carbs
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MickeyMoto
- Posts: 2431
- Joined: 22 Nov 2008 17:41
- Location: Even further oop North
Re: carbs
'z'? 
I think the Zs have more drillings for vacuum gauge attachment and overflow for fuel flooding.
Or maybe the overflow drilling does not exist.
I think the Zs have more drillings for vacuum gauge attachment and overflow for fuel flooding.
Or maybe the overflow drilling does not exist.
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Fastmongrel
- Posts: 208
- Joined: 07 Nov 2022 22:37
- Location: Lancashire
Re: carbs
Official pedant checking in 
These are the Dell'Orto castings for the body VHB and VHBZ the venturi size is next then a variation letter AFAIK Moto morini only ever used B and H variants, the S stands for Sinistro or Left , D Destro or right side carbs not used on twins. The castings are common S or D only the drillings make them left or right handed.
date is first use by Moto Morini V twins (VHB and VHBZ carbs were used on other motorcycles)
1st series VHB 25 BS. 1973 Fixed float valve seat (these also have a more rounded float bowl with a different arrangement of fuel ways to the main jet.
2nd series VHBZ 25 BS 1976 screw in replaceable (and hence selectable) float valve seat
3rd series VHBZ 25 HS 1979 vacuum ports added. Later ones seem to have some small difference in the way the mixture screw drilling is done, but I am loathe to cut one open to find out if that's true
4th Series VHBZ 25 HS 1983? - brass vent tubes are fitted, to replace the open vents (overflow), later ones of these have plastic top caps.
cheers
Mark
These are the Dell'Orto castings for the body VHB and VHBZ the venturi size is next then a variation letter AFAIK Moto morini only ever used B and H variants, the S stands for Sinistro or Left , D Destro or right side carbs not used on twins. The castings are common S or D only the drillings make them left or right handed.
date is first use by Moto Morini V twins (VHB and VHBZ carbs were used on other motorcycles)
1st series VHB 25 BS. 1973 Fixed float valve seat (these also have a more rounded float bowl with a different arrangement of fuel ways to the main jet.
2nd series VHBZ 25 BS 1976 screw in replaceable (and hence selectable) float valve seat
3rd series VHBZ 25 HS 1979 vacuum ports added. Later ones seem to have some small difference in the way the mixture screw drilling is done, but I am loathe to cut one open to find out if that's true
4th Series VHBZ 25 HS 1983? - brass vent tubes are fitted, to replace the open vents (overflow), later ones of these have plastic top caps.
cheers
Mark
Re: carbs
Thank you for the replies. I have a 1977 3 1/2 strada and bought a pair of used vhb25bs carbs. When they arrived one is a vhb z 25bs are they interchangeable? as long as the jetting is the same.
The vhb 25bs has wear on the slide the other 'z' is in very good condition.
The vhb 25bs has wear on the slide the other 'z' is in very good condition.
Re: carbs
Hi,
In your case (77 strada) the VHB 25 BS and VHBZ 25 BS are interchangeable and the jets should be the same.
I would probably replace all jets with new anyway, with what you have in your present setup
for the record as standard 77 strada would have 112 main, 260K atomiser, E17 needle 50 choke.
The pilot jet standard was 50, but most people have reduced this to 45 or even 43.
You might find that the VHB has different floats to the VHBZ - the setting is the same.
Mark
In your case (77 strada) the VHB 25 BS and VHBZ 25 BS are interchangeable and the jets should be the same.
I would probably replace all jets with new anyway, with what you have in your present setup
for the record as standard 77 strada would have 112 main, 260K atomiser, E17 needle 50 choke.
The pilot jet standard was 50, but most people have reduced this to 45 or even 43.
You might find that the VHB has different floats to the VHBZ - the setting is the same.
Mark