Hi All- this is probably silly Q which I am not asking out of desperation as bike riding reasonably well...just wondering....may be a bad idea for reasons I don't know...
...but does anyone know if these carbs at links below could replace carburettors VHBZ 25 HS? If yes what mm size would I need?
They cost £37. each- not sure if there's a left and right version.. says "For Dellorto Carburetor PHBL 20/ 22 /24 /25/ 26/ 28mm Motorcycle Carburetors" They also say for 2-stroke so probably wrong...
AliExpress.com <https://www.aliexpress.com/w/wholesale- ... l.search.0>
Eurocarb sell various Dellorto PHBL carbs- look a bit like VHBZ 25 HS - "R2710 Dellorto PHBL 24AS 4 stroke"
https://www.dellorto.co.uk/shop/dellort ... -4-stroke/
Thanks
Matt
Replacement carburettors
Replacement carburettors
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Re: Replacement carburettors
I have Mikuni VM28 carburetors on my 1976 3 1/2 Sport. It took a long time to dial them in, but once I got it right I would never go back to Dellorto's. The biggest issue is mounting them...
I guess I'm trying to say that fitting different carburetors is never going to be straightforward.
I guess I'm trying to say that fitting different carburetors is never going to be straightforward.
Re: Replacement carburettors
i fitted a set of vm 34 mikuni's to my guzzi 650, getting the jets dialed in was a bit of a
struggle , but the result was worth the efford
aliexpress helped with stupidly cheap jet kits
i'm tempted to try a set of these on my 350 morini
https://nl.aliexpress.com/item/32962985265.html
would be nice if they could line up with the orignal airbox
struggle , but the result was worth the efford
aliexpress helped with stupidly cheap jet kits
i'm tempted to try a set of these on my 350 morini
https://nl.aliexpress.com/item/32962985265.html
would be nice if they could line up with the orignal airbox
Re: Replacement carburettors
Thanks for your replies huub and 70sbikes. Great that Mikuni 34 works- copies cost about £40-50 a pair so not bad price but are they OK to use or must be original as they are a lot more... I am interested in what else is possible- this ZSDTRP Maikuni PWK 28 30mm Motorfiets Carburateurs look good but if float bowl needs to horizontal as in pic I can't see how they could fit onto the engine...Can I ask what are the critical measurements I need to know to buy carbs? For instance what does the 34 stand for with the Mikuni? How did you know it would work/fit?
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Re: Replacement carburettors
the 34 is the venturi diameter , 34 would be too big for a morini , but they are available in other , smaller diameters.
the stock guzzi has a 30 mm phf dellorto , but it is too small for the 650 engine.
the bigger dellorto's were expensive , so gave the mikuni's a try.
i was thinking of using the ZSDTRP carb in a downdraft setting , straight on the engine , without the rubber elbow.
it is originally for a 250 single 4 stroke , so might work.
or might not, unless somebody tries we wont know for sure.
but when changing carbs the jetting is the challenge , if you never had to set up a carb it will be a steep learning curve.
the stock guzzi has a 30 mm phf dellorto , but it is too small for the 650 engine.
the bigger dellorto's were expensive , so gave the mikuni's a try.
i was thinking of using the ZSDTRP carb in a downdraft setting , straight on the engine , without the rubber elbow.
it is originally for a 250 single 4 stroke , so might work.
or might not, unless somebody tries we wont know for sure.
but when changing carbs the jetting is the challenge , if you never had to set up a carb it will be a steep learning curve.
Re: Replacement carburettors
I think the VM28 has a 32mm venturi, which is not ideal, but workable. I used NLM aluminium inserts (original part number 32.01.42) so the Mikuni would fit the standard rubber elbow, however, I did have to cut about 10mm off the length to uncover a jetting hole. I then chamfered the inner edge so there wasn't a sharp transition from the carburetor to the insert. It took me a while to work out the carburetors were jetted "2-stroke", so the air jet was missing completely! Also, I discovered the tapers on the jet needle made a huge difference in performance (more-so than the jetting). Thanks to a Ducati/Moto Guzzi trained mechanic, I was also able to get rid of the notorious Mikuni off-idle stumble. As huub said, it's a steep learning curve! But I love a challenge, and it was a lot of fun working out the different issues as they arose.
Regarding the Mikuni copies on AliExpress, I reckon they're so cheap it's worth a try! I'm a big fan of AliExpress, and most of the stuff I've bought has been top-notch.
Regarding the Mikuni copies on AliExpress, I reckon they're so cheap it's worth a try! I'm a big fan of AliExpress, and most of the stuff I've bought has been top-notch.
Re: Replacement carburettors
Thank you for this information- I see that it is not straightforward. It may be better for me to just try to get my Dellorto's to be in their best condition- I have replaced some parts already but slides, needles and atomisers not done.
Can I ask one more Q which follows 70sbikes comment on needle tapering making a big difference...Q: How much difference does needle wear and height/position affect running- would it produce a stutter/stalling at low revs ie. when pulling away at lights?
Thanks again in advance for any advice. Just trying to perfect here and still riding bike- did a 400 mile journey last week so things OK really.
Can I ask one more Q which follows 70sbikes comment on needle tapering making a big difference...Q: How much difference does needle wear and height/position affect running- would it produce a stutter/stalling at low revs ie. when pulling away at lights?
Thanks again in advance for any advice. Just trying to perfect here and still riding bike- did a 400 mile journey last week so things OK really.
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Re: Replacement carburettors
I’ve just bought a no PHBL 22 for an Italian lightweight to replace a worn slide Dellorto UB20F which to me makes more sense than a Mikuni as I can swap some jets and all parts are available for the PHBL from Eurocarb here in the UK. Easy to tune, a good carb and stub and flange fitting variants. Watch out for Chinese copies available elsewhere as jets can differ from genuine parts and you’ll be all over the place if you mix and match.
Regarding your poor running at low revs is something I’ve found with modern fuels as pilot jets may need upping or lowering depending on if it’s an air or fuel adjustment screw? If you can’t get a normal setting on the mixture screw (1 1/4 to 1 1/2 turns. I can’t remember the Morini setting) you may need to change the pilot jet?
I’d look at the needle after that.
Regarding your poor running at low revs is something I’ve found with modern fuels as pilot jets may need upping or lowering depending on if it’s an air or fuel adjustment screw? If you can’t get a normal setting on the mixture screw (1 1/4 to 1 1/2 turns. I can’t remember the Morini setting) you may need to change the pilot jet?
I’d look at the needle after that.