[Sack]

Hey Guys how are you?

Im a 30 years old German male living in the USA for 3.5 years now. I'm currently studying Computer Science.
My Ducati 900ss is my 4th bike know but my first italian Diva. I want to join the forum for technical troubleshooting and giving advices as far i can. I would say i have an average do it yourself level. I know the rules how carburetors and fuel injection works and I'm a trained electronic engineer.
My biggest project was to completely overhaul an 2000 BMW X5 to an facelift 2006 model. That took me about 2 years and i did everything starting with B like bodyworks over Drivetrain, engine and to I like interior. Also all Computerunits replaced and coded. So far, thats about me and my skills.

Anyways, my only question I'm having so far is, why is my 900ss running on only one cylinder in idle? i cleaned the carbs, starting, pilot and main jets. Also the channels behind the jets are clean and the Archangels too. When i have it in idle, i can remove the sparkplugconnector of cylinder one without any rpm change. when i remove cylinder 2 sparkplugconnector and the engine dies. I sprayed starting fluid in the carbs and cylinder one is firing then. also when i go up to about 1400 rpm, its starting. Did anybody have the same problem and has an idea what i could also try? the fuel/air mixture screw has been "adjusted" so its not closed and... yeah like i said... the carbs are cleaned and double-checked several times know. I sprayed brake cleaner into any single jet and air channel and its getting through with a nice steam to every point it should guide to.

Thanks in advance and enjoy your rest of the day.

Greetings

Sack

bought bike with mods and 16000 mls on it: Supertrap muffler
open Airfilter
Dynojet stage 2

 

[pat1098]

Welcome aboard Sack. Wilkommen.

Tell us which year model (welche Jahre) your SS is. I take it it is between '93 and '99?

These carburettors are difficult to get cleaned once they are blocked. Many are suffering this problem now at this age. I have had to dismantle and clean them more than once to sort them out. They also can develop a small crack in the carburettor diaphragm (under top lid).

The best solution is a set of Keihin FCRs, which improve your connection with the bike, as well as its performance. But they are not cheap..

You also need to check the electrical and charging circuits, as any weakness there can manifest as a weak idle. One cylinder will fail to fire if there is insufficient electrical charge to the coils. Make sure the battery is good.

You need a direct earth from the battery to the engine (as well as the stock indirect earth). And check the regulator output - it should read from 13V - 14.6V, no more - with the engine revving.

Also the stock coils (if your bike is between '93 and '99) are weak. Replacements from Dyna or Bosch (transformer-type) will help with starting and running at all revs.

Also make sure the valve clearances are set correctly, as these can also have that effect if they need adjustment.

Basically your bike needs a comprehensive service and tune, and new coils. This should sort your idle problem, and make your bike perform much better.

I hope this helps you get to enjoy your Ducati. With these issues resolved you will find it an excellent machine.

 

[Sack]

Thank you very much for your fast respond

Well its a 93 model. It has NGK Sparkplug connectors. What size or type of the Keihin FCR would i need for the Ducati? So you mean clean is not clean enough? But how will you know then when you are done without putting everything together just to take it apart again xD When they are that clean like mine, is there an Fuel ad that would take care of the last small "maybe" pieces during ride?

 

[Sack]

The ignition coils, from Bosch or Dyna are also many different types. any recommendation?

 

[pat1098]

I usually fitted Bosch Transformer coils, but the Dynas are a bit more compact. The supplier can tell you the most suitable model for your bike.
I developed a bracket for mounting the Bosch coils which used the original wiring unchanged, even though the coils had to sit outside of the igniters due to their size.
On the plug caps - you may have resistance-type plug caps, so you may not need R-type spark plugs. Take advice from an auto electrician as to which plugs are better for these plug caps.
You may benefit from 'hotter' plugs than recommended - 6s or 7s in NGK - with the stock coils. You should be able to run cooler plugs (8s) if you change the coils.

 

[pat1098]

As to the carburettor size - you can fit either 39mm or 41mm FCRs to the 900.
39mm are probably better for all-round road use, on a fairly stock bike, whereas the 41s are probably a bit better on the track, or with other engine work (valves, cams or 944 piston kit).

 

[Gunny Fitz]

Congrats !

That was my first Ducati as a matter of fact!
Welcome to the forum and congrats on an oldie but goodie for sure! There are so many things you can do with that bike since it still has carbs, etc.

I had a 944 kit installed with the bigger carbs as someone else stated here. 41mm Keihins to be exact. The stock suspension sucked so you can always replace that or have it set up for you. Without a doubt that thing pulled like a freight train with awesome torque! Enjoy it!

 

[Sack]

Problem solved

Hello everybody,

thanks for all the answers. Finally I solved the problem. The problem was the small gasket washer at the fuel mixture screw that is underneath the spring. At one carb it was missing. Now i replaced it and the bike runs great now. so no need of any carb replacement or anything else... maybe for now

Thanks again everybody for your help