300 carb advice

[turps]

Hi, I am going to replace the carb on my 300 Pro. Dell Orto PHBH26BS, I've been checking prices online and the cheapest genuine one is from a scooter shop. Just looking for confirmation that they are all the same dimensions, cheers

[pschrauber]

Nope they can be very different there are the standard ones in bare alumiuim, the racing versions are in black or in red these have often different idle jets instaed using nozzles.

To the PHBH inbetween there where even standard ones in bare aluminium made with idle nozzles instaed of jets, then there can be many different types of needle nozzels mountet, from  type AS to type T there are 12 different versions!
(AS, AV, BC, BN, CF, CU, DG, DN , EF, M, P, and type T).

Ask the seller about the mounted jets and nozzles (Standard are 5mm idle jets and 6mm main jets and AV needle nozzles).

Also the float set up can be different too, but with not big effect to the air - fuel mixture.

[turps]

2 hours ago, pschrauber said:

Nope they can be very different there are the standard ones in bare alumiuim, the racing versions are in black or in red these have often different idle jets instaed using nozzles.

To the PHBH inbetween there where even standard ones in bare aluminium made with idle nozzles instaed of jets, then there can be many different types of needle nozzels mountet, from  type AS to type T there are 12 different versions!
(AS, AV, BC, BN, CF, CU, DG, DN , EF, M, P, and type T).

Ask the seller about the mounted jets and nozzles (Standard are 5mm idle jets and 6mm main jets and AV needle nozzles).

Also the float set up can be different too, but with not big effect to the air - fuel mixture.

Thanks 

[peterb]

Are you sure it is a PHBH26 that you want? Pretty sure that a 300 Pro would have used a PHBL26 carb. The main difference is in the pilot passage ways, the PHBL works on the fuel passage way, with the adjusting screw closer to the reed block side, the PHBH works on the air with the adjusting screw located toward the back of the carb.

[carl ekblom]

PHBL 20-26mm

PHBH 26-30mm

Think the PHBH came before the PHBL but don´t know when they appeared🤔

[fourex]

Original carb on Fantic 300 Twin Shock is Dellorto PHBH 26 BS.

Refer attached, mine still runs very well on these original settings in Australia on 95 or 98 RON unleaded petrol.

I've bought parts from these people with good success, www.dellorto.co.uk

PS: Not an air screw on the PHBH 26 BS, but a fuel screw..

 

Edited July 9, 2022 by fourex
Fuel Screw, not Air Screw.

[sherpa325]

I am pretty sure the PHBL was first used in the early 90's when the GasGas went to the case reed motor and they were looking for a smaller [as in physical size] carbie to fit in the reduced space. I think they were used on mopeds as a 22/24mm and were bored out to 26mm for the trials bikes.I have a PHBL and a PHBH and they both have the mixture/air screw in the same position - on the engine side.

 

[fourex]

Yes, I believe it's the suffix, such as AS/BD/BS/CD/FD/RD that denotes whether it's got an air screw or fuel screw. Don't know which is what, other than BS being fuel screw.

As far as "turps" is concerned, I'd stick with the original PHBH 26 BS, because we at least know what the original jetting specs were, and one can make minor changes from there if one doesn't like those settings.

[carl ekblom]

Lets see🤔......BS (sinistra?) is a left hand carb, BD (destra?) is a right hand carb.

Generally, if idle mixture screw is at carb outlet, it´s a fuel screw. Is it at carb inlet, it´s an air screw

AS is a left hand carb with screw connector

These guys have a lot of carbs and parts  https://www.dellorto.co.uk/

Here also https://www.splatshop.co.uk/