I am starting to spend more time investigating problems than riding! After what began as a non-starting issue, my bike starts ok but will only run on one cylinder. When it has been running, and then stopped, I've noted that there is white smoke/vapour from the RH silencer, which means the rear/vertical head. Nothing from the other exhaust. Not sure what this indicates? Any advice on where to start troubleshooting? I presume a methodical check of the ignition system components would make sense.
It's either not getting fuel, or not getting spark. Easy enough to check. Turn it over a bit, then stop, remove plugs and check if they are wet. While you're there check colour of the plugs for burn. Could it just need a new set? They are cheap enough. Blocked jets on carb could be issue, meaning no fuel. But, yes could be a number of things, but start with the simple first. I'm assuming the compression is OK.
Plugs as pictured, after running for a few mins. Neither look particularly 'wet' though. Exhaust popping even at idle. Increased the revs gently to 3000, kept the throttle position, and the revs then appeared to return to idle. Compression, never checked by me. I need to buy a gauge.
Many thanks. In which case you cannot assume that the gasses or white vapour seen coming out of one can is immediately attributable to a particular cylinder.
I would replace definitely those plugs anyway. Whether is is related to the issue or not, at least start with a matching pair!
identify which cylinder is not firing then swap the plugs over to se if the misfire changes cylinder that would indicate faulty spark plug the one on the right seems a darker colour to the other but as said not a matching pair so could be a different heat range and not burn as clean
Thanks, I actually fitted a brand new pair of NGK DCPR8E today and the problem is still there. The conclusion of the popping is that there is unburnt fuel in the cylinder. Ignition circuit seems to check out. I have another set of carbs, so the next thoughts are to do a straight swap and see whether that resolves.
Sounds like we’ve had similar issues. When I get mine back from the bike whisperer, I’ll let you know what fixed it. I’m assuming carb rebuild.
Took mine repeatedly to Mcr Ducati with similar issues and didn’t get anywhere It took an old school mechanic, who has knowledge and patience with old school engineering to set it up correctly Runs sweetly now.
The popping of unburnt fuel you say, is that popping in the exhaust? If so it could be an igniter box issue, put a strobe light on and check they are both advancing, they jump to full advance around 1600 rpm, if you have one stuck at 6 degree that will cause the popping in the exhaust. Ask me how I know
ok before you change the carbs try swapping the ht leads over and see if it makes a difference also you could swap the coils over from one to the other to see if misfire changes from one cylinder to the other if you have a multi meter you could check the ohms resistance range of the ht leads also check if any loose wires at coils etc hopefully not the ignition pickups themselfs and check for air leaks around the intake manifolds could be an idea to check valve clearances as well think I would check that lot before taking the carbs off
Great you got it sorted but that is a really sad indictment on the competence of supposedly time served mechanics working for a franchised dealership.
If plug caps have been changed, or removed and refitted, it’s always worth trimming/cutting off the last half inch of the HT lead so that you are certain of having a good, solid connection to the wire core of the lead. Screwing caps on and off the HT leads will eventually break the delicate core strands over time reducing the contact and thereby the spark at the plug.
Thanks all, some great tips there. Unfortunately I'd already committed to the carb swap, but ran out of time/light today so will finish tmrw. Needed to fettle the area underneath the carbs anyway. Will report back ASAP.
thats a good point on the leads and caps was meaning in comment to swap the lead and cap as one as most leads now are cap and lead moulded as one modern technoligy and all ha
Update Looks like it was the carbs, swapped over with another set. Maybe it was some cr4p in one of the main jets. Road tested and all good. Can't thank you all enough for the great info, really appreciate it. I've enjoyed the process, and learning how everything hooks together. These are beautiful bikes to work on.
