Dellorto Carb help please

[peakrock]

The Type 1 I'm rebuilding has a Le Mans engine bored out to 950cc and has a pair of Dellorto PHM40 AD carbs on it. I'm at the point of doing the throttle cables and choke - but there doesn't appear to be any choke function on the carbs...

I've looked on the web at pictures of the PHM40 and on those it shows a choke tube with either a cable operated plunger or a lever operated plunger as a modification. Al and I had a look at these carbs this afternoon (as I know very little about the carb engined Guzzis) and he's not seen these carbs before. We think they must either be very old carbs or maybe modified just for racing use? Can anyone help please with whether or not a choke function could be provided? I'm also getting advice that a pair or PHF36 ? carbs would be a better bet if I want some tractability etc?

Thanks Dave

[Throwley]

There's no choke on those, but starting mixture is enriched by tickling the carb, oldschool style. Off a Ducati 900, I think, my friend's MHR had a pair. How modified is your LM engine? What cam does it have? What valves? Has any porting work been done?

If you can tolerate the faff of tickling the carbs before starting, I think these would work very well indeed with the standard LM P3 cam on a big bore engine, but perhaps the B10 cam would make for more tractability as the p3 is all top end (which of course would suit the bigger carbs). 36s would probably improve tractability, LM s with standard mid-sized valves, standard P3 cam go very nicely on 36s.

Pretty sure you'd have change left over if you sold these to buy a pair of 36s!

[peakrock]

Thanks, that's really useful information. I don't know what cam the engine has but I've asked the previous owner who stripped it down and rebuilt it so fingers crossed. I guess it depends whether the engine was originally modified for more torque or outright power.

Perhaps the sensible option is to go ahead with the existing carbs and see what it's like when it's running, tbh I'm not one for fiddling around with jet sizes etc but maybe that's also been taken care of (he said hopefully!)