Evening all It's been a while since I posted on here, hope you're all doing well? Looking for some help here. I am fortunate to have a beautiful half-faired 1992 900SS, which I rebuilt from a pile of bits four years ago. Since the rebuild it has run like a charm once some early tickover issues were sorted. I've done about 3500 miles on it since the rebuild. including two trackdays at Cadwell. I have another coming up in a few weeks time. Last night I was out for a quick blast. After a bit of hard acceleration, overtaking a couple of cars - one of which some sort of red Porsche - and cruising at a "decent" speed I felt a misfire or two, I slowed up a bit then continued, but it misfired all the more, and eventually lost power and coasted to a stop (embarrassingly the two cars then came trundling past. Sigh). It felt like it had run out of fuel. Popped the cap up, it was low but there was enough fuel in it. Span it over a few times, a bit of choke and it fired up again. I rode home the few miles at a sedate pace with no issues. Here's what I know: The tank is in decent nick and I have no reason to suspect rust in the tank blocking the fuel offtake. I can hear the fuel pump running. The fuel lines aren't kinked or pinched that I can see (I have recently had the tank up - see below) I run it on Super Unleaded (has JE high comp pistons in it) I have pulled both plugs and they both look OK, light tan/grey. They are the OEM recommended Champion RA6HC. They came in the pile of bits and are of unknown age. It has what appears to be the original coils and ignition on it. Oh and the metal plug caps. Last week I can back after a week away and found the battery flat as a dab. it's a 3-year old Motobatt and has always been healthy with good cranking. I don't think I did but it's possible that I had left the ignition in the "park" position and drained it by accident. If I didn't do that then I don't know what happened to cause this. It was showing 1.7 volts and by rights should have been toast, but amazingly, after 48 hours + on charge, my Accumate seems to have recovered it to the point where it is up above 13 volts and spinning the starter again like a good 'un. So my questions: it has to be fuel or spark, right? What are the symptoms of plug failure or coil failure? Plugs are cheap so it would seem to be a no-brainer to change them anyway, given that I don't know their age. If coils are suspect I'd be up for a set of the ExactFit coils (does Exige still do a deal on here for members?). What about the ignition? Are these prone to failure? Could the recent battery issues by a cause? As I say, battery voltage appears to be healthy now (I tested it when I got back ad it was 12.9 volts ish. The reg/rec is Ducati OEM. If that had failed then I wold be experiencing charging issues, right, not flat battery when been stood for a while issues. Anything else I should check? I will pull the fuel filter out this weekend to check all is well in there. Thanks in advance as always for your help. Cheers James
Hi James - whole can of worms you've included there, and could be so many of them plus more, so will go with first thought (just for starters) and that is a blocked fuel tank breather pipe and/or blocked one-way valve on same circuit. Even this is more persistent/easily noticeable on a full tank rather than an empty one, which i believe yours was more like, but it's easy to check this one at least. You can work through the usual suspects one by one after this - symptoms are also similar to initial stages of an ignition pick-up breaking down but this usually still remains trying to run on one cylinder.
Thanks Chris, good shout on the tank breather/one way valve. I’ll check that. I had a Multistrada 1000DS that used to stall when the tank dropped to quarter full because of a blocked breather… Many thanks
I forgot to add - as tanks are getting older, even the steel tube leaving the tank can block (usually with rust) giving the same result. Even a tank in good condition can have this happen. It's unlikely, but if it is blocked solid you might have to resort to a drill bit inserted in chuck (for better grip) but hand turned.
OK, so fairly sure it's not a fuel issue: tank breather / one way valve is not blocked (interestingly, I can blow air through it both ways? Maybe it's there to stop petrol flowing out in the event that the bike lands rubber side up). The tea bag looks clear. The fuel filter looks OK and was new when I rebuilt it, though the bike has done 4,000 miles since, and the Haynes says replace every 3,000. I'll put that on the list, but for now I think unlikely as a cause of the symptoms experienced (unless anyone tells me different - it is a genuine Ducati part). The fuel pump runs OK, though intermittent failure can't be ruled out I guess. So, now assuming it's electrical. The battery is still fit and starting like a good un, so I'm ruling that out. The connections are tight. The way it failed felt like both cylinders shutting down together, rather than missing on one, which makes me think not coils or pick ups or plugs, though I can't be sure. I've ordered a new set of plugs but they're not here yet. Going to have a run up and down the road and see if it does it again...
Hi Reading your post fuel starvation seems the most likely cause of your problem, not saying it isn’t ignition though. Check your flexible fuel pipes inside the tank as these have been known to rupture and loose a lot of fuel flow also there’s a fuel filter at the carb inlet, check it or better still remove it, it looks like a sock if it’s still there.
Thanks bumpstart, I don't recall seeing that particular filter when I put it back together, but then, they're easy to miss. I'll take a look and see if it's there. I did take it for a run on the weekend, a similar route to where it cut out on me last time, though perhaps not quite as exuberantly. Didn't miss a beat so who knows...?
The combination of poor running and a flattening battery suggests to me that your rec/reg is on the way out. It is acting as a parasitic load on your battery and causing poor running….I just had this problem with my 900ss. Check google for how to test for parasitic load.
I wonder how many components in your fuel system (tank to cylinder) are thirty years old? Even the tiniest item like a filter could be blocked or simply perished. I have renewed everything on my 1982 MHR, especially rubber, plastic, carb gaskets and had a thorough clean. I think it is too much to expect these items to last that long and it is not as if they are expensive to replace.
