cheap fuel pressure problem fix

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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blaster

cheap fuel pressure problem fix

Post by blaster »

i may have mentioned this before but the fuel pressure on all the weber equiped models can be easily adjusted. in the fuel return line there is a carburator main jet located about in the middle of the fuel line that is attached between the t-fitting and the fuel tank. it;s even in the parts catalog. now i have never had to do this because i switched to mikunis before i discovered the jet while inspecting the fuel lines so i don't know how much affect changing the jet will have but it's pretty obvious the intent of the design. i have looked through all the old tech notices i got from ducati and there was no mention of this even though the problem was known back then though that doesn't surprise me one bit. ducati can get a little cryptic sometimes. anyway, if anybody tries this or has already post the results, i would like to know. oh, i think the ss models have this jet too. blaster
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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: cheap fuel pressure problem fix

Post by ducinthebay »

Blaster,
I had heard this before, but since my bike was so badly bastardized, I could never confirm nor deny that it was true. Opening up that return line would surely help. I don't know why they thought they needed that much pressure to a carb with a float bowl. The simple fact of having a couple inches of head of pressure works for every bike I have ever seen. I have never run into a fuel starvation problem without the restrictor in place. Makes you wonder what problem they were trying to solve.

Maybe it was supposed to be in the feed line and not the return line.
I also don't know why a carbureted bike needs a fuel pump either.
Easy things to fix, but strange engineering.

Cheers,
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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ducapaso
paso grand pooh-bah
Posts: 1097
Joined: Sun Aug 01, 2004 12:00 am
model: 750 Paso
year: 1988
Location: siena, italy
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Re: cheap fuel pressure problem fix

Post by ducapaso »

ducinthebay wrote: Makes you wonder what problem they were trying to solve.

Maybe it was supposed to be in the feed line and not the return line.
I also don't know why a carbureted bike needs a fuel pump either.
Easy things to fix, but strange engineering.

Cheers,
Maybe they were tryiing the improve refilling of carb float after a long stanby, due to fuel evaporation.
I put my pressure regulator there, so that air bubbles can flow away through the carb itself
(you know, elder pasos had no return petcock in the fuel tank!)
have a nice ride, Nicola

Black "DUKE" 751582
ex...Red "smooth" 753349 :-(
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