rich running

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Duccout
Posts: 1285
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: rich running

Postby Duccout » Thu May 07, 2020 4:28 pm

I wonder if Sudco have a manifold that allows the Mikuni to fit closer to the inlet flange?

Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

Re: rich running

Postby Scottish888 » Thu May 07, 2020 8:48 pm

Thanks Ducout,

I have some 40mm id rad hose with bends in it that could do the trick.
After fitting the new Mikuni, it made no difference, tried various needle positions where it seemed to run a bit sharper on the lowest setting but still nothing after 4500 rpm. I am going to re fit the Dellorto and mod the spring, at least everything fits with that carb.
I can now say I have eliminated all the fuel side so that leave the sparks, it runs clean to 3700, gets rougher then really rough at 4500, then nothing.
Plug, lead and cap are all new, I think the spark looks very weak but clearly good enough in start condition where it is most likely to foul.
What tests can be done to check if this is the coil/transducer or the coil output from the engine case?
Looks like this could be another ornamental single :(

Jordan
Posts: 1380
Joined: Fri Dec 24, 2010 11:29 am

Re: rich running

Postby Jordan » Thu May 07, 2020 9:44 pm

Fitting an air cleaner to a widecase single can be a pain due to frame obstruction.
I'm using a foam type that has a built-in angle, just works.
I had an AJS single that was even worse for clearance, where the oil tank was the impediment.
The solution for it was a slender, sheet metal round box that was attached directly to the screwed inlet of the carburettor, and used all the available space. The challenge was to not restrict air flow too much.
Metal sheet is thinner than rubber.

To confirm an ignition fault, if available, temporarily install a points plate, standard HT coil etc.

graeme
Posts: 938
Joined: Sun Mar 25, 2012 12:00 am
Location: Tasmania Australia

Re: rich running

Postby graeme » Thu May 07, 2020 11:20 pm

I used a DNA offset air cleaner that fits and clears the frame (250 frame)
These won’t fit with a 450 frame without mods

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Duccout
Posts: 1285
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: rich running

Postby Duccout » Fri May 08, 2020 6:54 am

To my shame, I know nothing about electrics, but I do know that your ignition system is almost half a century old, and that over time magnetism and insulation break down. I know that is is a PITA, but probably the only way to be sure is to fit a modern ignition system ( or perhaps a coil and contact breaker, although this may cost about the same).

Any problem with an engine that won't run right is a toss-up between ignition and carb issues, and I'm sure that we have all been in the same boat, but you have eliminated the carb as the item at fault. Years ago my Velocette Clubman decided to not rev properly and I spent ages chasing my tail, but in the end it was a weak spark from a faulty magneto armature.

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: rich running

Postby ranton_rambler » Fri May 08, 2020 7:28 am

First thing I was told in my vehicle fettling youth - 90% of problems are ignition....

Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

misfiring

Postby Scottish888 » Fri May 08, 2020 1:28 pm

Ok, Dellorto back on and bike starts fine and runs ok at low revs.
After reading about misfiring on this forum, I decided to check battery voltage and outputs, all good. New gel battery was holding 6.48v, started the bike up and checked various connections at the regulator, 7.49v at tickover, dropping to 6.48v if lights are turned on. So, it looks like the charging side is functioning well.
As the bike starts fine, does that mean the ignition winding coil is working ok? is it possible it could break down at higher revs? how can this be tested?
If that side is ok, it only leaves the transducer/coil? does anyone have a test procedure for this? the Haynes manual is useless in regards to these type of problem.
I have ruled out the whole fuel side, it only leaves spark. I set the timing statically and it can't be that far out that it can still start but not run over 4000.
Even up to 4000 it is not clean, holding it around 3000, it still stumbles but would drive and pull ok at those revs.
Apart from buying all brand new is there anything else I can test?
which wires coming from the engine can I use to check the resistance if the ignition coil inside?, what values should I expect? it must be eiehter the red or yellows.
I fould a site about Morinis which discusses the Ducati eletronica fitted and some repair tips, not sure how much I can use for my Ducati.
http://www.motomoriniclub.nl/tech.html#repair
Someone mentioned fitting points, what parts would I need? I guess a standard 6 volt coil could be used? that way I can eliminate the transducer/coil.

Regards

Duccout
Posts: 1285
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: rich running

Postby Duccout » Fri May 08, 2020 2:24 pm

I'm no expert whatsoever, but could the ignition not be advancing? Could it be running retarded all the time? Many years ago when my 900 Ducati was a few months old, it developed a problem similar to yours; I hired the Ducati strobe tool, which checks that the ignition is advancing properly, and found that one cylinder was not advancing. Further investigation showed that one of the pick-ups was touching the rotor. Resetting the pick-ups cured it.

I know that there is no similarity between the systems, but it would be really good If you could strobe yours to check the advance. What about the air gap between the rotor and pick-up? Have you rechecked it?

As for changing to points, you would need the complete backplate, with points and condenser, advance and regard mechanism, plus a 6v coil. The backplate should be easily available from eBay, but by the time you have bought all the bits it may be cheaper to fit an Electrex World kit.

Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

Re: rich running

Postby Scottish888 » Fri May 08, 2020 3:30 pm

Hi Duccout,

I tried my strobe but it hardly picks up anything, works on all other bikes and cars but this is the first 6 volt I tried with it. I had to connect it to a 12v battery source but just got intermitant flashes so useless. I run the bike and adjusted the ign backplate by hand at higher revs, it was best exactly where I had it statically timed (at least for TDC anyway)
I could not see any timing marks cast into the cover behind the hex plug on the clutch case, Haynes manual said it should be there.
Advancing it by hand as it was running did not improve anything, so the electronic advance may be ok.
Just taken it for another run, it will now rev to about 5000, this time I opened the throttle wide, it just gasped then some firing on and off but with the bike getting slower, when I close the throttle it will pick up at 5000 rmp and run ok, as soon as I try going over, nothing, close the gas and it picks up. Done the same with the Mikuni.
I may not have set the ign back exactly as this time it was popping and backfiring on the over run, never done that before so the timing has had a small effect, maybe another 500 rpm but with popping on over run.
Forgetting this is a Ducati single, does that add up to any particular issue?


Regards

George
Posts: 385
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: rich running

Postby George » Fri May 08, 2020 5:23 pm

Common causes of pop on overrun are leaks in exhaust system, unburnt fuel in exhaust caused by either to rich or timing out. Possible that exhaust valve not fully closing. Would also be worth checking valve timing correct. Good luck
George Essex UK


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