VHB 29 setting for scrambler 350/73

[Roland]

what should this value be in normal condition, please?

Regards, Roland

[themoudie]

Aye Roland,

Ich glaube, die folgenden Einstellungen gelten für den Dellorto VHB 29 AD Vergaser, der im 350 Scrambler von 1970–1974 verbaut war:

Nadel = V13
Hauptdüse = 110
Nebendüse = 40
Schieber = 40
Nadelposition = 2
Nadeldüse = 265M

Der Abstand zwischen der Unterkante der Vergaserbohrung und der Unterkante des Gasschiebers hängt von der Öffnung des Gasschiebers und der Einstellung des Leerlaufreglers (im Uhrzeigersinn) ab, wie in Ihrem Bild gezeigt. Es gibt keinen festgelegten Abstand, er hängt von den individuellen Einstellungen der Maschine/des Vergasers ab.

Es ist leider nicht möglich, eine genaue Angabe zu machen.

Viele Grüße, BillR

Google translation:-

"I believe the following are the base settings for the Dellorto VHB 29 AD carburettor fitted to the 1970 - 1974 350 scrambler:

Needle = V13
Main jet = 110
Pilot jet = 40
Slide = 40
Needle position = 2
Needle jet = 265M

Depending upon the throttle slide cutaway and how far you have the throttle idle speed adjustment screwed in (clockwise), will depend the distance between the lower edge of the carburettor bore and the lower edge of the throttle slide, as shown in your posted image. There is NO defined distance, it depends upon the individual machine/carburettor settings.

Sorry, not to be specific, but it is not possible.

Good health, BillR"

[Roland]

Hi BillR,

Thanks!
I should be more specific in asking...

Cannot make the machine run in idle and at all.
Maximal gap is about 1.5mm, then the screw is blocked by the spring.

Yes, it is individual setting. But first i need the machine running to tune the idle.
Should i set it basically to values like these to attempt starting:
Zero, 0.2mm, 0.5mm, 1mm, 1.5mm(max)

[themoudie]

Aye Roland,

Whilst I do not consider myself "expert", when it comes to tuning carburettors, if you cannot obtain an idle, at all, it would suggest that you have a blocked pilot jet, rather than an incorrect setting of the slide height. I am open to comment from others, with more knowledge of the Dellorto VHB 29 AD carburettor. Personally, I have substituted the Dellorto instrument for AMAL carburettors on my 1974 450 MKIII.

I would suggest that you need to dismantle and clean the carburettor, its galleries and drillings, along with the jets. Then check your float height, reset the pilot jet adjustment screw (1¼ turns out (anti-clockwise) from seated and the throttle slide screw (2 turns in from starting to touch the throttle slide) to their base settings and then try starting the engine again.

Here is a link to an earlier post on this forum from somebody experiencing similar problems to yours.
Link: Motoscrubs_forum_posting_on_same_subject_earlier

The 'Stein Dinse" website should be able to provide you with further information and spares if you should require them.
Link: Stein_Dinse_website

If Stein Dinse are unable to assist you, then the UK 'Eurocarb' company website may have what you require.
Link: Eurocarb_website

Hopefully, this will help resolve your problem.

Good health, BillR

[Roland]

Thanks for your detailed answers!

2 turns in will result in 0.8- 1mm gap, just in the middle.

I will try again on monday, no job for sunday

I can assure, everything is nice and clean.

I am thinking of an ignition issue:
transducer is properly earthed to frame, but frame is powder coated and motor just bolted in.
Measured zero Ohm.
Should i add an additional connection cable from frame to motor?

[themoudie]

Aye Roland,

I am thinking of an ignition issue:
transducer is properly earthed to frame, but frame is powder coated and motor just bolted in.
Measured zero Ohm.
Should i add an additional connection cable from frame to motor?

Yes. Also, clean back the powder coating from a central earth to the frame for all your other electrical components. You can always use some nail polish, or car body underseal, to seal the central earth on the frame from corrosion.

Good health, BillR

[Jordan]

Should i add an additional connection cable from frame to motor?

That is always a good idea.
Redundancy improves reliability.

Carburettor settings from Ducati factory parts list, 1968-1973 models:

350 SCR, 1971-73
VHB29AD, with clip-on air filter
Float weight 14 grams
Pilot jet 45 (40 with 450 type air filter)
Valve cutaway 50 (40 with 450 type air filter)
Needle jet 265M
Jet needle V12 (V13 with 450 type air filter)
Needle clip position 2
Main jet 110
Starter jet 65

Note that these are not my recommendations, just what Ducati said.

[Roland]

Thanks!

What about gap of the sparkplug?
Is it 0.5 for points/coils and 0.8 for transducer?
Which plug for ducati transducer ignition?

[themoudie]

Aye Roland,

With the points ignition on my 450 MKIII, I used a 0.6 mm (0.024") plug gap. With the Ducati electronic ignition, I used 0.7 mm (0.028") and now that I have converted to an Electrex World ignition system, I use the same spark plug gap of 0.7 mm. Ducati, in their owners handbook for the 1974 450 MKIII, recommended that the maximum plug gap should NOT EXCEED 0.8 mm (0.032").

My regards, BillR

[Roland]

Very interesting and good to know.

Some tasks for tomorrow...