1969 750 Dellorto VHB 30 jets

S

Simon Yates

Senior member
I am going to buy some Dellorto spares.  Before I do I need to finalise the list of parts that I need.  As it arrived, my 1969 750 S was fitted with VHB 30 CS / CD carbs with the list of jets below.  Do note that the carbs have the accelerator pumps. 
It does need new Choke valves, new Interface plate O-rings and 40 ? elbows (#9330) so that I can mount the carbs horizontally.  The accelerator pump ball bearings (#7185) and one atomiser were missing.
Needles  V9 - Green bible says V3/2A
Main Jets 42 ? Green B says 125
Idle Jets 50 ? GB says 55
Choke Jets 80 - ??
Atomisers 265 (1 only fitted!!)
I suspect that some may be astonished that it actually ran, so I would really appreciate your advice.  A useful starting point would be the list of jets fitted to a 750 that does have accelerator pumps.
 
Simon,

Stock fitment VHBs for Laverdas did not have accelerator pumps.  Your carbs were probably originally fitted to a Guzzi.

I tried long and hard to get a set of those working properly on my GTL, in the end I threw them in a box and bought a NOS pair of the correct type that popped up at the right time.  If the pumpers refuse to work properly, you can de-activate the pumps by removing the spring and plunger.

Needles are either V3(preferably) or V6, the V3 has not been available for quite some time.  Needle jet AN265, main is in the 125-130 area, idle 50-60, choke 70.

I can supply choke plungers, jets and gasket sets, correct NOS inlet stubs along with insulation plates and o-rings.  Need to check if V3 needles(accurate reproductions) and the corresponding jets are in stock.

piet

 
I received a nice set of VHB 30 AD/AS from Dellortopaddy today.  I should stand a much better chance than trying to get the ex-Guzzi VHB 30 C's to work properly. 
The 50 degree inlet elbow's mean an awkward job of shortening / grinding off the cable outer.  I am waiting for four o-rings before I can fit them and hopefully have a ride this weekend! :D
 
don't try to shorten only the outer cable Simon, you are bound to damage the inner,

if you must re-use your existing cables, then unsolder the nipples at the end (can be either end) and slip the outer off, then remove the ferule, shorten the outer and re-solder the removed nipple,

or buy a kit of parts and make up brand new ones,

The Old Duffer in Greenwich (82 year old John Philip, you met him at baskers with his 1200 anni) has all the parts you need by the shed load, enough to re-cable about 50 Laverda twins! I am sure he would willingly help,I can put you in touch if you would like.
CLEM
 
I can't over stress this with Open Mouth VBH 30A's - You can not restrict the intake with a filter or Cones. They will not work no matter the size of the main jet or Exhaust used. They are Hi-Velocity Free breathers.

25 Main Jets for the OEM Duel DMC Pipes with cones and up to 32 Main Jets jets for 2 into 1 pipes open mouth.

The open mouth VHB 30A is a great Carb for a 750 Twin as long as you keep it clean and change the oil at least once a year and stay off gravel roads.

Forget Air Filters - PERIOD.
 
I have ordered a Venhill throttle cable kit and will get an experienced guy at work to solder the throttle nipples in place, so hopefully they will last.
Message understood regarding the the air filters.
I was tooooo optimistic about riding this weekend.  The cable issues and my poor close-up eyesight are not helping regarding setting the timing.  The new piston stop works well with a spot-on 80 degree difference CW and CCW.  The result is that the  original saw-cut showing TDC was about 3-4 mm out of place. 

 
and I am still figuring........

how did you mount the degree disc Simon, I have not found my adapter nut, still looking

CLEM
 
I cut a 44.0 mm hole in the degree disc to fit over the existing crank spigot.  It is then held in place with a couple of strong magnets while the timing operation takes place.  It is then so easy to realign to TDC and check the timing - well it would be if I could see what was happening and my glasses would stay on.
 
nothing like checking Shaun
so that you DO ACTUALLY KNOW
instead of assuming or hoping
I always find it very satisfying and enjoy doing it.

not a lot wrong with relying on what should be OK, as most do, but if there is a lot more enjoyment to be had, then I, personally, always grab it, and it is usually free!

I like your strong magnet idea Simon, I never thought of that one.
CLEM
 
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