Tuning - carbs hints

[MarcoPau]

Hello, I bought a Valentini with a tuned engine: it's a 390 cc (66 mm pistons) with PHBH 30 BS carburettors, 34/26 mm (IIRC) valves, 2 in 1 exhaust. The bike rides great at high revs, the problems are at slow speeds and starting: I often do some sort of double declutch blipping the throttle before starting on first gear, and when I gradually open the throttle the bike won't push. No problems if I run at full throttle.

The sparks are dark brown with black residues, even thou I lowered the maximum jets from 132/135 to 130/132. Air inlet is a cone filter on the front carb (looking back), and open on the rear carb, with a "shield" coming down the tank.

Settings: 266T with SX 15 needle (first notch on top), max jets 130 front, 132 rear, min jets 50, start jets 65, float 11,3 g.

Recently I've been given a few hints around, but wanted to ask you for advice. I've been told to fit two nozzles (now the holes are closed with two little bolts) for the balance tube and to use them also for balancing with the vacuum gauges (I set the gas valves' sheaths manually). Then one told me the 266T with SX 15 needle are absolutely no good (sounded a bit weird cause 500 sport used 266T...) and recommended me to get a 264T or BC with X24 (or X18) needle. Plus, one told me to get 90 degrees pipes to fit two cone filters towards up (this thing was said also by Lambertini at a meeting). I will use the strobe light today so that at least I can check if the timing is correct.

Well, for now thanks a lot for your attention!

Lamps

[elektrobank]

Hello, I bought a Valentini with a tuned engine: it's a 390 cc (66 mm pistons) with PHBH 30 BS carburettors, 34/26 mm (IIRC) valves, 2 in 1 exhaust. The bike rides great at high revs, the problems are at slow speeds and starting: I often do some sort of double declutch blipping the throttle before starting on first gear, and when I gradually open the throttle the bike won't push. No problems if I run at full throttle.

The sparks are dark brown with black residues, even thou I lowered the maximum jets from 132/135 to 130/132. Air inlet is a cone filter on the front carb (looking back), and open on the rear carb, with a "shield" coming down the tank.

Settings: 266T with SX 15 needle (first notch on top), max jets 130 front, 132 rear, min jets 50, start jets 65, float 11,3 g.

Recently I've been given a few hints around, but wanted to ask you for advice. I've been told to fit two nozzles (now the holes are closed with two little bolts) for the balance tube and to use them also for balancing with the vacuum gauges (I set the gas valves' sheaths manually). Then one told me the 266T with SX 15 needle are absolutely no good (sounded a bit weird cause 500 sport used 266T...) and recommended me to get a 264T or BC with X24 (or X18) needle. Plus, one told me to get 90 degrees pipes to fit two cone filters towards up (this thing was said also by Lambertini at a meeting). I will use the strobe light today so that at least I can check if the timing is correct.

Well, for now thanks a lot for your attention!

Lamps

i'm running phbh30 on my 501camel, and i'm playng with carburettors

from my little experience i can tell you to try and reduce a little the min jets from 50 to 45 and see how the spark plugs look then try to vary the leghts of tubes from cone filter to carb, put a filter also on rear cilynder too...

you have a rich mixture, try to lean a little bit
remember to chek both spark plugs every time you do a variation in carb settings, remember to control every time the throttle cable play on each carb and equalize them, everytime you do a mods to carbs, go for a ride,push it hard then shut off and check plugs

vacuum balancer and other mods are no good now, fix the problem with your current/original valentini set up and you will be fine

this will take a lot of time but in the end you will be very happy!