fuel problem.

jahrasti

Hi all,

So I had the bike out on the weekend to go to this sea side town called Ragaln, it has the best coffee.

The main reason was to try and diagnose a problem as the bike had been running funny.

On low constant throttle (4k rpm range) on highway speeds the bike will bog and loose power and sound like its running off throttle. When I open the throttle it will sputter and kick off aging running properly.

However at higher rpm it is fine without the hesitation.

Pump is quite new although I haven't completed a flow test yet, I would doubt that the injectors have ever been cleaned though. I am contemplating if they are not flowing correctly.

What do you guys think?

duck2

What bike is it? What's the setup? Has it got open pipes and not had the fuel remapped?
Clean air filter,fresh fuel,new fuel filter, new plugs/caps,valve clearances correct?
There's loads to investigate,I'd start with the cheapest (fuel,plugs,and filter) and work my way through it,BUT if it needs a new ecu chip then that has to be addressed!(easy fix😱)

jahrasti

So now I am confusssed.

I had my bike at the track this week and I was able to highlight some more issues.

Bear with me whilst I try and explain it, I am not massively familiar with the intricacies of the Ducati engine unlike race bikes I've previously owned.

Firstly the problem arises at infrequent times.

Whilst going through say the infield consisting of multiple turns, the bike would run fine even under a short burst of WOT.

However long sweepers and straights at WOT it was weird, it was like the clutch was slipping as engine speed would increase by 1000 to 1500 and then settle back down. Okay I thought clutch is gone. Trouble is at one point it happened twice in one gear.

The next lap is when the surging happened. The bike would surge and stutter at pretty much any point at the circuit.

The bike would accelerate and then surge before going into compression and then accelerate and so on.

If I stopped it idled and revved fine but once leaving again same problem. However if the bike sat for say a session it would run fine and then go through the same cycle.

I didn't bring my bloody tools so ended up coming home as there was no need to carry on and destroy the bike.

What do the people in the know think? I hope you can understand my gibberish 😉.

griff851

Bummer. Could be fuel filter, but first I'd disconnect plugs and reconnect. ECU, TPS and timing sensors, relays etc. Vibration has a habit of causing weird running. After that multimeter time.

griff851

Just remembered one more possibility. It's a nasty. We had a bike that somebody had worked on. The flywheel retaining screws had come loose. As the fly wheel was flopping around it ran weird. Initially it was ok, and the customer took it. Then it started hunting. Then really crap throttle response. It started and idled ok which was confusing. After checking all resistances and I mean all, there was only thing left which of coarse I wasn't expecting. Low and behold a wobbly flywheel and scrap marks on the alt cover.

jahrasti

griff851 wroteJust remembered on more possibility. It's a nasty. We had a bike that somebody had worked on. The flywheel retaining screws had come loose. As the fly wheel was flopping around it ran weird. Initially it was ok, and the customer took it. Then it started hunting. Then really crap throttle response. It started and idled ok which was confusing. After checking all resistances and I mean all, there was only thing left which of coarse I wasn't expecting. Low and behold a wobbly flywheel and scrap marks on the alt cover.

Awesome thanks for the input. I am going over the electrical side as per your suggestion and if no luck I will check the fly wheel.

I appreciate your help!

Twigs

I assume you've checked the plugs and checked or replaced fuel filter?
Had similar issues not too long ago with my 888 (see fuel issues? thread)
I ended up cleaning the tank out and replacing the fuel filter.
Pulled the spark plugs out and the electrodes were very white indicating lean running due to fuel starvation.
Runs fine since changing the filter but I'm thinking about getting a new fuel pump just to be sure.
Good luck
Mauro

griff851

Electrical and change the fuel filter. Worry about nasty things when all the easy things are exhausted. Checking sensor resistance and coils is easy. Just look for obvious differences. Good thing about having two of stuff. And as a bonus when you find the fault you feel good about yourself.

jahrasti

All sorted

So I thought I would finally get around to replying as I have sorted the problem.

I changed the fuel filter but the one on it appeared fine (looks can always be deceiving), but what the actual problem was an air lock.

The hose in the tank from the filter to the tank was shot and air was being sucked in via the cracked hoseclip via the filter end and causing air to enter the system.

I have road tested and tried to induce the fault but all ran fine so I will see how I go.

griff851

Nice one. Glad you got it sorted.