Red Paso blues

[Josh]

Hi All,
Great site. Been lurking for a few weeks. Resurrecting the '88 Paso a buddy of mine gave me eight years ago.
Cleaned the carbs, the petcock screen, replaced the hoses, took out the restrictor in the fuel line (return), did the coil upgrade for better voltage (red line to the positive terminal of the battery), new plugs, cleaned stuff - yada yada.
So now when I try to start it, two twists of the throttle, it fires up, then dies no matter what I do to the throttle. If I leave the fuel pump on gas gushes out of the rear cylinder's carb. So can I leave it turned off. Do I need it?
In spite of this post I am actually not a bad backyard mechanic. This has me stumped and I can't bring the bike in or afford to send the carbs out for rebuild. Anyone have the correct float level adjustment info?
Sorry to be a pain, but I really need to start riding.
Thanks,
Josh

[Desmo_Demon]

So now when I try to start it, two twists of the throttle, it fires up, then dies no matter what I do to the throttle. If I leave the fuel pump on gas gushes out of the rear cylinder's carb. So can I leave it turned off. Do I need it?

Unplug the fuel pump. It is not needed. It sounds like the one carb has the float needle not seating, and with the fuel pump running, you are probably flooding out the engine. See if unplugging the fuel pump helps. After this, we can do some more troubleshooting.

What carbs do you have on the bike? Dellortos? Mikunis?

[Josh]

Can't believe I left that out.
DellOrtos 36 phf. My buddy put them on way back when.
I rode the bike for a bit when I first got it, but it was stalling, backfiring, hard to keep going in stop and go in semi-suburbs where I ride.
Thanks for the info re: fuel pump. Can I plug the bypass return line and just route directly to carbs?
How do you set the float level? Do you think the carb will still flood w/out the pressure from the pump?

[Desmo_Demon]

Thanks for the info re: fuel pump. Can I plug the bypass return line and just route directly to carbs?

I left the return hooked up and bypassed the fuel pump. This is a diagram of my fuel line...

How do you set the float level? Do you think the carb will still flood w/out the pressure from the pump?

I'd just disconnect the pump. It simply isn't needed. For setting the float level, I don't remember where I found the specs, but I found them online somewhere. I'll see if I have an e-copy of it, if not, I may have to scan if out of my three-ring binder of Paso information that I collected while rebuilding my bike.

[Desmo_Demon]

Here's a link to the functions and set-up of Dellorto carbs...

http://www.ducatimeccanica.com/dellorto ... lorto.html

Here's the page specifically for setting the floats....

http://www.ducatimeccanica.com/dellorto ... o_3_2.html

Carburetor
float position mm

PHBG 16.5 + 15.5
PHBL 24.5 + 23.5
PHBH 24.5 + 23.5
PHBE 18.5 + 17.5
PHF 18.5 + 17.5
PHM 18.5 + 17.5

[jcslocum]

The Dell's will gravity feed just fine. No pump needed. the reurn line isn't needed either so you can leave that off as well. Once the plugs are fouled, you need new ones. Get the carbs sorted and change the plugs. You will need to take them apart and use carb cleaner and air peressue to fully clean them out. Old fuel makes a very hard lacquer that plugs stuff up. Change the fuel filter too. Drain the tank and run fresh fuel, get some "Seafoam" and mix it with the fuel. It's an excellent cleaner.

It should start up and run just fine.

[Josh]

Thanks for all the help. I'll get some time this weekend to do the work. I'll let you know how it turns out.
You guys are terrific.