LAVERDAMANIA

Carbs:

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Throttle position 1/8 1/4 1/2 3/4 Wide open
Main jet
XX
XXXXXXX XXXXXXXXXX
Needle/needle jet
XX
XXXXXXX XXXXXXX XX
Throttle slide cutaway
XX
XXXXXXX XXXXXXX
Pilot jet and air screw XXXXXX XXXXXXX XXXXXXX XXXXXXX X

The red crosses mean where jets or throttle slide valve mainly affect the mixture: For instance, uncorrect mixture at wide open position means that main jet is concerned when
uncorrect mixture at 1/2 throttle position shows a wrong throttle slide cutaway, or a wrong pilot jet, or a wrong needle type.

- Dell'Orto needles sizes

A: Diameter of the cylindrical part in mm


B: Diameter of the tip in mm


C: Length in mm of the tapered part

 

  A B C
K1
2,45
1,75
37
K2
2,45
1,75
42
K3
2,50
1,50
39
K4
2,45
1,50
37
K5
2,45
1,50
39
K6
2,45
1,75
39
K7
2,45
1,25
37
K8
2,50
1,50
42
K9
2,45
1,50
39
K12
2,48
1,75
32

- Original carb setting for 1000 LAVERDA (Dell'Orto PHF 32, A11 camshafts):

Slide cutaway
60/2
Pilot jet
55
Choke jet
70
Main jet
120
Needle jet
265 AB
Needle
K1, position 2
Pump jet
35
Float height
18mm +/- 0,5mm

- Original carb setting for LAVERDA 650, 750 GT and American Eagle (Dell'Orto VHB 29):

Pilot jet
55
Choke jet
70
Main jet
116
Needle jet
256 N
Needle
2ème rang
Float height
18mm +/- 0,5mm (5,8 cl)

- Original setting for LAVERDA 750 S et SF until 1972 (Dell'Orto VHB 30):

Pilot jet
55
Choke jet
70
Main jet
125
Needle jet
265 N
Needle
V 3/2 A, 2ème rang
Float height
18mm +/- 0,5mm (5,8 cl)

- Original setting for LAVERDA 750 SF1, SF2, SF3 (Dell'Orto PHF 36):

Pilot jet
55
Choke jet
70
Main jet
140
Needle jet
265 AB
Needle
K2, 2ème rang
Float height
18mm +/- 0,5mm (5,8 cl)

 

- Carbs tuning bases:
(First of all, I'm sorry for the rather bad english I will use below. I have not been helped to make a good translation, it should be corrected soon...)
The correct tuning of the carburettors is very important as problems can occur to the engine (overheating, holed pistons) if it is not the case. Keep in mind that the best
results (performance) are achieved when the tuning is almost lean but, in that case, the engine temperature is too high. Then, the ideal tuning (for durability) is a slightly
enrichment with regards to the best performance obtainable.
First, it is necessary to set the carburettors with the original values: main and idle jets, needles, atomizers, throttle slide cutaways, float height, ect... It is also necessary that the
carbs are not worn or partially blocked. In most cases, it will be sufficient to change the worn parts and to clean the carbs (ultrasonic way is the best) but, in extreme cases,
it will be necessary to replace the carbs. In other words, it is VAIN AND DANGEROUS TO TRY TO TUNE A WORN OR BLOCKED CARB!
When the carbs are perfectly cleaned and tuned along original conditions, all seals and gaskets replaced, without any air leak (engine idling), you have to analyze the symptoms:

- Symptoms:
- Symptoms of lean mixture:

1- Concerns main jets, needle level, float height, air leak:
-The plug has a satin white colour, even light yellow. Watching with a magnifier, the electrode edges are slightly rounded, eroded.
- The engine starts but it stalls when you suddenly accelerate.
- The engine splits and misfires.

- Slightly improvement when the choke is on.
2- Concerns the idle jet, throttle slide cutaway, air screws, air leak:
- To start a hot engine, you have first to action the pumps or the choke.
- Bad idle, sometimes the idle speed remains too high during 3/4 seconds then shut down quickly.
- Splits or misfires, above all at low engine speed..
3- Concerns choke jets, choke cables or plungers state:
- Starting the engine is easy when hot but not when cold.
- Symptoms of rich mixture:
1- Concerns main jets, needle level:
- The plugs have a sooty black or dark brown colour
- Easy starting when the engine is cold but not when hot.
- Lack of power of the engine, it is weak, it vibes during acceleration, black smokes from the exhausts.
- When the throttle is wide open, engine at high rpm, it seems that it has almost more power if you slightly release the acceleration control.
- Slightly worsening if choke is on.

- Tune-up the carbs: Methods:
To do first: Carbs must be perfectly cleaned. Needles, jets, throttle slides must be new or in perfect state. Carbs must be synchronized (in a first time, with a tool under the
throttle slides). There must be some plays to the cables, gaskets and seals must be new or in perfect state. Choke plungers must be free and the springs must be in good state.
The ruber caps of the choke cables (on the carbs) and the seals of the choke system on the carbs must be in very good state to avoid air leak at these points. Pumps levers are
free and in good state. Pumps membrans are new or in good state. Basic tuning is original (see above). Floats height is correct. No air leak.
Two complementary methods can be applied: The dynamic tuning and the plug "reading".

- Dynamic tests:
Phase 1: Main jets: Start the engine, warm up some seconds then accelerate at WOT through the gears:
-If the engine has a good response when cold but less when hot, tuning is too rich.
- If the performance are better whe hot that when cold, tuning is too lean.
Phase 2: Main jets, needles: In 5th gear, keep the acceleration stabilized around 5500 rpm (at around 8/10 of the WOT) then suddenly decelerate until 1/2 of the WOT:
- If the engine hesitates or misfires, mixture is too rich.
- If the engine seems almost run better, mixture is too lean.
- If the engine slows down immediately, without misfires, it's correct or close to correct.
Phase 3: Idle jets, needle height: From idle, suddenly accelerate:
- If the engine seems weak, feels sluggish, vibes, mixture is too rich.
- If the engine hesitates, misfires, splits through the carbs, even cuts then accelerates, mixture is too lean.
Phase 4: Main jets, needles: Engine at constant speed on highway, action the choke and watch what occurs in the firts seconds:
- If the engine hesitates, misfires, decelerates or even cuts out, mixture is too rich.
- If the engine slightly decelerates without too much misfires, tuning is correct or close to correct.
- If the engine seems to run better, mixture is too lean.
Phase 5: Idle jets (or air leaks): Suddenly accelerate through the gears on a highway then suddenly decelerate:
- If the engine slows down too slowly, with a deep and "weak" sound, mixture is too rich.
- If the engine misfires, detonates, mixture is too lean.
- If the engine slows down quickly without detonations, mixture is good.
Phase 6: Idle jets: Engine at idle speed.
- If the engine idles some seconds then slows down and cuts out, mixture is too lean.
- If the engine, after having briefly and slightly accelerated, revs then has some difficulties to slows down, then slows down and cuts out, mixture is too lean too.
- If the engine idles but is weak when you biefly accelerate (too low acceleration), mixture is too rich.
- If the engine revs immediately, without hesitation, when you briefly and suddenly accelerate, it's ok.

As a good result, the engine must run well at any speed and any condition, without hesitation, misfires or detonations, with a great power, and must get a great and stable
idle. Once these conditions obtained, just make the modifications below for durability:
- On triples, fit larger main jets: + 5 points on lateral cylinders, + 10 points on central cylinder.
- On twins, increase the main jets: + 5 points.

- Plugs readind (main jet test):

Buy several brand new plugs (at least 20), good thermic range. Reading a plug must be done only with a new plug.
Fit a new plug before each test.
On private road od track, stabilize the speed to top speed during 10 seconds, then shut the engine before you shut off the throttle.
Remove the plugs and watch to the electrode colour and shape (a magnifier is required):
- Sooty black colour, soot is clearly visible with the magnifier, electrode shape is intact: Too rich.
- Black or dark brown colour, not or few soot, intact electrode shape: Slightly too rich.
- Satin white colour, even light yellow, eroded electrode shape (rounded off at the edges): Too lean, DANGER! Don't restart without fitting larger main jets!
- Light grey colour, intact electrode shape (or very small erosion visible with the magnifier): Slightly too lean, danger for the pistons!
- Light brown colour on the electrode, dark brown on the plug body, electrode sha

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