TIPS
for 750 twins!
(With the courtesy of Martin Cutler, of the
Club Laverda NSW, Australia)
Insurance
Tip for 750 owners
Fit two small pieces of wire to the two centre studs that
act as an oil passage to the head-
This will ensure that the oil galleries
to the rockers will not be blocked by the studs. It can happen.
The resultant
damage to the cams and rockers is expensive to repair/replace. Lee Frame
Jetting for 32mm pumpers for 750
Mains up to 130
Pilots 55
Slides 50/3
leanest if you sit on the max all day you may need to go a little
richer or you'll be a little poorer. Steve White
750 Twins Basic Maintenance
The Laverda 750 Twins are, perhaps, the most simple, bullet proof motor that
the factory has produced. Preaching to the converted?
It seems that most
of the 750 owners in the Club do their own maintenance work with satisfactory,
if not, rewarding results.
This is not a slur on the excellent service available
commercially, but rather part of the nature of owning a twin cylinder machine.
The following are just a few tips that might not be explained so much in the excellent
owners manual. Photocopies should be available from the Club in the near future.
This manual contains exploded diagrams with factory part numbers. At least
the potential owner is treated with the intelligence that warrants his decision-
Unlike some rather amusing Japanese manuals. It is critical to ensure an
accurate T.D.C. The best way is with a spark plug dial gauge and a simple wire
pointer.
This also, ensures precise ignition timing. The strobe light is
preferred over the static method, as it takes up all the stack in the ignition
system.
This gives a more relevant on-road condition. The starter springs
in the housing need occasional replacing. Never grease them.
This only attracts
grit and renders the unit irreparable. Light oil and penetrating oil applied as
soon as you hear mis-start is the go. Spark plugs should be NGK, B9ES.. Champion
N2
or equivalent. Don't use. a warmer- plug or you risk holing a piston.
If you fowl these plugs, then you are riding too slow!
There is also a chance
of doing long term damage to the crank by lugging the motor all the time. I have
seen an SF2 with 100,000km's on the clock; the internals were in
excellent
condition, needing only a head job. Lining up T.D.C. for the tappets can also
be used for setting the points gap. Always start with the points attached directly
to
the backing plate. When doing the tappets, set them on the loose not too
tight. A bicycle spoke key fits perfectly on the tappet adjuster. Setting the
carbs determines whether
the ride is smooth or harsh and annoying. Setting
the slides on the top of the stroke gives reliable results. Take time to get it
right. The float bowls need regular cleaning in the
wet weather. Flushing
out the fuel balance tube occasionally, helps, as this is the lowest point of
the fuel system. The primary drive must be adjusted with the motor running.
If it is too loose, it will clank loudly against the case. To tight, and it will
scream in protest. Aim for the beginning of a faint whine. If it still clanks
loudly after this, then your
clutch rubbers have gone. A simple operation,
if you have bolts in the clutch drum. If not, you have to take out the drum (ARGHH!)
and replace the rivets with thread tap and
bolts. At least the rubber wears
and not the chain. The same applies to the cam chain, without the access hassles.
The small jockey roller on the cam chain and clutch rubbers
should easily
last12 months hard use. The motor encourages a mechanical empathy with the rider.
It attunes you to its needs before Catastrophe strikes SPECS Tappet clearance
Cold - inlet 0. 15mm, exhaust 0.20mm Contact breaker gap - 0.4 - 0.5mm Spark
Plug Gap - 0.6 - 0.8 mm Tick over speed - 800rpm
Wot! Another 750 article?
The Editors request was definite (1 couldn't worm my way out of it!)
Well,
most 750's have reached their 10th birthday and are possibly looking for that
little perk that will see them into the post classic era.
Of course, the
low production run for spare parts is reflected in the relative expense of some
parts- It shows the factory's commitment to supporting the best handling,
fine balanced bike they've ever made. Now that I've expressed my complete unbiased
------ Club member (Kiwi) Robin, recently came across an old problem with rebuilding
the 750 motor. That is: procuring the right hand side lay shaft bearing No.
NJ 303/C3- Or to put it more technically, the little one next to the gear box
sprocket. The critical point
is the C3 designation. This means that the bearing
runs very loose tolerances, probably due to the horizontal case. Although all
the bearings in the case run C3 clearance, this
particular one is extremely
difficult to procure if purchased through a bearing house. The only available
bearing is made by FAG and is available through CBC. A point to look
closely
at during an overhaul is the key way system. A point Tim Parker notes in his service
manual. (The only shortcoming in the design of the engine)- If the head starts
making
a tapping or knocking sound that you can't trace, it might be the cam
collars and key way system coming loose. This is more likely to happen on cams
that have been reground a
couple of times. Aside from devising a whole new
system, the only way to fix it is to have new collars machined up and heat shrunk
onto the cam tips. Knowing or finding a
competent machinist ( a rare bird
indeed) is invaluable. The key way system in the starter clutch should be checked
occasionally. If in doubt, replace the key. It is also a good
idea to oil
the starter springs and rollers while it's off. The starter chain stretches dramatically
after only a few starts but this doesn't warrant replacing unless completely stuffed.
Don't forget to fit a couple of small wire rods to the centre head stud under
the cam cover when reassembling. This ensures the studs can't block off the oil
galleries to the cams
and rockers. I can see all those 750's once again outnumbering
those 3 cylinder things almost 3 to 1 (dreaming!!!). Well it wasn't all that long
ago, there out there no doubt.
Those with an eye for fine machinery should
be able to pick one up fairly cheap, still I'm sure that won't last forever. I'm
sure many women would appreciate the low seat height,
combined with neutral
steering, low centre of gravity and, of course, "good vibrations". The 750 is
a bike over designed for longevity and designed also to be owner serviceable.
Bruce
To those who expressed interest in my Suzuki ignition mod for
the Laverda SF750, I hope the following is of help to you and addresses all your
questions.
The Suzuki ignition uses a mechanical advance (which is discarded),
not electronic, and the Laverda advance is still used. I did change the coils
to the type used on
Japanese bikes with electronic ignition. Mine are stamped
3210TR, can't tell the brand. I had the components in my garage from a wrecked
Suzuki GS650 (I'm sure other
early '80,s Suzis and Kwakas and Yams are similar)
and one day after destroying a set of points while trying to modify them to fit
the Laverda, I thought I would try the
Suzuki back plate on the bike, it
was close so I continued. This conversion would only be cheap, if, like me, you
can first get hold of the parts at the right price, new would
probably be
out of the question. The Suzuki backing plate that holds the triggers is a little
big, get it turned down to the same diameter as the Laverda points plate.
The inside rear of the Suzuki rotor needs to be machined slightly also, so that
it is a tight interference fit with the rear (circular part) of the Laverda points
cam, it will also need
to be shortened by about 4-6mm ( I forget), so that
it is in line with the pickups when mounted on the Laverda. That's it for the
machining. Mark the side that is going to face you,
of your newly modified
Suzi rotor where the actual trigger is and push it over the Lav cam (tight fit?),
leave the Laverda advance mechanism as is, then put it on the bike, place the
Suzi pickup plate in position, with the pickups horizontal looks best and lock
it temporarily somehow. Make sure there is an air gap at both sides when the rotor
passes the pickup.
The wires run nicely through the case ( If you are patient
you can pull the wires from the Suzuki plug and thread them through before pushing
them back into the plug,
(I cut and soldered) and up to the side of the fuse
box where you can plug into the Suzi ignitor. The ignitor mounting holes, I love
this bit, line up perfectly with the top air cleaner
to frame bolts, cool
hey! Bring the engine to top dead centre and rotate the rotor on the points cam
until the marked end is beside one pickup or the other. Wiring from Suzuki ignitor.
Black-white wire to earth Orange-white to +12volts (when ignition is on)
at fuse box Black-yellow to left coil neg. White to right coil neg. Now, remove
plugs from the cylinders, put
them back in their caps and earth them on the
motor, remove the right side case so as to see the timing marks. Use an inductive
timing light hooked up to either cylinder lead and use
the starter to spin
the motor. Adjust the rotor on the points cam (still moveable remember) to bring
the timing marks to the correct position. If the rotor to points cam is a tight
enough
fit you should be able to run the bike at this point. Then adjust the
timing so that maximum advance is achieved at the specified revs. You will probably
find that it is not idling at 0'
degrees, mine is a little advanced at idle,
don't worry just tune it accordingly, but make sure you are getting full advance!
When you are happy with the timing, mark the pickup plate
and the case, for
easy refitment. Remove the rotor and lock it onto the points cam (drill, tap,
loctite, grub screw), make sure it goes on square. Slot the Suzuki pickup plate
so you
have some room for fine timing adjustments. Put all parts back on the
bike (recheck air gap at rotor and both pickups) and recheck timing for maximum
advance and hopefully
Robert is your mothers brother. No more points! My
mod has been in service now for about 8000 trouble free kilometres, if the ignition
curve is changed in any way, perhaps from
the extra rotating mass of the
Suzuki rotor, it does not seem to upset it on the road. On rereading the above,
perhaps its not as easy as I said, but, if you follow the directions and
use
commonsense you will end up with a reliable, maintenance free ignition system,
perhaps even improve on it. If I can be of any further help with finer detail
to anyone with this just
email the list or direct to me. Ronny