40's versus 32's

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tony
Cucciolo - the Lil Pup
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Joined: Fri Oct 03, 2008 10:45 am
Location: hong kong

40's versus 32's

Post by tony »

My '76 900ss has the PHM 40 carbs fitted with Conti's. I also have the orig PHF 32's .

Why isnt there a choke for the PHM 40's?

Do the smaller PHF 32 Dell"Orto's idle better than the 40 PHM's

Is there much loss of power compared to the PHM 40's. Do most owners use the larger or small carbs

Bike goes well with the bigger carbs, and starts no problems. Just a pain for the neighbours whilst I warm up the bike without a choke, and riding thru traffic isnt alot of fun.


tony
1974 GT
1976 900ss

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Craig in France
Cagiva Gran Canyon
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Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Post by Craig in France »

Hi Tony,

As with most things in life :) , it's a trade ...

40s will give you more power at the top end, 32s will give you more tractability lower down. 36s are sometimes quoted as a fair compromise.

I don't know the historical reason why the PHM series had ticklers and the PHFs enrichers ('chokes'). However, the body castings are different.

Presumably the annoyance you're causing your neighbours is because the engine won't idle until it's warm? There is another solution: simply start the engine and ride off (gently, of course, at first ....)

Even with carbs with enrichers, these are really only intended to be used to start the engine - they should be snapped completely off once it's fired. That's what Ducati instructed in the "How to Use the Motorcycle" section of the owner's handbook :-)

"Once the engine is started, bring the air control lever to the running position ...:

And indeed, if it's properly set up, the bike will idle by the time you need to put your feet down.

HTH

Craig

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tony
Cucciolo - the Lil Pup
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Joined: Fri Oct 03, 2008 10:45 am
Location: hong kong

Post by tony »

Thanks Craig

Good to know that the 32's are better low down. I may look at changing over to see how it goes, as can do without the top end

My bike doesn't idle smoothly until the engine is warmed up and even then sometimes doesn't remain at a constant idle speed even when it is warmed up.

Starts easily but by the time I run around the the LHS and get the bike off the stand, it has often stalled, so have to start it again

Anyway thanks for your reply - was helpful
1974 GT
1976 900ss

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Craig in France
Cagiva Gran Canyon
Posts: 882
Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Post by Craig in France »

tony wrote:My bike doesn't idle smoothly until the engine is warmed up and even then sometimes doesn't remain at a constant idle speed even when it is warmed up.
Sounds like the carbs need cleaning anyway :-) ...

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