Paso not starting: no fuel to carbs!

lceriani · Post by **lceriani** » Fri Jun 03, 2005 9:09 am

After a period of inactivity I can't start my Paso.
Engine is a M900 with a pair of Mikuni BDST 38 and a fuel pump from a Ducati Monster. The battery is fully charged, the starting motor runs well and the spark plug sparkles. It seems that no fuel arrives to the carbs!
I checked fuel tap and pipes and they are not obstructed. In the carbs the float valve is not blocked. The valve diaphgram and the needle appear not damaged.
When I run the starting motor, the fuel don’t reach the float chamber: it goes ahead and back into the pipe that connects the fuel pump to the carbs. I tried to disconnect the fuel pump, letting the carbs inhale from a bowl kept over the float chamber level, but there is no depression…
I don’t know what to check else… any suggestion?

Thanx,
LC

Post by **Skins** » Fri Jun 03, 2005 9:28 am

Is the fuel tank breathing OK? Have you tried starting her with the fuel tank filler cap loose?

lceriani · Post by **lceriani** » Fri Jun 03, 2005 9:40 am

Yes, the fuel tank is ok...

Post by **Skins** » Fri Jun 03, 2005 8:14 pm

I know you say the problem is fuel not getting to the carbs, Luca, but I have read a common problem after inactivity is blocked fuel passages in the carbs, caused by deposits from the petrol, and that it may be neccessary to clean out the passages and jets.

But if fuel is not getting to the carbs, perhaps the fuelpump is faulty or the fuel system needs to be primed. Have you checked for a bad connection in the power supply to the pump?

Gwenadu · Post by **Gwenadu** » Fri Jun 03, 2005 8:48 pm

i have have the same difficulties with my paso. fuel evaporated from the carbs after a week without use. I use "start pilot" to help.(not the best for the engine...). I will re-install the electric pump because the Monster pump works by depression from the inlet pipes, so if the engine doesn't start immediately...
Iceriani, on the monster there is no return pipe to the tank so that makes perhaps little more pressure to the carbs.

ducapaso · Post by **ducapaso** » Sun Jun 05, 2005 2:27 pm

Ciao Ice!
Ancora non parte?
Allora a mali estremi, estremi rimedi!
prova a spruzzare un po' di benzina direttamente nell'airbox mentre fai girare il motore: va benissimo un erogatore di quelli per pulire i vetri in casa (volgarmente detti "spruzzini") un paio di colpi e stai a vedere cosa succede... se il motore reagisce, allora è colpa dei carburatori intasati, se non c'è nessun risultato, prova a dare la colpa alle candele, qualche volta la patina oleosa che lascia la benzina evaporando fa scaricare a massa la scintilla.
Have a nice ride
P.S: this tip will be soon aviable in english, I apologize for the disase.
Nicola

lceriani · Post by **lceriani** » Tue Jun 07, 2005 9:43 am

Effectively the fuel pump was faulty (probably due to fuel deposits). I cleared it, I filled the pipes and the float chamber with fuel and it started in a few seconds.

Thanx to everybody for the tips!

LC

PS for Gwenadu: effectively the monster fuel pump don't have a return pipe to the tank, so I inserted a Y connector after the exit pipe of the pump, and then one pipe goes to the carbs and the other one to the fuel tank… I don’t know it is perfect, but it seems to work!