950 Le-Mans 2 carbs

[Nigel]

I'm in the middle of a full engine rebuild on my standard 850 le mans 2.
Nowhere near starting it up yet, I'm a few months away from that.
The only main changes other than standard rebuild stuff is a P3 camshaft, 950 Gil conversion, light flywheel. - Heads and valves will remain standard.

My Question is : - will I need bigger than standard carbs, or do you think I can get away with using the existing ones ? If so what is recommended.
Any comments will be greatly appreciated.

[pete roper]

The 36's will be fine but since they are almost certainly worn out  you could, if you wish, try a set of 40's but in all honesty mid valve heads and 36's are a sweet combination. Let's face it, it's not going to be any sort of record breaking power monster so why not just make it nice to ride?

Pete

[Arizona Wayne]

The CX100 949cc/ LM II copy sold in US have 32 mm carbs, but some here put bigger carbs on these  smaller valve cylinder heads with no regrets, so you should be fine.

[5154guzzi]

FYI ,  the US only CX100 had the SP engine with the square slide  30`s as standard equipment.

[harrytief]

To mount the 36mm carbs you need to open the intakes to match the carbs...best done while you have the heads already off.
Harry

[Arizona Wayne]

FYI ,  the US only CX100 had the SP engine with the square slide  30`s as standard equipment.

FYI, my `81 CX100 has 30mm PHF round slide carbs. But you're right, I thought they were 32mm. 

[5154guzzi]

The PHF`s are the ones to have in 30mm.   Nigel,  You will have a much better running engine overall if you stay with the 36`s as Pete said. Going to 40`s with standard heads  `might` give you a little more zip above 5K rpm, but will diminish the engine`s flexibility where it really matters on the street.

[jacksonracingcomau]

The PHF`s are the ones to have in 30mm.   Nigel,  You will have a much better running engine overall if you stay with the 36`s as Pete said. Going to 40`s with standard heads  `might` give you a little more zip above 5K rpm, but will diminish the engine`s flexibility where it really matters on the street.

The dyno, 35 years exp with them & recent fuel consumption tests tell the opposite story (on my engines)
No dog in fight but 40's win everywhere, especially sub 5K, top end almost irrelevant to me, torque spread is the advantage (again to me)

Anyone with pair of PHM 40's they don't like have instant swap with pair of excellent 36's with range of jets, pm me

[Nigel]

Thanks guys for your opinions and advice.
I think I'll stick with the 36's and try it like that to begin with.
I'm happy with this as I'm rapidly running out of money..........
Nigel

[Dukedesmo]

My LM2 is now a 950, it has B10 cam & 40mm exhaust into Lafranconi 'competizione' pipes.

It has the standard PHF36 carbs, the only changes to setup being 148 main jets (which were actually fitted when I bought it as an 850) and whilst I've not dyno'd it to check AFR etc., it does run very well - although maybe a tad on the rich side?

I wouldn't think bigger carbs would do much.