A few things to check:

- I don't know wether you replaced the carbs or just used pieces and bits from the carbs you bought. Keep in mind that you can't mix stock parts with Dynojet parts (a lot of these bikes are equiped with a Dynojet-kit). Make sure your carbs have Dynojet or stock parts and not a mix of the two.

-Make sure the carbs you bought came from a 600SS and not a 900SS. A 900 uses different jets and needles. Even more: European carbs use different jets then USA-carbs...

- Don't forget the sync the carbs!!!

- Don't forget to check the fuel level in the bowls!!

-Make sure all breather lines are open (if not you probably would have problems synchronising the carbs.

-Don't assume that the 1,5 turn out is correct. You can use that as a start point but very often they have to be screwed out further then 1,5 turn.

- Read this. Seriously; read it!!

And on top of that; it won't hurt to check the timing of the ignition.

And last but not least: wait for some advice from the more experienced members on this forum. And thank them for that.

Good luck!!

 

A few things to check:

- I don't know wether you replaced the carbs or just used pieces and bits from the carbs you bought. Keep in mind that you can't mix stock parts with Dynojet parts (a lot of these bikes are equiped with a Dynojet-kit). Make sure your carbs have Dynojet or stock parts and not a mix of the two.

-Make sure the carbs you bought came from a 600SS and not a 900SS. A 900 uses different jets and needles. Even more: European carbs use different jets then USA-carbs...

- Don't forget the sync the carbs!!!

- Don't forget to check the fuel level in the bowls!!

-Make sure all breather lines are open (if not you probably would have problems synchronising the carbs.

-Don't assume that the 1,5 turn out is correct. You can use that as a start point but very often they have to be screwed out further then 1,5 turn.

- Read this. Seriously; read it!!

And on top of that; it won't hurt to check the timing of the ignition.

And last but not least: wait for some advice from the more experienced members on this forum. And thank them for that.

Good luck!!

Superb! Thank you for your suggestions.

I did use the Needles from the original carb that was on the bike as the eBay one came with what looked like dynojet needles as you suggesed, however the jets looked right, but they are definitely worth a revisit.

Everything I've read so far on syncing the carbs requires the bike to be running, which is certainly a problem at the moment. Certainly the butterflies seem to move in unison, but synching the fuel/air mixture without the bike running - is that possible?

I have replaced the timing belts and the positions looked right, though I've not re-checked the tension since doing them, so I guess that's worth another look too.

Time to strip her down again then...

Thanks a million for the guidance, it is just what I needed!

 

Have you removed the float covers and checked for contamination? Are they clean? Sounds like one cylinder is not getting fuel and one is getting too much. I would start with disassembly of both carbs and squirting carb cleaner through all the small holes. Do not spray the rubber diaphragms on the slides as this will damage the rubber.
check the float needles and seats for contamination and proper operation( sticking or leaking). Then I would take a hard look at the internal rubber gaskets and replace any that are cracked or damaged.

 

Have you removed the float covers and checked for contamination? Are they clean? Sounds like one cylinder is not getting fuel and one is getting too much. I would start with disassembly of both carbs and squirting carb cleaner through all the small holes. Do not spray the rubber diaphragms on the slides as this will damage the rubber.
check the float needles and seats for contamination and proper operation( sticking or leaking). Then I would take a hard look at the internal rubber gaskets and replace any that are cracked or damaged.

I've not done this since fitting the carbs, as I only just get the whole thing back together I was hoping to avoid having to strip it right back, as the carbs and especially the accelerator cables were a real pain to fit, but I guess you are correct, they need looking at. Certainly everything looked fine when I fitted them, but they could be blocked or I was wondering if a jet came loose would it have this effect perhaps too.
Anyway thank you, I'll get the allen keys out and make a start...

 

Are you using the enrichener to start the bike?

Yes it sounds as 1 carb is getting too much fuel so pursue that first, is the enrichener stuck on on that carb only?
If you start the bike and while running you see the throttle slide is not opening or not closing on either?

I do not know the 600ss as they did not sell them here in the US but 1.5 turns out sounds too lean to me. Belter has much more experience on these so he may know otherwise.

Basics=
what carbs? are they 600 carbs?
What jets? dynojet, factory,mikuni,ebc may all meter different amounts of fuel even if they have the same number stamped on them. Stick to one only if possible.
Jet kit needles or stock?
Original pilot jet or increased size?

The fact you have one off makes it more likely something is wrong with one carb and NOT a base jetting setup. Running a enrichener WILL blacken a plug some as the amount of fuel dumped in is large to start a cold motor. If you add more fuel because of something off then you can quickly flood it.

 

Are you using the enrichener to start the bike?

Yes it sounds as 1 carb is getting too much fuel so pursue that first, is the enrichener stuck on on that carb only?
If you start the bike and while running you see the throttle slide is not opening or not closing on either?

I do not know the 600ss as they did not sell them here in the US but 1.5 turns out sounds too lean to me. Belter has much more experience on these so he may know otherwise.

Basics=
what carbs? are they 600 carbs?
What jets? dynojet, factory,mikuni,ebc may all meter different amounts of fuel even if they have the same number stamped on them. Stick to one only if possible.
Jet kit needles or stock?
Original pilot jet or increased size?

The fact you have one off makes it more likely something is wrong with one carb and NOT a base jetting setup. Running a enrichener WILL blacken a plug some as the amount of fuel dumped in is large to start a cold motor. If you add more fuel because of something off then you can quickly flood it.

Yes I have been using the enrichener/choke to start the engine as it had only started when cold, so if that (and the excess fuel) in that side of the carbs explains the blackening that is good.

And yes they are 600 carbs.

I think after taking the air filter off yesterday I may have a partial solution. The non-starting it turns out was because once of the cables from the pickup coils was loose, and actually just fell off when I started taking it apart, so I think that will solve the starting issue, and then I (hopefully) just need to go back adjusting the idle and the fuel/air mix on both carbs to get the mix right!

Thank you for your response and helping me to see the wood for the trees!

 

mixing jets & or needles between stock & an aftermarker jet kit -you are asking for a nightmare. I suggest you take the carbs off --determine that they are the correct part number for your 600SS--(If not you need to get the correct carbs)--If they are the correct carbs take them apart and clean them properly---Rebuild with a carb kit replacing all O-rings, & gaskets. --Now do one of 2 things--replace all jets & needles with stock parts--OR replace all jets & needles with an aftermarket jet kit and adjust to which ever one you chose. --Otherwise you are going to be chasing your arse and driving yourself crazy. --But you have to start with a known baseline.

 

OK great, thank you, and you are right I should start from scratch certainly on the jets, as that's really the only unknown for me, the carbs themselves are the correct ones, and I've dismantled, cleaned and re-furbed them already with a kit, the needles were from my original carb, it's only the jets that I'm not 100% sure about.

However I've now solved the starting issue, as that was a major pain, as being unable to check anything running was really difficult, so with that and all the additional advice on this page I'm pretty sure I can get this resolved now.

Thank you very much!

 

If you do end up going thru the carbs again, the balance can be baseline set off the bike by cranking in the idle speed screw enough to use a small drill bit shank or other pin as a butterfly feeler gauge ,set both sides for equal drag, then back the idle speed screw back out to nearly close the butterfllies. This should be close enough to run and get a balance gauge on it.
Good luck,
Jim

 

Superb, that's a great bit of advice thank you!

 

check the pilot jet on the side that had the clean plug. i would go 3 turns on the idle mix screws. wind the idle stop up until it idles, then try to get it down.

 

Perfect! Thank you. I was worried about starting too rich, but I had started with both on 3 turns out, so I'm glad to know that I wasn't necessarily flooding the bike by doing that - I didn't know how sensitive these things were.

Think I have the starting issue solved anyway, and that turned out it was because once of the cables from the pickup coils was loose, so that was what I needed - now I can happily get back to working on fine tuning the rest.

Thank you!

 

Thanks for all the responses, as a new Ducati owner and a very new joiner to this forum all the replies and advice have been very welcome.

I have some way to go to get this fixed, but I feel confident of what I need to do now.

Firstly as I started dismantling the bike to take the carbs off (which having done it twice before is not a job I relish as those accelerator cables are a real pain to get back on!) - I spotted one of the cables from the pickup coils was loose - the red one on the left side of the pic below - this seems to have been the cause of the non-starting, or intermittent non-starting, as once reconnected the bike fired right up multiple times with no bother.

So then back to the spark plugs - I will go back to my original plan of increasing the idle to 1200 RPM to stop it constantly stalling, and then use the Gunson Colortune (which seems a great tool for getting the air/fuel mix right if anyone hasn't got one) to adjust the mixture to get both cylinders mixing the fuel and air correctly.

If that doesn't work as planned then I will go down the route of removing and re-building the carbs (again) with new jets which I know are right for the bike as that is the only unknown now I think.

It does seem the wiring on these old Ducati's is not the best, which I think is somewhat typical of Italian vehicles of this age, so I'm sure this won't be the last time they cause me concern.

So thanks to all who responded, I really didn't expect quite so much great advice or so quickly. This is a superb forum that I'd been getting advice from as a non-member since I got the bike, and I'm now very happy to be signed up and participating too!

 

"It does seem the wiring on these old Ducati's is not the best, which I think is somewhat typical of Italian vehicles of this age, so I'm sure this won't be the last time they cause me concern. "

So your regulator rectifier if a Ducati electronica is not great quality but easily swapped to one that is. Some have the headlight pigtail melt due to corrosion so clean and tighten the connectors and you should have no issues. Other than that I do NOT see any electrical issues so if you are finding issues this is more prior owner induced than a "italian electrics" thing.

I have worked on them since new and put your wiring harness up against one from any brand made today. Find and fix things messed up and then simply maintain and do no harm and it should serve you well for many more years.

If you have your carbs apart look for makers marks on the jets, Mikuni have their stamp on oem parts. Dynojet does not nor do Chinese knock offs from cheap rebuild kits. Post a picture of your needles and we may be able to identify them if they have no markings.

 

"It does seem the wiring on these old Ducati's is not the best, which I think is somewhat typical of Italian vehicles of this age, so I'm sure this won't be the last time they cause me concern. "

So your regulator rectifier if a Ducati electronica is not great quality but easily swapped to one that is. Some have the headlight pigtail melt due to corrosion so clean and tighten the connectors and you should have no issues. Other than that I do NOT see any electrical issues so if you are finding issues this is more prior owner induced than a "italian electrics" thing.

I have worked on them since new and put your wiring harness up against one from any brand made today. Find and fix things messed up and then simply maintain and do no harm and it should serve you well for many more years.

If you have your carbs apart look for makers marks on the jets, Mikuni have their stamp on oem parts. Dynojet does not nor do Chinese knock offs from cheap rebuild kits. Post a picture of your needles and we may be able to identify them if they have no markings.

Ah that is really good to hear. I've tested the regulator rectifier and that all seems good, as with most everything else seems to be working well at the moment, so fingers crossed it all keeps working OK.
Thank you.

 

I have the same question for a 600ss of '93: which jets do I have to order for the revision of the Mikunis ?