Hi, brought my '97 917 Biposto out from winter store last month and although she fired up and ticked-over fine, on running her up the road she started to miss-fire at sporadic moments, then run on one cylinder for a bit, then revving her would be fine, then miss-fire, until she would stall at tick over. Always started again on the button, would tick over for a bit but then miss-fire a bit. There seemed no pattern to the erratic running. First step I thought was to drain all old petrol, change the fuel filter and put some fresh fuel in. After an age getting the parts and getting the fuel pump back in the tank with that O-ring(!**$@&%**) , the bike still runs as badly as before. So what to check or replace next? She sat most of last year without running in the garage but has always run fine up until this spring. Last full service was about 3000 miles/3 years ago with cambelt change and did oil service last year. Any ideas?
commiserations arbman - so many things it could be but to start - did you check the internal fuel tank hoses for splits as this is a popular 'fault' that happens producing similar symptoms to that described.
Fresh plugs would be the second item to change, plus its always worth running an injection cleaning additive if with fresh fuel if the bike has been standing for a while. Modern fuels have so many crappy additives that cause gung and varnish to collect. My 900 ss carbs are as we speak being ultrasonically cleaned cos of Shit fuel!
Yep, will get some new plugs Monday and try them. Is there an injection cleaning additive to recommend? I've got some basic stuff from Halfords that I use in my Kipor generator and petrol camping stoves as they are always blocking up but not sure if ideal for Ducati carbs. Fuel lines in tank looked ok from basic inspection. Now they've been mentioned as a possible problem I wished I'd looked at them more thoroughly as the thought of removing and replacing the pump and that O-ring again is off-putting.
you can normally tell from looking carefully into the tank (torch only obviously) while it's running and particularly when you try and raise the revs as you will see the fuel 'thrashing about' noticeably if the split is large. It woudn't hurt to start routinely checking and cleaning all ignition-related connectors. Not entirely unrelated - have you checked your generator to reg yellow wire run (plus connector plug) across the engine yet? - even this can cause similar symptoms but usually accompanied by low cranking speed and burning smell.
Run bike while looking in tank - there's a fair amount of petrol seeming to be sprayed around at the top by the filler cap. Petrol level is very low but I'm surprised to see any petrol squirting around by the pipes and filter - should there be any at all or is it ok to have petrol squirting around the tops? Does it at tickover and when revved.
Sounds like it may be split. Petrol drips down from up under the rear lip of the filler cap. Guess I'm gonna have to remove pump assembly and check pipe thoroughly.
I had exactly the same thing happen to me on a 916. Turned out to be a crack in the plug lead boot that goes down inside the cylinder head . The symptoms were the same as you describe. To determine if this is the problem with your bike simply wrap the plug boots with black electrical tape and reinstall. If the bike runs fine replace both plug boots with new ones. Good luck
Have you got a return pipe from the carbs? If so, it will be sploshing fuel back in from high up near the front....at least it does on the carbed Ess-esses.... AL
AL - it's injected.. late reply to post #6 - it sounds as though there's a good chance you have a split pipe andas it's such a common failure considering age then it's worth checking.. It means injection fuel pressure is a fraction of what it should be so even idling will be laboured.
Yeah, I know Chris, but some injected engines have a return relief.......as for the 916, I don't have a clue! AL
Yes, there is a return pipe back into tank - even though it is injection I'm guessing a return pipe must return petrol? I wonder - Has anyone with a 916/996/748 ever looked in their tank whilst engine is running/idling to see if petrol comes back in through return pipe?
I'll try billd's test tomorrow to check spark plug caps, then wait to see if anyone knows if petrol returning to 916 tank is normal before I start to remove the fuel pump. It took me ages to get that O-ring and pump back in and seated right - don't fancy it again if I don't have too. By the way the only way I got pump back in was to set up a jig to draw the pump unit back in a fraction at a time - YouTube clip here if it helps anyone...relevant bit at 9m 55s..
the split pipe problem is a common occurrence - a return pipe causing described problem?.. over to you AL, i'm done here. http://www.ukmonster.co.uk/monster/showthread.php?t=45990 see post #22 ^ ^
No good asking me.......it was just a thought............if he has a return pipe, then it could be a split pressure pipe or the return just sploshing in....
Petrol does return, the fuel feed system is a loop (which the injectors are in) around which the fuel is constantly pumped and there is a regulator on the return so that fuel should be in the loop at a constant pressure but the excess (there is always some unless there isn't enough pressure) returns to the tank and can be seen splashing around in there. A split line between pump, filter and out line can mean there isn't enough pressure and this will cause fuel starvation, especially at higher RPM, a blocked filter can also cause similar problems. But what you described sounds like an electrical issue to me.
the return pipe does just that but will not cause turbulence in tank when revs are raised as it's only returning excess fuel surplus to requirement - i.e. at idle. a blocked filter rarely causes enough starvation to prevent idle from my experience plus he's replaced it anyway.
I've not got a clue about Ducati fuel systems but fuel returns don't usually spray fuel at the top of the tank especially around the filler cap.
