clunking when shifting gears

I own a 82 440ltd, kaw and when I shift there's a pretty good clunking
noise. just wondering if anyone has any idea if that's not good. I've
owned the bike for about 4 months and it's always done it.
thanks for you help

 

Usually present on much larger engines(with much larger transmiss-
ions), I'm surprised of this. However, I really wouldn't worry too
much about it. You don't describe how big the "clunk" is, or if it's
every gear change. But, if it does happen for every change, and/or
other motorists or pedestrians are turning their heads, or seeking
immediate shelter, you might want to have the dealer take a look.

Gary

 

I should have commented on the initial post but...

From what I've seen in books, motorcycle transmissions don't
have "synchronizers", so some sort of "clunking" is probably to be
expected -- the shift mechanism has to flick from one gear to another
rather rapidly; in particular, there should be a complete disconnect
from one gear before engaging the next gear.

Automotive synchro's are conical friction surfaces, which engage
/before/ the toothed ring, using friction to speed-up/slow-down the
toothed ring to match the teeth on the target gear.

I'm a relative newbie (and given that my Vespa is a CVT design,
really not experienced with cycle manuals), but my first thought would
be to check the clutch action. Put the bike up on the center stand, and
ensure that the rear tire doesn't rotate when holding the clutch in
fully, in any gear. If the clutch isn't releasing fully, there may be a
touch too much pressure on the engine side of the transmission for a
quick/smooth gear change.

--

 

Hi,

My $0.02 on this one.....

OIL - OIL - OIL - (not to start an oil thread please)

The viscosity of the oil and / or the "dirt" in the oil - (or any
combination of the above) MAY cause the clutch things to hang when you
shift - what I would do is change the oil (filter too) and use the
recommended weight of oil for your cycle.

( IMHO-changing mine from a multi 50W to a multi 40W helped a lot)

Another thing - is HOW you shift....

You may be doing - - Accelerate - clutch in - shift - clutch out - go

You may want to try - Accelerate - clutch in -PAUSE - shift - clutch out -
go

The PAUSE may allow things to catch up.... try it - YMMV

Hope this helps . .

Take care -

John b - Wisconsin Cheesehead

 

This might seem somewhat counter intuitive but has been true for my 4
Yamahas. Clunky gear shifting (while under way) can be caused by a
clutch that disengages too far. When I get a bit more clunky shifts than
usual, I will check if it is possible to put a bit more slack in the clutch
mechanism without causing other trouble.
If there is too much slack in the clutch, you get crunchy, scrapy shifting
rather than clunks.

Another thing I have noted is that you should not take a long time to
change gear. Start applying pressure on the shifter just as the clutch is
fully disengaged and then keep pressing it and start engaging the
clutch again immediately. Even if the wet clutch ensures that there is
always some movement in the gearbox, it seems to benefit from not
slowing down at all.

If you think about it, both of the above points are really the same.

 

Thanks all for the idea's which I'll look into I'm gonna start with my
clutch pulling habits then look into the oil change.

 

I've had the chance to put several hundred very enjoyable miles on a
76 BMW 600. BMW boxers have a dry clutch that, like you say, releases
more completely than a wet clutch.

Like most bikes and cars the BMW trans is "constant mesh" so each
gear spins at the rpm appropriate for rear-wheel/road-speed all the
time. So to accomplish a shift the input shaft and the clutch disk
must be brought up/down to the "right" rpm for the rear wheel speed
nearly instantly. BMW also has an input gear reduction, so the clutch
disk is spinning even faster than any gear. Shifts between the upper
(closer) ratios are pretty smooth. Between first and second it will
clunk ferociously, unless I let the clutch out in neutral and match
revs to effect a true "double clutch." The 2-3 shift can be mighty
clunky, and all the BMW riders I've talked to basically say shift
quick and positively.
Strangely the BMW and my old Yamaha 850 both seem to clunk less when
revved up more.

There are some interesting articles about the BMW transmission, and
how it was designed and maybe made by ZF. There are discussions about
the clunkiness in part being caused by the relatively small clearance
between the engagement dogs and pockets.

ZF also made the famous 4HP-22 (BMW/Volvo/Jag/Peugeot automatic),
whose early versions when slightly used developed a small internal
leak that left various clutches engaged, allowing them to be destroyed
in a few minutes by revving in neutral or park, like during emissions
testing, and a recent Corvette transmission that needs to have its
exotic lube changed frequently, partly to keep the synchro bronze wear
debris from reaching harmful levels.

 

If the transmission clunks disagreeably, you must not
be wearing earplugs.

 

snip

Actually cars do not use constant mesh transmisions, they use syncromesh.
b

 

And that is supposed to mean ? Just asking because as it's a new
term to me (not being a native English speaker).
Anyway, they are still constant mesh (well, reverse isn't, is it ?), even if
they
are something more as well.

 

What's the difference? I've seen both terms used to refer to modern
transmissions where the gears are constantly meshed and gear selection
is vis syncro rings that slide on splined shafts to engage the
appropriate gear to the shaft.


Matt

 

Not since 1909. http://www.cotta.com/history.html

Every modern car and truck manual that I've ever seen has had constant
mesh gears. The biggest change was the addition of synchronization,
which most cars and trucks have, but I don't think is present on most
motorcycles.


Matt

 

To eliminate the noise developed in the old spur-tooth type of gears
used in the sliding gear transmission, the automotive manufacturers
developed the constant-mesh transmission that contains helical gears.
In this type of transmission, certain countershaft gears are
constantly in mesh with the main shaft gears. The main shaft meshing
gears are arranged so that they cannot move endwise. They are
supported by roller bearings that allow them to rotate independently
of the main shaft. Constant-mesh gears are seldom used for all
speeds. Common practice is to use such gears for the higher gears,
with sliding gears for first and reverse speeds, or for reverse only.

The synchromesh transmission is a type of constant-mesh transmission.
It synchronizes the speeds of mating parts before they engage to allow
the selection of gears without their clashing. It employs a
combination metal-to-metal friction cone clutch and a dog or gear
positive clutch. These clutches allow the main drive gear and
second-speed main shaft gear to engage with the transmission main
shaft. The friction cone clutch engages first, bringing the driving
and driven members to the same speed, after which the dog clutch
engages easily without clashing. This process is accomplished in one
continuous operation when the driver declutches and moves the control
lever in the usual manner. The construction of synchromesh
transmissions varies somewhat with different manufacturers, but the
principle is the same in all. As is with constant mesh transmission,
typically first and reverse are not synchromeshed either (in some
cases you may find a synchromeshed first gear, but never reverse as
far as I have heard).

 

On the manual transmission cars I've experienced, reverse seems
to be handled by swinging a straight-spur (hence the whine) cog in and
out of position (not sliding along the gear axis, but perpendicular).

However, I've never seen an unsynchronized first gear. It is
sometimes a pain to get into first on a cold transmission after
starting, but that is more because the thick oil has "frozen" the drive
train, and first has the greatest relative speed difference -- flicking
the lever through the other gear positions from high down tends to free
things up. It also positions the synchro friction ring to make contact
before the toothed ring (the transmissions I've studied use a "two-part"
synchro -- the inner friction ring, and an outer toothed ring; ideally
the inner ring extends out to the side of the target gear so it makes
first contact, then the outer ring slides over the inner ring before
reaching the teeth. This "slide" positions the inner ring to protrude
from the back side, in preparation for shifting to the adjacent gear.
And is why going from a gear to neutral and back sometimes takes effort
-- the friction ring, not having been pushed to the adjacent gear, is
out of position for re-engaging the original gear).

--

 

No... At least not in the last 40 years.

The gears, proper, are in constant mesh, on free-running
bearings. The gears have a ring to the side with teeth and a cone. The
synchronizer is splined to the shaft.

The synchro consists of an inner friction ring (hollow double
ended cone) with teeth on the outside edges and splined to the shaft,
and an outer ring, with detents to the inner, to which the shift linkage
connects.

To engage a gear, the linkage pushes (let's say left and right)
the outer ring to the left. The detent pushes the inner ring. The inner
ring friction surface meets with the gear cone, bringing the two parts
to the same speed (the gear is free-running, the friction ring is driven
by the shaft). As you continue pushing the shifter, the outer ring rides
over the detent, until its splines/internal teeth, slide over the teeth
of the friction ring, and subsequently over the teeth of the gear ring
-- this action locks the gear to the friction ring, with the friction
ring locked to the shaft. It also has slid the outer ring to the second
detent position wherein the friction ring is protruding from the right
side.

To shift to the next gear, the linkage pulls the outer ring to
the right. When the outer ring disengages from the gear ring, the system
is in neutral. Continuing the shift, the friction ring makes contact on
the right side gear cone, etc.

You may have noticed -- the synchronizer is shared between two
gears (left and right). This is why the H pattern of an automotive
shifter. The left vertical of the H handles one synchronizer, to get to
the additional gears you have to leave that synchro in neutral and
activate a different linkage for the next vertical of the H.

Sequential transmissions (motorcycle) pack all the gears against
each other -- no gap for a synchronizer between pairs. Instead, they
move a rod with teeth (one gear wide) through the shaft of the
free-running gears. The inside of the gears are toothed. Shifting
involves pushing/pulling this toothed rod from engaging one gear to the
next adjacent gear -- the rod will only move during that short interval
when the inner teeth of both gears are in alignment. It is the toothed
rod which transfers rotation to the shaft.

--

 

This is an extremely rare system in modern motorcycle gear
boxes. The normal system is actually quite close to the one that
has been described for cars in this thread, the difference being
that there are no friction cones to synchronise things and the
dainty splines that lock the freewheeling gears to the sliding parts
are replaced by crude "dogs" and holes.
I know I'm not getting this explanation very clear. Why don't
all of you who hasn't got a clue about motorcycle gear boxes
go read a book or visit a few web sites on the subject.

 

Probably skilled double-clutchers -- slide into neutral, let out
clutch, blip engine, push clutch, drop into first... The trick being to
match the driven side to the speed of the free first.

Don't really need the clutch to go out a gear, just to let the
synchro work going into a gear.
--

 

That isn't what you said above. You said the gears, plural, not the
reverse gear.


Matt

 

Doesn't take a genius at all, just a fairly simple technique called
double-clutching. Drop from second gear into neutral. Engage the
clutch and blip the throttle up to a few hundred RPM above the speed the
engine will be in once in first gear (it takes a little experience to
know what RPM this will be at the various speeds from say 2 to 20 MPH).
Now depress the clutch pedal again and shift into 1st gear. Done
correctly, you will have virtually no gear clash at all. Most large
trucks (at least 25 years ago when I was driving them) don't have
synchronizers and double clutching is standard practice when
downshifting. Usually you can upshift without double clutching, but
some folks double clutch both directions.


Matt

 

After driving OTR trucks for several years, I still double-clutch even
with synchromesh transmissions. Makes for a smoother downshift and my
synchro friction material will last forever!

Also, my Chevy pickup has the granny low gear and it is so much lower
than second (labeled 1st on the shifter), that if you don't
double-clutch it takes forever to get L to engage. I can double-clutch
and drop it into L at up to probably 15 MPH.


Matt