Scuse me in advance for my bad english regarding the technical words. So, any
suggestion is welcome...
All photos from Pat, who races his triple in the European
P2 unlimited class championship.
first part concerns the LAVERDA 1000 and 1200 tuning.
A special page
for the 750 twins will follow.
Thanks to Patrick and Doug for their help.
AND 1200 ENGINE TUNING
120 or 180°?: Same
work will allow almost the same results on both 1000 and 1200cc engines. However
the 120° engines are easier to tune-up thanks to their better smoothness,
even if the 180° will give all its bad character and its special roaring which
allow so stronger sensations...
or 1200?: It is evident that a 1200cc engine can allow
a great power with an easier way than the 1000. But some pilots racing their bikes
in classic championships prefer the 1000cc because they think that this engine
revs better and is more homogeneous. So,
the opinions are divided, they depend often of the tracks used.
power can be expected?
100 hp to the rear wheel (115/120 engine power) is a good average, regarding torque,
reliability and reasonnable budget.
Consequently, to get a power really
better than 100 hp to the wheel is an extremely hard and rigorous job, asking
for hi-technology systems (ceramic coating for instance) or for very expensive
and radical mods (monoblock cranks, ...)
So, we will aim in this page
a basis of 100hp to the wheel, which can be possibly improved thanks to more radical
Engine head: -
Valves: 35 to 35,5 mm for the exhaust valves, 39,5 to 41mm for the
inlet valves are required. To get 1000 SFC (35/40,5) or Jota (35/39,5) valves
can reduce the cost. Valve set width must be narrow, about 0.5mm inlet and
1mm exhaust, which says that reshimming operations will occur frequently.
Special bronze valve guides are better, they must be slimmed down in the ports.
Ports profiles must be modified and polished. Valve springs can broke, especially
with the 7C cams at very high revs, involving damages to the cams and buckets.
With the 7C, it is necessary to drill the head where thesprings are located
in order to not crush them. Some engineers put twin springs, it is then necessary
to modify the valves cups and the guides. This mod is effective.
Camshafts: The available camshafts for the Laverda
triples can be improved, a lot of work is still to do on them (they have been
conceived 30 years ago!). Doug Home in Australia is working for new cam designs,
his work should allow good results soon.
Waiting for that, the cams available
are the factory 4C and 7C cams, or the Axtell coming from the US.
engineers are triying to find more answers, like mixing 4C/7C, modifying the cam
lobs or the timing with adjustable sprockets or at least different valve gaps.
For the 4C, which allow a better power at high rev without loosing the mid range
torque, it seems that the good timing is obtained with closer gaps than preconized:
0.15 IN and 0.20 EX. For the 7C, used on the fastest and straight tracks (good
power at high revs but they kill the mid range) the gaps can be set at about 0.20
IN and 0.25 EX. As mentioned above, the 7C can broke the valve springs at very
high revs and sometimes the pistons.
The Axtell cams are a good improvement
for power and torque face to the factory cams, but the power drops off quickly
over 7800 rpm. The Doug' work actually done in Australia should allow great results
on all the power range, we are all waiting... At least, the cams sprockets
can be lightened by drilling them.
- Cam buckets:
The small holes allowing to drain off the air when the buckets are lifted down
by the cams must be slightly enlarged on the top of the bucket, in order that
the oil film cannot be broken at high revs. A good improvement can be found by
drilling 1mm from the top edge of the buckets liners, allowing oil to stay at
Twin spark system: Some engineers propose to modify the cylinder
head to fit 2 spark plugs per cylinder, matching with a twin spark ignition
system. This allows a better combustion but also it is then possible to retarding
the ignition advance and avoid the overheating. A special ignition is required
Cylinder block, pistons:
- Concerning the cubic capacity, there is a choice
to do beetween the original 1000 Jota parts (75mm pistons), the 1200 Mirage ones
(80mm pistons), and other bigger pistons which can help to increase the cc. However,
the biggest recommended size is 81mm in order to keep the required liner
thickness. If the 81mm size is chosen, it is necessary to adapt new liners (the
Citroën BX liners can be adapted to the Laverda block) and to fit new
forged 81 mm HC pistons (Accralite and J/E), with possibly mods to match with
the big valves. The Accralite ref. 1124804 don't need this mod though. In
case of such a modified cubic capacity, it is naturarly necessary to adapt the
- The original preconized liner/pistons
clearance is too tight for a racing purpose, a clearance of 0.11mm is required
(original average is 0.08mm)
- One of the main
problem in racing condition is the pistons overheating. To
limit the piston temperature, it is possible to slightly retard (which matches
also with free-flox exhausts) the ignition advance if the system is good (bad
results with original Bosch ignition), or fit a twin spark ignition system.
But one of the best way to control the pistons temp is to fit at the rear of the
cylinder block 3 oil jets, jetting oil on pistons sides. The position of
these jets must be precise in order to avoid blow-by phenomenal. The oil pressure
must be sufficient (see below).
- Compression ratio: To
adjust it, some engineers rectify the cylinder block base (-1mm) or even remove
the cylinder block base gasket instead of working on the cylinder head.
We are speaking here about a tuning on an original Laverda
engine basis, so we keep the assembled crankshaft basis.
cranks are very solid, tuning them is often limited to a careful balancing, to
the alternator and starter freewheel removing and then to cut the conical end
of the RHS of the crank to improve the ground clearance. However, it is possible
to lighten and polish the crank for a better vivacity and security.
The Carillo rods are not a necessity except if the original rods are out of service.
In this case, it will be necessary to fit new needle bearings.
crankcases: They are often stiffened by welding near the engine
fixing points and around the central crank bearings. The oil case is often
partitionned off to avoid the oil charge loss.
is a very old debate beetwen those who use mineral monograde oil and those who
use only 100% synthetic oils... Some pilots are very happy with the Castrol R40
as it works weel in the old engines and because synthetic oils avoid a good engine
running-in and can made the clutch slipping. Some others arguing that the
synthetic oils are really a way to reduce the engine temperature and wear...
Each pilot has his own choice and some of them use other various solutions like,
for instance, a dual lube system, Castrol R40 in the engine and multigrade in
the clutch (a plate is then used to isolate the clutch from the engine oil), or
synthetic oil in the engine and mineral multigrade in the clutch!... The
oil pump output must be improved, 2 ways for that: Fit a larger big capacity pump
or modify the pump sprockets ratio. If the engine is a 1200cc, fit a bigger
oil cooler. At least, dry lube system are more and more used.
ignition: The original Bosch ignition systems were already junk
on road bikes, so in racing conditions... It is then necessary to get a serious
and reliable system. John Wilson (see the "improving" page of this
site, IIS ignitions) has done a special racing ignition system, light and compact,
including different programmable advance curves. The pilot can even order
its own curves when he order the system. The ignition can be removed easily and
quickly in case of problem (crash or mechanical problem). At least,
this ignition can be delivered with a twin spark output in order to match with
a twin spark cylinder head, which allow to improve the power and to retard
the initial advance of about 8°. The spark plugs must be cold, NGK 9/10
EV or EGV or Bosch W3DPO (platinium projected electrode, same plugs as the Porsche
carbs: A lot
of solutions are used, from the very big 38 or 40 Dell'Orto to the 38 and even
41mm (!) in Japanese carbs (Keihin). However, the best results in race seem to
be obtained with the 36mm Dell'Orto carbs. Some pilots are even saying that
the best results on various tracks are obtained with the 32mm Dell'Orto re-bored
to 34mm, above all for the 1000cc engine.
Main jets around 175/180, pilot
jets 65, 60/2 slides. Open bellmouths with 3 lenghts depending of the track, but
some riders prefer big capacity home made air box, without filter, which calm
the air input.
After a long use of 3 into 1 systems, it seems today that everyone
wants to use 3-1-2 exhausts which allow a better power at top end. Tube diameters
are generarly 40mm, the collector is a large capacity system. The conical end
shapes of the "silencers" have to be carefully conceived to keep
the homogeneity of the whole system. Some new systems, including a sort of
Exup, are experimented.
If allowed, an AvGas (aviation fuel) or a 105 leaded fuel is required.
Gearbox, secondary transmission: No big
changes to do. The main improvements to do are to chrome the selection drum and
to reverse the gears selection (1rst gear up and others down), the gearbox
is easier in racing conditions. As for the transmission, fitting a narrower chain
and sprockets(Zane style) is a good improvement.
transmission: Remove the Triplex and replace it by 2 single chains,
more solid and lighter, and remove the central teeth lines by turning them. The
clutch drum can be lightened too.
AND SUSPENSION TUNING
is a special page done by Doug Home (Australia): -Click
AND TYRES TUNING
is a special page done by Doug Home (Australia): -Click