22, 2013 9:42 pm 
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Location: Nottingham, UK
model: 906 Paso
year: 1989
No there are no burnt valves in my 906 and I also have a quick release fuel pipe connector (image corrected - page 2) on the return line that is quite restrictive - but no return line? I kept the return line so that the fuel pump cant be stopped and consequently overloaded (ie. a 'full carb' means no fuel flow). The fuel pump fairly chucks fuel out, it must cycle a full tank in less than 10 minutes therefore I dont envisage fuel starvation with my arrangement. I'd have to say its a tricky subject and one that could do with measurement before statement, I'm not saying right or wrong here although my 906 has had no running problems associated with a lean mixture and 'reflow-out' to fuel tank is a common arrangement for regulators
Regulator is a Pro-Flow regulator - Weber part CR9412

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Last edited by JWilliam on Tue Apr 23, 2013 12:03 pm, edited 1 time in total.

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 Post subject: Re: Fuel pump
PostPosted: Mon Apr 22, 2013 11:32 pm 
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paso grand pooh-bah
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
JWilliam wrote:
No there are no burnt valves in my 906 and I also have a quick release fuel pipe connector (not illustrated - sorry) on the return line that is quite restrictive - but no return line? I kept the return line so that the fuel pump cant be stopped and consequently overloaded (ie. a 'full carb' means no fuel flow). The fuel pump fairly chucks fuel out, it must cycle a full tank in less than 10 minutes therefore I dont envisage fuel starvation with my arrangement. I'd have to say its a tricky subject and one that could do with measurement before statement, I'm not saying right or wrong here although my 906 has had no running problems associated with a lean mixture and 'reflow-out' to fuel tank is a common arrangement for regulators
Regulator is a Pro-Flow regulator - Weber part CR9412



So basically you have no clue one way or the other :idea:

Obvious to some of us..........going by the drawing :fart:

yes reflow out the regulator is common way of doing things
Still your drawing is wrong in many ways and no help at all to someone asking questions


restricting the return line makes a huge difference...Guess you forgot to illustrate that minor detail.....


Everyone is here to help including you..What is obvious to many of us is not to most of the newbies here

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Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: Fuel pump
PostPosted: Tue Apr 23, 2013 12:35 pm 
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Location: Nottingham, UK
model: 906 Paso
year: 1989
Drawing is revised - see page 2 of this thread

What I have done is follow the initial design by Ducati. If the fuel pump was mechanically driven by a cam off the engine then its output would approximate 'rpm vs fuel pressure' and a regulator without reflow would be ideal. The fuel pump is electric and is always running at max output, Ducati know this and placed a reflow pipe to avoid overloading the pump at low engine rpm. If the electric fuel pump is forced to run at low output it will draw excess current from the DC bus and it is likely to burn out and fail. I was concerned about modifying and because I often have the tank off I thought a Quick Release Coupling on the return line would be convenient, although it is hardly a free-flow it better suits the application since there is no way the carb will be under pressured (similar to a jet in the return line). When I turn on the ignition I can hear the fuel pump reduce bpm after the carb is primed and looking at the reflow rate, it is still flowing but not at the rate it was before the Quick Release Coupling was fitted. It is a good compromise and I don't see what other way it can be done while still remaining faithful to Ducati's original concerns. Apologies if each post isn't entirely informative, there is a lot of info to convey and I don't actually work for Ducati.

Image

If you aren't sure of the results then watch the Youtube video link below... You can tell the carburation is adequate. The engine idles, pulls away, responds to throttle and reaches high rpm without any flat spots and can maintain high rpm. If it was too rich it wouldn't tick over and would be prone to stalling. Too lean, there would be flat spots and it wouldn't reach nor would it maintain high rpm. Don't need a dyno-room or banks of gauges to tell me that.

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