Bike cuts out under load?

[ducatilover]

from a pic i have seen, "pri" is between "on" and "res". switch it to "pri" and go for a test ride. this has been suggested before though.

edit: is your fuel pump run with vacuum or electric?

My thoughts exactly.

To my knowledge they didn't have a fuel pump, just gravity feed, so I'd rule that out (going to laugh and cry if it does have a pump though...)

[Lus7]

My thoughts exactly.

To my knowledge they didn't have a fuel pump, just gravity feed, so I'd rule that out (going to laugh and cry if it does have a pump though...)

http://i.imgur.com/Budda.png
It's got a fuel pump. You'll be laughing because it makes it easier to fix.. right?

[Harry the Barstard]

Best thread in ages.... some funny shit!

Hope you get it working mate, well after a few more pages anyway.

[ducatilover]

Yay, another spanner in the works!

In that case, I am going to assume there's no vacuum line to the tap and it has a vacuum operated pump?
I'll go to google and look in a second.

Now, it shouldn't need a vac pump unless the fuel pick up in the tank is sitting lower than the carb float/bowl.
You should be able to bypass it.

First things first, check the condition of all the hoses to the pump, if you find an electrical plug I shall yet again laugh and cry.

[Lus7]

The diagram that I linked from the service manual says that there is a vacume line connected to the fuel tap
No electrical cables on the fuel pump, but there are a few plugged into the carb. checking the state of the fuel lines atm.

reakon it would be worth just replacing all the lines tomorrow with some standard fuel lines?

[ducatilover]

I'd expect there to be an overflow or return line from the carbs.
Replace the lines, but I wouldn't be surprised if you had a shagged pump

[Lus7]

i see, know of any way I can test to see if that's the issue?

[ducatilover]

Carry that little clear tube around.
When the bike cuts out, jump off (well, stop first) and check how much fuel comes out the carb bowl like you did before.
If it's significantly less, or much more, than it's a fuel pump issue.
Alternatively, you may be able to get a tee fitting and bypass the fuel pump and ride it.

[Lus7]

lol seems a little weird to have a fuel pump if you can bypass it.

I'm curious as to how this pump works, it's got no cables running to it so i'm not sure what actually powers the pump

[Lelitu]

then it's vaccuum powered

there will be at least 3 hoses going from it, one to the tank, one to the carb bowls, one to either an inlet manifold, or elsewhere on the carb

that last one is a vaccuum line, it works because it's airtight, and when the engine is running, the intake manifold/carb sucks the air out of the line, that powers the pump.

[Lus7]

Ok, so after reading the service manual's instructions on how to test if the fuel pump is working, I have determined it's ALL GOOD.
Got the fuel pump -> carb hose connected it to a jar. turned the bike on and fuel flowed out which suggests that the fuel pump is fine

damn, what next?

[Lus7]

So If the fuel pump relies on the vacuum tube to work and the fuel pump works, then the vacuum tube must be fine right. right?

[ducatilover]

When it cuts out, check the fuel level with your hose.
What I'd do is;
Make a mark on the bottom of the tank and hold the clear hose to that mark, take note of the fuel level.
Then do the same thing when the bike cuts out, this way you can see if the fuel level is dropping or raising.
If it's lower then there's a fuel restriction, if it's higher, your carb float needles are sad.
If it's no different?
Then we're back to step one and I'd still say clean carbs and replace fuel filter.
Then we'll look for electrical gremlins.

[ducatilover]

So If the fuel pump relies on the vacuum tube to work and the fuel pump works, then the vacuum tube must be fine right. right?

The vacuum tube could be fine.
It may still work, but not flow as much as the engine needs if it's split.
If it's soft, it'll close up and stop vacuum supply to the pump.
So, replace it just for peace of mind

[mellowyellow]

No electrical cables on the fuel pump, but there are a few plugged into the carb.

they wouldn't have fitted anti-desiling solinoids would they? surely not
that would be funny.
those are a bastard to diagnose without replaceing and would be controled by the CDI unit. check the electrical conectors for dirt and moisture