1956 Turismo Rapido resurrection - MVAgusta.net
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post #1 of 22 (permalink) Old 09-04-2013, 04:22 PM Thread Starter
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1956 Turismo Rapido resurrection

Hello all,

Being new here, let me, by way of introduction, say that I have spent most of my life (and I am very old, over 50!) playing with a variety of old motorcycles. This is my first MV, but I have had other Italian bikes, among them my current Morini 3-1/2 (the most modern bike I have ever owned, being a mere 39 years old). I don't drive cars, and the TR is meant to be a daily, year-round, runabout to supplement the ailing BSA B31 currently filling that role for me.

I bought the TR about 6 years ago as a complete'ish non-runner, and quickly got it running. Terminal clutch slip, only slightly bettered by cleaning the plates and shimming the springs, was the most serious problem encountered, but everything else was pretty worn out as well, so the MV was put to one side awaiting another chance.

I don't know how much I can contribute to this forum, there not being much out of the ordinary working on bikes like this, but I shall try to at least offer a few observations in return for the questions I will no doubt have, and probably the occasional plea for elusive parts as well.

Waiting patiently for Jerry to check what engine parts the UK club spares stock may hold, I have focused on the chassis for now. But not before pressing the crank apart for a look-see. Up and down play could be felt in the rod, and I was curious to measure what it might actually be. It turned out to be around 0.08mm (3 thou), where textbook clearance for a ~25mm/1" crankpin is some 0.02-0,03mm/1 thou. A photo of the dismantled crank is at the bottom of this message.

Narrowly missing a NOS rod/big end assy on an Italian ad site, I set to investigating the options for what I had. Most of the wear was in the rollers and, while the crankpin was only very little worn, the rod eye (being part of the rod itself and not a replaceable ring) was - just - too oversize and oval to deal with just by replacing the rollers.

While bearing rollers in imperial (inch) sizes are freely available in oversizes for older engines (I try to make a living caring for Indians - the vintage American bikes - and I have bearing rollers in five .0005" steps in stock), making it easy to just hone the rod eye, or grind the pin, for the next oversize roller, the metric 5mm x 12mm rollers needed here frustratingly seems to be available only in the one size. And no near imperial sizes exist either. Making new custom rollers is possible, but would be a quite expensive and time consuming way of doing it, needing first turning to rough size, then heat treatment and finally grinding to final size. But, if more MV (or other) engines use the same size of rollers, there could be a niche here for an enterprising machinist (such rollers would be much cheaper in larger batches than just 20 at a time), making rebuilding these big ends easier. Case hardening depth of rod and pin is probably at least 0.5mm/.02", so there could be several goes in the stock parts. Just a thought.

The path of least resistance then seemed to be new 5mm x 12mm rollers, big end eye lightly honed back to round, and a new slightly stepped crankpin (I have a tame machinist routinely making such parts for me for Indian engines, and it will go to heat treatment together with a batch of these), with a small increase in diameter of the roller track, keeping the stock diameter at the ends to preserve the press fit in the flywheels. The very slightly increased length (in hundredths of mm/thousandths of an inch) of the roller path around the larger crankpin is so small compared to the diameter (5mm or ~3/16") of the rollers that I don't think they will even notice, even if theory may say that it could make them likelier to skid instead of roll. The 2 thrust washers were deemed reusable.

But back to the chassis. I have most of it pretty much under control, but will need new rear shocks. The present ones are obviously not right, in addition to being worn out. Now, being about as heavy as 2 or 3 tiny little starved postwar Italians, I would probably need - if I found a set - to beef up the springs of original shocks. Alternatively, come up with suitable modern replacements (e.g NJB or Hagon) of fitting length, complementary look and with a reasonable spring rate. Thus my first 2 questions:

1) Can anyone tell me the mounting bolt center-to center free length of original 1954-58 (and I am not sure they changed for a while after that) TR rear shock absorbers?

2) Can these be taken apart - in a non-destructive manner - for fettling and changing of springs?

As I am also a good bit taller than the aforementioned tiny little Italians, I shall move the seat back a bit (I will use a sprung saddle, as on the first TRs, rather than the very uncomfortable period aftermarket dual seat that came with the bike). This will have the useful side effect of putting more of my weight on the rear shocks, hopefully allowing me to keep the fork springs as they are, as they will only feel a smaller proportion of my greater weight, so to speak.

An observation, while we are at the front of the bike, is that the ends of the internal tubes on the forks that came with the bike were so hammered - presumably from bottoming out against the shoulder on the cast fork ends - that the bushing tubes could not be removed except by machining. Luckily I found a better set of forks, which even had nice sliders (mine had had water standing in them) and good enough to re-use bushings (mine were severely wallowed out). As an aside, while I have no way of knowing what year the replacement forks were, the top yoke and handlebar clamps are cast steel (or SG iron), while mine - 1956 - are aluminium alloy. Visually identical, otherwise.

To avoid the ends of the replacement fork tubes also being hammered by bottoming out, and as I can detect no bump stop function in this fork design, I decided to put 2 o-rings around the slider tubes before assembling the forks, to give at least a little cushioning effect on full compression. The o-rings are 28mm x 5mm; the 38mm OD fits nicely in the slider shrouds, and the centerline of the o-rings lines up nicely with the ends of the fixed tubes. I intend to lift the slider shrouds periodically to inspect the o-rings, and I can easily snip off one of them if 2 are too much. I guesstimated max fork travel to be around 110mm (not checking if the springs may become coil bound before that, though), so the combined, uncompressed, thickness of the o-rings steal just some 9% of the travel, and less when bottomed out over a big bump. Another pic of this should appear somewhere around here.

It may show in the photo that the shrouds (like most of the originally plated parts of the chassis) have been painted. There is a reason for that, beyond the hassle, expense and uncertain outcome of re-plating, and I shall get back to that another time.

Sorry about the long message!

Steen

PS: As this is going to be a little workhorse, an original portapacchi (luggage carrier) is high on my wish list, in case anyone should have one to spare. I could make up something, but not as neat as the original one.
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Last edited by Steen; 09-04-2013 at 07:58 PM. Reason: clarification
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post #2 of 22 (permalink) Old 09-06-2013, 12:16 PM
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Welcome to the forum Steen!
This is quite a heavy to digest intro indeed.
In all honesty I have no clue about the things You wrote.
But I'm sure there will be fellows here who can hold a candle on this matters.
On the other hand You seam to be a talented individual to tackle the issues.
So I hope Your little TR will be rolling soon and You have pictures of it.
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post #3 of 22 (permalink) Old 09-06-2013, 03:59 PM Thread Starter
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Thank you, Haupti.

Yes, I'm afraid my post got a bit dense. I wanted
to make a little contribution and not just the usual
"hey, I bought this kool old bike, tell me how to fix
it, awesome".

There is not much technical substance on most
old bike forums, and certainly not much in the
way of how to practically deal with fundamentals
like big end bearing rollers, which may not be
the most glamorous subject but without which
no bike will go anywhere. And about which I
happen to know a little. Sorry if it was a bit
much in one go.

What I was actually asking was not more tech-
nically challenging than if someone might be kind
enough to put their TR on its stand and measure
the distance between top and bottom shock bolt
centers.

For advanced MV mechanics, a bonus would be
if they would cast a glance at the top and bottom
of the shock shrouds to see if any split collets,
or other means of dismantling the shocks, might
be visible. And - just dreaming here - maybe
someone have actually had their shocks apart
and would be able to tell me if the bodies are
crimped/soldered shut, or would screw apart
for changing the oil seals and such.

Actually I have a fair idea of the stock shock
length, but it would be nice to have it confirmed.

Looking at factory promotion shots, the swing
arm seems to be horizontal in all of them. This
may just be an "artist's impression", but there
would be at least one mechanical justification
for doing it this way.

Assuming that owners will put the bike on its
stand when adjusting the chain, the swing
arm - with shocks thus fully extended - would
form a straight line between gearbox and rear
wheel sprockets.

This would be the point in the rear suspension
travel where the chain is at its tightest. So, if
our (possibly less than advanced, mechani-
cally) MV owner tightened the chain really
tight here, it would get no tighter - as all
other points of suspension travel would give
a looser chain; a function of the swing arm
pivot being some way behind the center
of the gearbox shaft carrying the sprocket -
and possibly bugger up the gearbox bearings.

So, trial fitting a couple of different lengths
of shock suggest that 300mm is too long
and 280mm too short. I have no 290mm
ones, but that seem to be the correct length.

IF the swing arm is indeed meant to be horizon-
tal at rest, and (big if) if the 57 year old fork
springs haven't sagged too much for this still
to be possible with the stock length rear shocks.

Sorry if I did it again! At least I have discovered
that you have to break the lines yourself.

Steen

PS: Seriously, if there is no interest here in tech
stuff I shall lay off with it. Lack of time will likely
spare you a full engine rebuild story, but I had
thought about mentioning a few details, like which
shaft nut is L/H thread, and which tool I used
for pulling the engine drive gear. But...

Last edited by Steen; 09-06-2013 at 04:01 PM. Reason: typo
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post #4 of 22 (permalink) Old 09-08-2013, 12:09 PM Thread Starter
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Thanks for the overwhelming response to my query
on the stock TR shock length.

Subsequent developments seem, however, to have
rendered the question somewhat moot.

Over the last years, I have tried to find as many
illustrations (factory and more recent) of TRs as
possible, and it looks to me like the designers of
the TR had a hard time of figuring out what hori-
zontal should be, and when (i.e. bike stationary,
or with rider compressing the suspension). Case
in point, the "speed lines" on the engine covers.

In some factory brochure illustrations, it seems
quite clear that, while the swing arm (as ment-
ioned earlier) is horizontal, bike unladen, the
engine cover lines slope forwards. Conversely.
with the rider on, the swing arm will tilt up to
the rear while cover lines come up nearer to
horizontal, so the two are still not in line. On
my bike, with too-long shocks and sagging fork
springs, this was even more (painfully) obvious.
And it doesn't do the rest of the visual design
justice.

Another point is how the bottom of the tank is
not parallel to either the cover lines or the swing
arm. It doesn't help in making the bike harmonious
to look at, but I guess it can be justified as a
means to wring every last drop from the 15 liter
tank. What were they thinking with this, btw?

At the brochure's 55Km/l mileage, you can go
over 800Km/600 miles on a tankful. Were BIG
tanks a sales point at the time? I would be happy
to trade half the capacity for a bit more steering
lock.

But back to my actual bike. See pic at the bottom
for details. Please disregard the temporary saddle
mounting.

The stance of the bike depends as well on how
much the fork springs have sagged over the years
(and I am not going to ask anyone to check the
original length of those!) as on the shock length.

I picked the longest pair of fork springs from the
two sets I had, but have no real way of knowing
how close they were to the original length. How
far up the front fender the tire disappeared at
rest, however, suggests that the springs are not
too bad. The pic shows my best guess at the
"static sag" (i.e. only the bike's own weight act-
ing on the springs) of the fork springs.

With the height of the front end of the bike set,
getting the bike level at rest was down to the
length of the rear shocks. This may sound un-
important but, being an Italian motorcycle, it
feels best when it looks good!

While I still think my 280mm test shocks may be
a bit shorter than the original ones, they gave a
nice stance to the bike. Swing arm slightly tilted
up at the rear (allowing me to tension the chain
to the max with the bike on the stand, with no
fear of it getting tighter anywhere during rear
suspension travel, thus rendering the gearbox
bearings safe from abuse), cover speed lines
near horizontal, and front and rear tires about
the same distance up into the fenders.

As the Koni test shocks are a bit inappropriate
for actual use (for one the springs are way too
hard, and they look too modern), I had a look
around for alternatives.

Hagon seemed to be the best bet. Not only are
they available in 280mm (and in 10mm increments
either side of this) length, they also have a lot of
different spring rates to choose from, as well as
the 12mm x 22mm bushings needed for the stock
shock bolts. These shocks are also available with
period-looking covers (indeed, I think that one TR,
prominently featured on this forum, might have
Hagon shocks, and looking very fine with them).

One important thing to watch with non-stock
shocks is of course that the fully compressed
length of them doesn't allow the tire to hit the
inside of the fender. With the slightly less than
3" travel of 280mm Hagons, this seems to be
OK, but I will check with a blob of modeling
clay on top of the tire (putting the bike on a
box, letting down the swing arm, blob of clay
on top of tire, raise swing arm until minimum
Hagon length between top/bottom shock bolts,
lower arm, inspect clay).

The appropriate rear shock spring rate is not
too hard to work out, and I am happy to see
that the (made for tiny little Italians) fork
springs don't seem to compress all that much
with me on the bike. So the taller handlebars,
putting the rider more upright (and also allow-
ing him a wider field of vision in traffic without
having to fit ugly mirrors), and saddle moved
back, seems to have worked insofar as more
of my greater weight is taken by the rear shock
springs (where it can be dealt with), leaving
the fork springs to feel only about the weight
they were designed for. If this turns out not
to work so well under dynamic conditions, I
can think of a few ways to deal with it. The
ultimate having new, harder, springs made.

Sorry if I have bored anyone to tears with all
this. Most of it is common sense/knowledge,
but you just don't see many instances when
people have taken the time to write it down.
So I - obviously being far from an MV expert,
but having a bit of all-round experience with
old bikes - thought I'd do so, in the vain hope
that it might help someone, somewhere.

Over and out.

Steen
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Last edited by Steen; 09-08-2013 at 12:28 PM. Reason: Clarification
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post #5 of 22 (permalink) Old 09-08-2013, 05:47 PM
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whilst you might not get a technical query reply, I love to read other's experiences of rebuilding and restoring/restomods.
It is refreshing to know that there are people out there who are old school enough to remake or modify parts. Please continue.
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post #6 of 22 (permalink) Old 09-21-2013, 06:33 PM Thread Starter
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Hello Revhead,

Glad you like it. "Restomods" is a new word to me, but
a good one!

Your comment made me wonder if I should have stated
my main point more clearly. Namely, that getting actively
involved with old motorcycles doesn't have to be rocket
science. Common sense, willingness to read and listen,
and a modest tool collection is all it takes. And a wish
to become more involved with your bike, of course.

Like the big end rollers I started with. I measured all
of that with cheap Chinese micrometers. Rule of thumb
clearances are freely available in any basic engine book,
and on tons of websites. So forming an opinion of how
badly worn your big end bearings may be is not all that
hard. If your engine needs this being looked at, you
can do this as well as anyone else (or maybe better,
as it is getting hard to find mechanics who can deal
with fundamental stuff like this, rather than compo-
nent swapping on modern bikes). Having the parts
repaired may not be possible at home, but you will
be in a position to instruct a general machinist how
to do it, and to judge if he did a good job or not.

However, there are lots of other angles than the
mechanical one to look at old bikes from. I mean that
in the most literal sense, having thrown out my TV
20 years ago, replacing it in front of the sofa with
at least one old bike at all times. I find it infinitely
more interesting to spend hours looking at these.

One angle of, perhaps particularly Italian, bikes that
most of us can appreciate is their visual design. Just
about all Italian bikes are pretty to the casual ob-
server, but they didn't end up that way by accident.

It is a good idea to keep in mind that all design, be it
mechanical, visual or otherwise, is the result of some-
one having made some choices. Atoms don't fall into
line, making up good looking motorcycles, by them-
selves.

Looking at the little TR side on, two things had me
scratching my head a bit. Why isn't the seam on the
toolbox parallel to the frame tube next to it, and why
is the logo on the engine placed where it is? (a bit back
from the middle of the front/back length of the cases)

The crank shaft on the TR is placed fairly accurately
at the mid point of the wheel base. A natural (and,
indeed, common on other bikes) place to put the logo
on the engine covers would have been over the ends
of the crank shaft, sort of emphasizing the mechanical
center of the engine. An alternative logical placement
could have been the mid point of the cover, if for no
other reason than eye pleasing symmetry.

The first attached pic is of a TRE, but the toolbox
(and most of the rest of the bike) is the same as a
TR. The seam of the toolbox not being parallel to the
adjacent frame tube is clear to see.

Architects (the ranks of which industrial designers
were typically recruited from before there were
schools specifically for this) have a notion that
things of a different nature should be kept distinct.
They have a whole bag of tricks for this. Color is
one of them, and lining things up or not is another.

So, one possible clue was that a toolbox is of a
different nature and purpose than a frame tube.
That could explain why the, presumably classically
educated, architect behind the design couldn't
bring himself to make them parallel. But it didn't
explain why either had the angle it did. So I drew
a line through the seam on the toolbox. The
opposite angle suddenly jumped out as the
center line of the cylinder. See pic 2.

And the logo suddenly fell into place where
it sat. So the reason for placing the logo
where it is seems to be that the person in
charge of the visual design on the bike de-
cided that the cylinder axis was more visual
important than the center of the crank shaft
(makes sense with the clean, rounded covers
that - as opposed to "tight" modern engine
design where the exterior closely mimics the
engine internals - de-emphasizes the mecha-
nical bits within), and then needing a counter-
point to this angle. As the seam of the tool-
box is more visible in real life than in photos,
with the light reflecting from it, this might
have seemed a good counterpart for the line
through the cylinder axis.

Having these two major lines of the side-on
view of the bike (and, incidentally, suggesting
that this was indeed the main view the designer
worked with on his drawing board), suddenly
locks the logo into the only place it could logi-
cally be.

It is probably also not just coincidence that
the line through the cylinder axis points to
the tank logo.

If anyone is still awake, I would like to touch
upon another aspect of why I find the TR so
interesting. Trying to place it in a historical
context, and the way history can work on
different, sometimes sort of parallel, levels
(I'll try to make it brief!).

As I mentioned earlier, my main bike is a BSA
B31 from 1954. A very traditional British bike
with its roots firmly planted in the 1930s.

While solid and reliable, it is also heavy (180
Kg or some 400 lbs), which makes it a bit of a
handful on snow and ice, and has a number of
functional drawbacks. Yes, it is also ridiculously
slow by modern standards, but I don't mind
that. One of the drawbacks is that the oil
is in 3 compartments. Oil tank for the engine,
gearbox and primary cover. The engine oil
fairly quickly gets up to operating tempera-
ture, but the oil in the gearbox needs really
long trips before it - if it ever does - gets up
to a temperature that will boil off the water
that has condensed in the gearbox. Thus,
within days of being changed, the gearbox
oil looks like mayonnaise. More or less the
same with the primary.

I don't imagine that the average BSA owner
of the mid 1950s would have thought much
about these details, but he would certainly
have been attracted to the modern, actually
designed after the war, designs that started
coming on the market at that time. Like the
MV TR.

Here was a bike that weighed half as much
as the BSA and its ilk, was plenty fast enough
for gentle commuting, very economical, and
where oil was shared between all engine/
transmission components, and only needed
checking/draining/filling at one point instead
of 3 -and (if our man was a gearhead) where
all of it was brought up to operating temper-
ature together, boiling off condensed water
before it turned the oil into yellow goo.

The point I am trying to make here is that I
find it hugely amusing to actually relive history
in such a personal way. Riding old bikes be-
cause they are cool is fine, but experiencing
the actual feelings - and for the same reasons -
that made 1956 BSA Man think of changing to
something more modern from the continent is
getting personal with your old bike on a higher
level.

Steen
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Last edited by Steen; 09-21-2013 at 07:11 PM. Reason: Clarification
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post #7 of 22 (permalink) Old 09-23-2013, 10:26 AM
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Steen, I can take that measurement for you tonight for what it's worth....
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post #8 of 22 (permalink) Old 09-23-2013, 05:46 PM
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Keep it coming please.
That toolbox seam line would irritate me to the point of modification!
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post #9 of 22 (permalink) Old 09-23-2013, 05:55 PM Thread Starter
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Yes, thanks, that would be interesting. If nothing
else "for the record".
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post #10 of 22 (permalink) Old 09-23-2013, 06:02 PM Thread Starter
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Prior reply meant for Sheriff...

Revhead, yeah, but what if irritations like this
turn out to be a deliberate and central part of
the original designer's intent? Should they still
be modified just because we didn't get the point?

Speaking of which, another minor mystery that
has puzzled me a bit.

The operating arm on the rear brake plate seems
to be pointing downwards in factory illustrations,
and on most current examples (except I think the
Sheriff's is pointing up?).

The original setup has the unfortunate side effect
that the brake rod, between operating arm and
pedal, fouls the frame bracket for the passenger
foot peg. You can see in many pictures that the
rod has been bent to minimize rubbing contact.

Why did they do this? (no, I don't have an answer!)
With the arm pointing up, the rod doesn't rub on
the frame bracket, but I am not sure if it will rub
on the shock. This feels a bit odd, as I think all
the parts were designed specifically for the TR.

Steen
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