Well somethings not right. I have just bought a 97 Ducati 900SS which has sat for a long time and only started occasionally. Only done a few hundred miles since 2006. When I picked it up the fuel had been turned off as the previous owner mentioned occasionally the carbs would leak fuel even though he had replaced the needle valves. First job then was to replace the timing belts. Easy enough I have done them before so lined the marks up, took the belts off then next day put new genuine belts back on. Turned over by hand on the back wheel no issue slowly at first then spun probably 20 full rotations. It was late so left it until the next day, it started but was popping and back firing through the exhaust so turned it off thinking I had done something wrong. Checked the timing marks and all correct. Even got my son to double check and he agrees all marks line up as per the manual and also some marks made by a previous change line up. But it still doesn’t start just occasionally coughs or backfires. Obviously I suspect the cam timing but I guess it could be fuelling as the fuel was off for so long and for a reason. Going to swap plugs today and change the oil but any other suggestions welcome. Pretty sure the engine wasn’t turned with the belts off but if I didn’t know/think better i would say it is 180 degrees out…
With the timing marks all lined up, it can't be 180 degrees out, unless I'm missing something. If the carbs have leaked previously, then the float needle perhaps has crud, preventing them from closing properly and flooding the engine. If it has Sat for so long, I would suggest getting the carbs off and properly clean them out, with carb cleaner and compressed air, to make sure there's no muck, grit or oil fuel that's sat and blocked Airways. It certainly sounds like you've done the belts correctly. If it hasn't been used much, I'd strip the carbs. Sounds like that's part, if not all of your problem. I have FCRs on mine, and it was running great last year. Put it off the road and filled the tank and carbs with fresh fuel, with a stabiliser in it. Ran with a hesitation at higher revs recently. Now bearing in mind it ran fine last year, I suspected carbs, took them off and cleaned them out, now running sweet. My point being, that even after a few months of not running and stabaliser, the carbs clearly got gummed up. If yours has sat for years, think of what may lurk inside, preventing proper fuelling, and therefore could well be exactly what's causing the problems. Changing the belts, doesn't affect anything timing wise if you've lined it all up right.
When you changed the belts did you have any of the ignition system apart? Coils, ignition boxes, plug leads? If the plug leads or the connectors to the ignition boxes have got swapped you will see similar symptoms.
as above plus several other possibilities. Even a small amount of water in carb float bowl(s) will display similar symptoms.
Thanks all, simplest things first, changed the plugs and would you believe it fired straight up and runs great. I wouldn’t have believed a bad plug (or two) would have caused the bike not to start and backfire and a bit of a coincidence that it happened after changing the belts but there you go. All back together and running. It’s a bit tatty cosmetically but for £2k I want expecting much and intend to get all of the paintwork done. Need to read up on cleaning the engine cases which are pretty furry at the moment.
