PHF 36 as/ad vs bs/bd

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Jakobsen
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PHF 36 as/ad vs bs/bd

Post by Jakobsen »

Hi all!
I`ve been looking at a pair of used reconditioned PHF 36 bs/bd for sale.
Could anyone tell me the difference between ad/as vs bd/bs?
They have been sitting on an Guzzi Lemans.

Thanks.
Håvard
-78 Darmah
-98 Supersport

Jakobsen
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Post by Jakobsen »

Ok.. think I figured out the difference myself after some research:

PHF 36 AS/AD: Clamp mounted
PHF 36 BS/BD: Rubber mounted

Am I right?
Håvard
-78 Darmah
-98 Supersport

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BevHevSteve
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carbie info

Post by BevHevSteve »

well, no, not always. The PHF36 carbies I sell [which are the ones available] are DD and DS models - which are rubber mount.

BMW used dells and the ones provided for their bikes by Dellorto carried the BD/BS...... Clamp mount.

DARMAH had CD/CS as Craig states below, which are clamp mount but have an additional little jet under the pilot jet.

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Craig in France
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Post by Craig in France »

Hi Håvard

I also used to think it was that simple, but, like Steve says, it doesn't seem so ...

For example, the later Darmahs had carbs called CD & CS. But the mounting wasn't any different from the earlier AD & AS models ..

Urh?

Craig in UK, sorry can't be more helpful :?

Jakobsen
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Post by Jakobsen »

Thanks for the input, guys.

Well.. why make it easy, right... :roll:

I looked at this page to get this information:

"The first letter after the numbers: B means rubber mounting, other letters were produced for specific applications and follow no rules (except PHM38/40 B's on BMW R90S)"

http://www.motorcyclecarbs.com/Dellorto ... bs_W10.cfm

Well I guess I`ll just by the carbs and check them out, it can`t be that different ( I hope). About 230$ for both reconditioned.

Thanks again
Håvard
-78 Darmah
-98 Supersport

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Craig in France
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AS/AD, BS/BD, CS/CD etc

Post by Craig in France »

Hi Håvard.

Yeh, I'll go along with that explanation!

(There's what I have before thought was an explanation in the Dello'Orto manual - go http://www.guzzitech.dk/05/05-10/05-10-01.htm. But it doesn't really work :) :? ...)

Thanks for the website link - haven't seen that one before.

Regards

Craig in UK

machten
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Post by machten »

The only definite difference I've been able to discerne between CS/CD and AS/AD is that they use a different mixture screw. The AS/AD screw is shorter and angled about 30 degrees from horizontal. The CS/CD screw has about 3-4 mm of elongated parallel extension before reducing to a finer point. I have been told that this is to give a more precise mixture. There may be some other internal plumbing differences, but I don't know. I'm told both carbs are fine for Darmahs, and that 77 models and some early 78's came with AS/AD. (But that's just what I've been told!!!!) My 78 had CS/CD.

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Craig in France
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CD/CS vs. AD/AS

Post by Craig in France »

Hi Machten

Ah, that would make sense; as I understand it, the change over to the CD/CS carbs on later Darmahs was to get them thru US emission standards.

(Interesting that your 78 uses CD/CS. My Euro-spec 79 SSD was still fitted with AD/AS.)

Ciao

Craig in UK

FabDuc
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AD/AS & BD/BS

Post by FabDuc »

Ciao,

Does anyone of you have experience with the jetting of the PHM40BD/BS type carburettors?
The AD/AS types require a 152 main jet, but in the manual of the MHR with the BD/BS carbs, the required main jet is a 135. Also the needle is different. Could a 152 be to big for this type PHM?
Thanks in advance,

Ernie
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Post by gorman »

Ernie,

Have you ever found an answer to your question about the differences between the AS/AD and BS/BD carbs?
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FabDuc
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BD-BS versus AD-AS

Post by FabDuc »

No,

never got it cleared!
The bike does run OK with the 152 main jet, (and bigger), but I have a problem in one of the carbs, first I have to solve that.....I do not have enough experience with this jetting yet.
Still, I'm waiting for the answer!
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Post by gorman »

I also have the PHM 40 BD/BS carbs in my bike and took the front one off yesterday. I've noticed it has a 145 size main jet fitted. I think the quoted jet sizes for the MHR is 135 and 140 iirc. That means the front and rear one takes different sizes?

I'll remove my rear one tonight to see what it's got - quite curious to see. I've inspected the carbs closely and wondered what the differences to the AS/AD models could be? Seeing that the A models had ticklers, I assume they didn't have the choke assembly, or did they?

Another thing I've been wondering is whether one needs to alter the jetting when running pod filters rather than the open bell mouths? Mine's got the pod filters mounted, so hopefully it'll explain the odd jet size..
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Craig in France
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Carb queries

Post by Craig in France »

gorman wrote:I also have the PHM 40 BD/BS carbs in my bike and took the front one off yesterday. I've noticed it has a 145 size main jet fitted. I think the quoted jet sizes for the MHR is 135 and 140 iirc. That means the front and rear one takes different sizes?
Yeh, can happen. Some people - then and now - recommend running a larger main in the rear pot to keep it cooler. See also my response below to your query about air filters.
gorman wrote:I'll remove my rear one tonight to see what it's got - quite curious to see. I've inspected the carbs closely and wondered what the differences to the AS/AD models could be? Seeing that the A models had ticklers, I assume they didn't have the choke assembly, or did they?
Not so simple. 32 and 36mm AS/AD carbs DO normally have choke assemblies.
gorman wrote:Another thing I've been wondering is whether one needs to alter the jetting when running pod filters rather than the open bell mouths? Mine's got the pod filters mounted, so hopefully it'll explain the odd jet size..
Rule of thumb is to increase the mains when running bellmouths or K&N-type filters (which is what I guess you mean by 'pod filters'?) in place of fully filtered air boxes.

HTH

Craig

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Post by gorman »

Thanks Craig. I've removed the rear carb since posting last time and it has a 155 main jet.

Here's what my jet settings are at current: front (rear): Needle K4 position 2 (K4 position 2), Main jet 145 (155), Pilot 70 (70), Choke jet 60 (70), Slide 60/1 (60/1), Needle jet 265 AB (265 AB). It seems these settings are close to the "standard" settings published, except for the main jets that's slightly different and the pilot jets that's 70 instead of 60.

I'm going to replace the front cylinder's 145 with at 152 and leave the 155 on the rear one. What difference would the 70 vs. 60 pilot jets made? I might want change these to 60 as well - the settings should then be very close to the listed numbers in Stephen Eke's book.
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Craig in France
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Pilot jet size

Post by Craig in France »

gorman wrote:What difference would the 70 vs. 60 pilot jets made? I might want change these to 60 as well - the settings should then be very close to the listed numbers in Stephen Eke's book.
The pilot jet - what Dell'Orto misleadingly call the "idle jet", btw - is in operation at around 1/8- 1/4 throttle opening - what Dell'Orto call the "Progression phase".

You probably won't notice a lot of difference between a 60 and a 70, except for burning more gas - so your plugs might show a tad sooty. I wouldn't be surprised if your DPO had the bike set up for track use, btw.

But the jets aren't expensive, so I would be tempted to try a set of 60s and see what happens.

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