Dellorto PHM40s

[Throwley]

I also checked the needle valve (K4), main jet (AB265) and idle jet (152) were the same on both carbs.

Dave, I just noticed your jetting for the carbs.
You have 152 for the idle jet - this is the main jet, the idle should be in the late 50s. If you have 152 in the idle I'd be very surprised! What you have as main jet is the needle jet, and needle valve is actually needle.
Obvs. jetting is very dependant on camshaft, exhaust and intake systems, but what I found worked best on my 998, with B10 cam, K&Ns, with both Lafranconi comps and Kehin shorties which are about halfway between standard and the Lafr. Comps. restrictionwise is...

• Needle: K19, third slot

• Needle jet AB268

• Main: 150

• Idle: 60 (which was a bit rich with the shorties)

• Slide: 50/3

With the standard pipes refitted at MOT time it runs best with just a drop on the idle jet to 57, and refitting the standard 60/5 slides.

[peakrock]

Thanks for the comments about the Dellortos - I have no experience of them on a Guzzi so it's good to hear from someone who has. I did a compression test - all good. Checked for sparks at both plugs and checked the timing which all seemed ok This engine has the Sachs electronic ignition and I suddenly noticed that the pickup sensor PCB was very close to the stator. This guzzi engine has also got an uprated alternator with larger alternator windings with a corresponding longer stator. When mounting the PCB which sits in front of the stator it was necessary to make longer studs for it.

When I took the PCB off I could see that the stator protruding lugs had been rubbing on the board, right where the optical sensors were soldered to the board. They're protected by silicone sealant which had been rubbed away such that the stator could contact the soldered joints with the faintest of pressure on the board. I think the board may warp slightly when the engine is hot so I spaced it out further. I also cleaned up the soldered joints and put araldite over them to provide decent protection.

Once it was retimed and put back together it started up after a couple of goes and ticks over nicely. Another road test tomorrow should confirm if that was the problem.

Another Dellorto question: these carbs have got polished trumpets with mesh over the intake and no air filter I'm minded to put K & N filters on them, is that what fellow carburettor owners do?

Cheers Dave

[peakrock]

Just a quick update to say it's running beautifully today so problem fixed. Thanks for the advice.