Hi to you all - I haven't got a Paso yet, but it isn't for the want of trying, just missed a 750 non-runner about 4 months ago. I do have above though, which you know shares quite a few bits.
My problem is that I haven't managed to get engine running yet, despite rifling through absolutely all the usual suspects.

My symptoms are:- on churning to start engine fires immediately but it's a backfire as though timing is too advanced (but it isn't). Occasionally it fires conventionally but i've stopped trying now as the regular kicking-back is not going to do the starter and sprag any good.

Just to let you know this is quite a baffling one - starter churn speed is good, both compressions are good (150 p.s.i.), am getting a regular spark on both plugs (stronger since I cleaned plugs and earths), belts are good and timed correctly, ignition is single point pick-up like some Paso's and gap is correct, On start churn, say around 3-500 rpm, connected strobe shows spark aligns with TDC on both cylinders (I mark them on the clutch!), I am using fresh fuel, Weber 44 has been overhauled recently, and I have also checked jets - have also been using Bradex Easystart occasionally to confirm no starvation (coughs is the same with or without).
I am starting to scratch my head as this is probably a 'can't see the wood for the trees' moment - can anyone help with any fresh suggestions? - I also have Digiplex 442A as per 907, but as spark seems consistent I could be barking up the wrong spruce.
Also, can anyone confirm that timing is correct to be aligned at TDC when engine is turning that slowly? - I looked at ignition advance graph and it seems quite reasonable.
I have already corresponded with Gerhard, who has an obvious Paso Passion! Many Thanks in anticipation.

What spark plugs are you using?

Fresh petrol in tank?
Good fuel filter?
Adequate amount of petrol flowing to carbs, sparks getting wet?
Running/starting before this normal?

Hi Higgy and Tamburinifan - Plugs are correct NGK '8's and yes, plugs are at least getting wet. Unfortunately I can't comment on how it came to 'not run' as bought it like this. I checked the two airscrews today both wound in and sadly someone has 'leaned' on one and partially stripped thread.. Have set both mixture screws to two turns out. As I said, I am baffled at the moment. Just had a hunch while typing and I think I might be onto a winner... I have depleted sense of smell due to a virus - when I emptied the crankcase of oil to check alternator nut etc, I thought it was a little thin - i've just gone and stuck me snoz right in it, and it made my eyes water! The only other thing I could think of that would explain the early firing symptom (other than being advanced) was if the throttle was cranked open too wide.. (or in my case flooding possibly due to hardened gum on float needle valve) Being a downdraught the overflow pipe (if there is one?) wouldn't get much of a chance would it? I'll get back to you after I put cover back on etc. Thank you for taking the trouble you two.
Regards

have you tried swapping the plug cables ?

it sounds like you are firing the cilinders with the plug cables fitted the other way around.

Usually the coils are Marked "V" for VERTICAL, "O" for Horizontal, so it is easy to check if they are correct, however sometimes it happensa that the wiring coming from the Digiplex/Modules to the coils has been swapped around by mistake...

Fuel in the oil would certainly give you problems if the float valve is stuck open,on the other hand if it was stuck closed oncce you drain bowl it wouldn't fire at all. Stuck floats are not uncommon on any carb, and with the weber especially it would go right down the cylinders

Thanks Angelics, but no, I centre pop the two TDC's on the flywheel side and then put an 'H' and a 'V' next to them - easier to see the strobe light there as well. I'm hoping it's the flooding that's the culprit but won't be able to test it until i refit cover (had to order a new nose bearing so am changing g/change sleeve bearing and oil seal as well - came to about a tenner from Ducati UK!

If you are spraying starting fluid(ether) in the engine and its not running or turning over you have a spark problem.

Thanks for your input duc 907,could you narrow it down a bit?

I was just thinking about the Xed plug wires too !. The only thing I can offer is that my paso runs like a bag of hairy arseholes without the airbox cover. Im thinking that these duke motors will quiet happily start and run on one good pot so what ever is stopping yours is common to both pots . Is the digiplex getting enough voltage , especially while cranking ?Have you checked cam timing with a degree wheel, or just the timing marks provided ? If the latter is the idle shaft correctly timed where its geared to the crank ? . Fuel in the oil would indicate ( to me anyhow ) that its getting heaps of fuel its just not able to burn it.The fact that your regularly getting backfires sez its getting fuel , spark and seeing as how its got good( ish ) compression..... it sounds like a timing issue , assuming that the fuel is fresh ( just coverin my ass here ).
Lookin forward to hearing what it is , good luck

Thank you Mctool - that is another check to do (Digiplex voltage) and I will check accuracy of cam timing just for the pleasure of finding out. I can't report anymore yet as haven't got service bits in post yet (plus just come out of hospital )
Will certainly post soon. All the Best

I meant to say that the timing of the idler shaft would only be an issue if it had been apart since last going. Sorry to hear you have been crook, ( I know the feeling )

latest update :- All back together after checking nuts at both ends of crank, so tried a 'dry carb' start attempt with Bradex only and result is almost the same, i.e. big kickback.. While stripped, I took the trouble to double check/triple check all of ignition and valve timing and everything is correct. There was one difference - engine did fire about 3 times before petering out on one occasion. Allthough I was getting pretty consistent readings whilst using strobe I think I will have another look at the Digiplex unit and check out the vacuum sensing input..

Been thinking about this ( as you do )This is starting to sound a bit ( lot ) like an issue I had on my 900ss.Twas a bitch to start from cold , starter straining away and the spit back and stop dead thing ( I remember feeling real sorry for that starter clutch, and if you had asked me then I would have said it was turning over ok ). Usually I had to jump start it off a car battery , It fair lept into life then. To make life easy I connected the bike end of the jumper leads to the solenoid and the footpeg bracket. So any how I bought a new battery and f--- me it was no better..... new brushes in the starter ... still no better.It was a Faulty battery earth cable , which I had cunningly bypassed by hooking the earth ( jumper ) lead to the foot peg , had I connected it to the battery earth ...... I reckon you should try jump starting it off another battery , hooked up like I did so as to bypass as much of the original cables as poss.If you do have a faulty cable you can bet the crook terminal will get hot too .
There is a recent thread somewhere here about just this thing advising of a kit to cure such ills on a paso/907 and the fact that my SS came out 10 years after the paso still with the same fault ( cheap shit, undersize cables and terminations )Made me replace all the cables and terminals with bigger ones, end of problem.