40mm carbs on a 85 Cal II motor

[Petrus Rocks]

Modding n '85 Cal II.  Possibly can get a pair of 40mm Dellortos.  Too big?  I ride the bike mostly in the country 50-80mph.  I have Franconi Competizione mufflers, no other mods.

[Gliderjohn]

I would say to big without cam and head work. You would probably use torque right in the street speeds range to boot. I sure much more knowlageable folk here can provide more detail.
GliderJohn

[pressureangle]

Carb size is largely dependent on port size. There is no benefit to carbs a lot bigger than the port, and plenty of downside. I'd say if your ports are 36mm or bigger you may assume they'll work pretty good. Even on my hot rod LeMans 1000 with raised ports and high compression, it still carburets better below 3500 at part throttle than wide open.

Is that an 1100cc motor? That will help, but ultimately the small ports limit the suckage at the carburetor.

[Karl Von]

I just swapped the stock heads on my cali2 motor with heads from a 96 Cali 1100 which had 36mm carbs from the factory.   The cali 2 heads had much smaller valves and intake ports.  So I would say 40mm on a stock cali 2 is too large. 

[pete roper]

36mm PHF's with matched manifolds and ports will deliver a much nicer and more easily tuned motor.

[Petrus Rocks]

Thank you for the response guys!
In general, I thought they would be too big, but I don't know the motor well enough.
 A pair of 36 mm's will be on order soon.  Now Karl, if I could get a pair of 1100 heads cheap that's a great idea.

[Rough Edge racing]

 Smaller ports have a higher velocity air flow and are more efficient  at less than full throttle...If the intake stubs and ports are matched the 36 MM carbs should make more power at higher speeds....For best response at lower speeds you may have to open the with a slower twist....
  Petrus and me discussed Mikuni flat slides because I have some experience with them and they have sharper throttle response compared to round slides that offset being a bit too large at lower speeds..

[guzzista]

 Not meaning to hijack the  thread, but just as  a general reference, my 94 Cali  1100 recently got 40mm PHMs . Of course the manifolds and intake tracts were matched to the  to carb id . They work quite well after a bit of jetting adjustments and work even better with a B10 cam which I later  installed. In my experience the butt dyno does not register any real increase, , but overall throttle response is improved and fuel mileage is still at 37/38 mpg as before with the 36's .  Later in the season the heads will visit the flow bench for additional massaging , however valve size will remain stock at 44 and 37 mm .