I’m trying to find out how to get a Ducati single to start running again. Fuel in tank, taps open, 12.5V in the battery, plug sparking outside the cylinder, smell of petrol from the cylinder. Kicks over but won’t fire up. Puzzled!
Worked before- generally starting first or second kick with about one third choke- but I have left it for a couple of months and no joy now. Recently took the carb apart- a Dellorto- cleaned it all out and put it back together with new seals. Seemed to run better after that, pulling better above 4000rpm.
Generally was running rich. Does anyone know which way to turn the mixture screw to lean it? Clockwise gives 4 turns until it’s all the way in. but is in or out richer or leaner? and does too rich prevent an engine starting?
Fuel and a spark - sounds like everything you need.
Have you done anything at all since the bike was last running?
I get this problem occasionaly with my racer - but that’s generally when I’ve forgotten to take the cover off the carb bellmouth!!!
Might be worth checking that the faces of the points are clean and that the timing’s correct.
maybe check for leaks between the carb and cylinder head (cracks in rubber mounting if it’s rubber mounted).
Don’t rush into changing everything though - it’s too easy to loose track of the original problem by changing the timing, carb settings, plug, coil, condenser, points, etc, etc.
I posted this reply earlier, but it’s not showing - well, not on my 'puter anyways; so here it again …
A few ideas, some of which I’m sure you’ve tried …
Fit a new plug (and clean the plug lead and make sure it’s fitting into the coil well).
Check the carb control cables, i.e. make sure that neither the enricher nor the slide is hanging up.
Did you re-set the float height? If too high, you can have trouble starting.
If you have a PHF carb, it is important that the drilling which provides air for the idle circuit is clear - with today’s fuels, it often gets blocked as the lighter elements in the fuel evaporates. Then the bike won’t start. I’ve had this happen in 6 weeks of non-use on my Laverda Corsa. Carb cleaner can help, ultrasonic bath is best.
Strictly speaking, the idle screw doesn’t either weaken or enrichen. Instead, it adjusts the amount of air/fuel mixture, with the mixture strength being pre-determined - see the Dell’Orto manual posted here filejumbo.com/Download/E9A7373D7DA0566F.
But that said: out is more mixture, in is less. I½ turns out should be your starting point.
Did the bike idle before?
Btw, in general, the ‘choke’ (it’s not a choke, but I’m sure you know this) should be either on or off - in fact, the later twins used just such a control.
Hi, sometimes when an engine has been idle for a while the lube drains from around the piston rings, and so lowering the compression, pumping more petrol into the cylinder makes thing worse, try removing the spark plug, injecting some oil into the cylinder turn over the engine several times, clean the spark plug, refitt and try again.
Many thanks for all the advice. In the end I gave up and took the bike over to Brian Silver at Moto Mariana. He’s got it all sorted and discovered. amongst other things, that it had the main jet for a 450- hence the permanent flooding, etc, etc.
Going well now and have just ridden the 75 miles home- my navigational error- down the M25 with a huge grin on my face.
