1990 750 Paso Running on One Cylinder?

**Dave-M** · 02 Nov 07, 03:02 PM

My 1990 750 Paso had decided to run on the rear cylinder only front cylinder is dead as a dodo, so i checked for spark at plug and there is a brilliant bright blue spark but the plug looked dry - no fuel to the cylinder so had a look at the weber carb and there was quite a lot of rust particles in the float bowl

so i remove the carb and stripped it and used compressed air to blow through the various jets & air ways then i rebuilt the carb and refitted it, i rigged up a remote fuel tank suspended above the bike put some fuel in and started the motor and it ran on both cylinders

a result me thinks. well now i need to know how many turns out the air/mixture screws need to be so i can set the carburation so if any of you guy's can help with advice on settings for the weber it would be a big help.

thanks in advance
Dave.

**stevel** · 02 Nov 07, 07:21 PM

dave/ If it's a twin carb set-up (?) could you note the settings on the good carb and copy them over? bet you learnt from that experience!?

**Dave-M** · 02 Nov 07, 08:10 PM

It's one of them twin choke weber carbs -- bl**dy awful thing is one unit not separate carbs so i cant do as you recomend. think i will have to get a set of Mikuni's and throw the weber in the bin....

Dave.

**stevel** · 02 Nov 07, 08:42 PM

Dave....any help on ducatipaso.org?

**paso** · 02 Nov 07, 10:21 PM

Definately have a look on ducatipaso.org just make sure you log in you will get access to the downloads section which includes workshop manual etc . And dont throw the weber away they can be made to work well

**Dave-M** · 03 Nov 07, 06:52 AM

Thanks i am a member of ducatipaso.org but never give it a thought to look there

. any way went and had a look and it seems that to get the weber carb to perfom better i need to do some alterations to the jetting and fit a fuel regulator and set it to 2.75 psi.
mods to jets are
idle jets =060
idle mix screws 2.25 turns out.
main jets = 160.
air correctors = 155.
emulsion tubes =F-36 ( stock) with the top 2 holes sealed by epoxy compound ( apparently sealing the 2 holes at top helps with flat spot @ 4.500rpm) the guys on the org have reported good results by doing these mods so i am going do them soon just got to find a weber parts suppiler in the UK.

Dave.

**Yorky** · 05 Nov 07, 12:20 PM

Without jumping to conclusions and wasting time and money on the Weber Carbs have you checked the Marelli Digiplex CDI Unit ? The symtoms you describe are very similar to when this unit is malfunctioning. Check the connections in the block connector are sound. Swap yours with a good 'un to see if this cures the problem. Mine experienced these problems and it was the CDI unit. A temporary fix by taking the back off and getting the joints re-soldered helped for a while but in the end i had to source a replacement part. As a foot note the Weber Carb has been spot on with no trouble whatsoever.

**Dave-M** · 06 Nov 07, 08:55 AM

I have cleaned out the weber and reset everything and balanced the barrels ( throttles) and now it's running on 2 cylinders again and it's running nice and even @ the moment, i will certainly have a look @ the cdi's and check them out knowing my luck it will be something exspensive

fingers crossed etc it's ok now..

Dave..