Clutch Question

Other than the obvious, what is the difference between wet and dry clutch.
My main concerns are clutch life, low speed and the friction zone, etc.

Thanks

 

Ted schreef:

Size.
Wet clutches can be built smaller because the oil cools the plates.
Drawback is that rubbed off friction stuff foules the oil.

As far as my experience goes, lifespan is not a problem for
both types, although a comparison of a BMW-R50 (35 horses)
with a dry clutch and a Kawa LTD-440 (55 horses) with a wet
clutch is not really a good comparison. Anyway, both types
never gave me any problem.
Oh.... Old oil tends to make the wet clutch sticky, so
that shifting into first gear becomes a problem. And it makes
the wet clutch slip, so that the engine revs more than it should.
But you renew the oil at regular intervals of course.

What you mean with 'low speed' and 'friction zone' is not
clear to me.

Rob.

 

With a wet clutch, some car oils can cause problems, and it's best to
use an oil made for bikes.

Leon

 

Leon schreef:

Many reactions on this group puzzle me. Like that B12 that is
supposed to be a wonder potion. Until recently I never heard
of it (I live in the Netherlands), and what is more: I never needed
such potion. Probably because I ride all seasons, almost every
day, so I never had a carburettor clogged up. Even though I once
had to leave my little Honda sitting still for 6 months outside at the
time my mother in law was hospitalized. When I returned home,
a single push on the starter button revived that Honda.
But then: It is a Honda after all.

As far as 'car oils' go: All those years I simply poored in 10W40
or 10W50 (don't care about the brand) in all of my bikes over the
43 year I drive myself. And I never have had any clutch problem.

Like the B20 potion: Oil made specifically for bikes? Never heard
of such stuff, don't know where to buy it, don't need it. This group
usually talks about vintage bikes. So use the (comparatively cheap)
standard oil, and forget about all the goodies (like: removes carbon,
lowers friction, adds horsepower) that oil companies talk about.
They usually talk shite to make you buy overpriced lubricant.

Rob.

 

Wet clutches are easier. Since they are bathed and therefore cooled by
engine oil you can slip the **** out of them and they won't overheat.

If you're looking at your basic street bike, a wet clutch is easier. But
it's not like dry clutches are hard--almost all cars have dry clutches.

On the whole, however, I can't imagine a situation where wet-v.-dry clutch
would ever be the decision point for a street bike. It's like deciding on
a bike based on where they put the choke lever.

Whatever it is you're trying to decide, you're over-thinking it.

 

By low speed, I mean maneuvering in a parking lot, such as turning around or
into a parking spot.

 

The dry clutch in the Bridgestone 350 GTR worked ok, but squawked on
engagement and rattled all the time. I prefer the oil-bath type.

 

Gene Cash schreef:

Oil certainly did change over the years.
Many years ago I owned a BMW-R20, vintage 1938. A single cilinder
200cc, supposed to put out a whopping 7 bhp. I once filled it with an
expensive oil. I forgot what brand it was.
And I lost almost all of them 7 horses. When I checked the cilinder,
cilinder head and piston, I found them totally clean. Turned out that
the oil had removed all carbon deposit. And thus (worn piston rings)
compression was almost zero. I fixed it by pooring a bit of cardan-oil
(SAE 90) into the spark plug hole. The bike smoked heavily for a while,
but the horses came back. From that moment on I decided to use the
cheapest 10W50 without additives I could buy.

I later sold that R20 to a friend of mine for 40 guilders (about 20
US$), because I then owned an R25 that I liked better.
Stupid me.
Some 20 years later I saw a beautifully restored R20, and asked the
owner how much it would cost if he ever selled it.
The guy looked me over and replied: "You can't afford it".

Rob.

 

Ted schreef:

Okay, I get it.

My experience: No difference.
Bikes weight, width of the handle bar, center of gravity, tire width,
tire pressure, wheel diameter, seat position and a miriad of other
things have more influence on maneuvering at low speed than
wet/dry clutch.

I also understand 'friction zone' now.
Again: no difference.

Experience:
Dry clutch: BMWs R20, R25, R50, R69, Ural (yeach!)
Wet clutch: Kawa LTD440, Honda VF400, Yam YZF-R6,
Suzi GT250. (was that wet? I forgot).

And many others I can't remember if they were dry or wet. (Salira,
Ardie, Panther, Triumph, Gilera, MZ, DKW, Horex, Harley and
more).
Don't tell me what type of clutch a Harley has, this one was a
single cilinder vintage 1927. All I remember is that it leaked
oil from everywhere, and you had to pump oil manually every
couple of miles. It had a hand operated gear shift (right hand
side of the tank), a foot-operated clutch, and a break lever at
the left hand side of the handle bar. That foot operated
clutch made a difference though. Someone push started
it once. When the engine picked up, he could not release
the clutch because he was running beside the bike.
So the bike took off and crushed a pram with baby to
a brick wall.
My father had a repair shop, I rode them in the fifties of the
last century as a child, before I ever got my drivers licence.
My dad pretended he did not know I took off with the bikes.
In hindsight, I know he loved me doing it.

Memories, memories.
Rob.

 

I've never worn a clutch out in 40 years of riding. Which is not to say
that I haven't damaged clutch baskets and center hubs from hard
shifting at high RPM and full throttle.

I got stuck riding a full dress Japanese touring motorcyle while trying
to find a camp site on a logging road in Oregon, I had to slip the
clutch endlessly to get over a small log and out of the rut. I thought
I'd fried the oil-cooled clutch because there was so much play in the
clutch cable, About five minutes later, the clutch had cooled off and
was back to normal.

Hooray for oil cooling. It works when you need it to work. My GSXR-750
has an oil-cooled clutch, but when my left arm gets tired, I shift it
clutchlessly...

So far as low speed operation and friction zone are concerned, that's
more a function of the clutch release mechanism.

Hydraulic clutches give the rider very little feel, so factory race
kits often replace the hydraulic clutch with a cable clutch. I hate the
dead-feeling hydraulic clutch release mechanism on my Yamaha, so I
tried my friend's race-kitted Yamaha and found that his cable clutch
also felt "dead".

But, theoretically speaking, a cable release system *should* give you
more feel when you're slipping the clutch around California DMV's
infamous motorcycle keyhole test...

If you're basing your decision on what to buy because of the California
test, just rent or borrow a small single-cylinder machine with a cable
clutch for one or two days.

Testy technical ramblings follow.

The major advantage of wet vs. dry clutches really isn't the cooling
media, oil vs. air. It's the diameter and surface area of many smaller
friction plates.

You could have a single plate air-cooled clutch like most stick shift
cars have, and, while you're driving down the road with the clutch
engaged, how is any air going to get between the pressure plate and the
clutch disk to cool anything?

Back in the early 1950's, the Jaguar factory built the XK series of
sportscars, and they were racing the "C" and "D" type open sportscars
at Le Mans. They had an interesting 9-inch diameter three-plate
air-cooled clutch that was capable of handling about 500 horsepower,
which was wonderful considering the car only had about 200 horsepower.

But the engine had to turn 6000 to 7000 RPM for long periods of time
and the engineers at Jaguar were worried about a 12-inch diameter
single plate clutch disintegrating at high RPM. The clutch also had to
endure the abuse of being slipped when starting out and
when the car was going around really slow corners.

Sportscar and dragracers in the USA didn't want to use specially built
multiplate clutches, they stuck to the single plate clutch and used
pressure plates with beefed up springs, and occasionally a large
diameter clutch or flywheel would explode.

And those parts were very close to the driver's private anatomy, so the
professional racers installed special scatter shields to catch the
flying stray parts.

I remember reading a bumper sticker on an Austin Healy Sprite that
said, "When I shifted at ten thousand, something flew out threw the
housing..."

I tore a segment of friction material off of the Chevrolet clutch plate
I was using with my
Jaguar pressure plate. What a bitch. The segment jammed to clutch full
engaged and I had to drive home on city streets to get to my garage and
pull the transmission out to fix the damned thing.

But this is a motorcycle NG, not a vintage sportscar NG. I learned
about both sportscars and motorcycles simultaneously, because the
writers of the sportscar magazines were also motorcycle enthusiasts
(like Gordon Jennings) who worked for the movie studios in their real
day job, and they reported on the advanced motorcycle grand prix
technology
that was being used in Europe

It seemed that the Italians and the Japanese knew how to build engines
that got their narrow band horsepower from very high RPM, and they
wanted to use 7-speed or
8-speed (or even more speeds) transmissions, but the British wanted to
use older single-cylinder engine designs and they wanted to limit the
number of speeds in the transmission to the same number that a street
motorcycle used, i.e., four speeds.

Now a street transmission has to have a very low first gear in order to
climb steep hills, and putter along an English country lane, but a
racing transmission needs a much taller first gear so the rider can
actually *use* all his gears on the race track. Using a low first gear
on the racetrack would almost stop the rider in the middle of the slow
corner.

So the Brits realized that they needed to slip their clutches furiously
on starting out and in slow corners, just like the drivers of modern
125cc go karts slip their clutches. Otherwise, it's unnecessary and
time consuming to use the clutch. You can actually fry your clutch on a
go kart if you use it when shifting gears.

A 125cc motocross rider was at a rider improvement school, and the
professional instructor told him, "I notice that you use the clutch
every time you shift gears." The new rider said, "Well, isn't that what
you're *supposed* to do?" The instructor said, "You don't have to use
the clutch except when you're starting and stopping."

That sounds like what the seller of a well-used Honda 250cc
square-fendered Dream was telling me when I first entered the
motorcycle scene in the middle of the 20th century...

 

You ought to be with the starving pygmies in New Guinea. (1)

The rider who needs to know about B-12 or similar carburetor cleaners
has never heard of it either, and has no real clear idea of how his
carburetor works.

So I spend some of my own time while waiting for better riding weather
to explain about cleaning and adjusting carburetors to help a newbie
who knows little or nothing about the subject, and what do long time
riders do?

They ridicule ME, the guy who's trying to help the newbie.

As Larry the Cable Guy says, "That ain't right."

(1) I can't help it if you've never heard of Larry the Cable Guy.

 

You should read better, or I should write more clearly (probably
the last is true).

I did *not* ridicule you. I did *not* ridicule newbies with clogged up
carburetors either. Tell you what, I have been a newbie myself.
There is even more; Even though I've been on a bike as long as
I can remember and grew up in the bike-shop my dad owned, I
still learn by reading this NG.

I wondered why so many drivers (US or UK?) seem to have clogged
up carburettors. That is a problem I never had, nor one of my friends
ever had. The difference between the number of clog-questions in
this NG and my experience even made me think that maybe (maybe)
there is a difference in the gasoline in The Netherlands and that
in the UK (US?). Your remedy always goes like: "use B12". You
most likely (I haven't experience with the stuff) are correct.

And then I also wondered what B12 is. I have never seen the stuff,
probably it is named different over here (such as 'carburettor
cleaner').

You are right on one thing: I never heard of Larry the Cable Guy.

I've been in New Guinea, part of my wifes family live over there,
I speak the common language, and have a Papua's underwear
in my cupboard (unused, never tried if it fits). But I never met a
pygmee in New Guinea.
They all live in Africa.

Don't wait for better weather, start your engine and enjoy.

Terima kasih.
Rob.

 

The average original purchaser of a new motorcycle in the USA does NOT
want to ride everyday. He wants to try something new that looks
exciting, so he buys a machine that he knows little or nothing about.
Maybe a friend owns one and he wants to hang out with his friend.

He does not HAVE TO ride everyday. He probably doesn't want to be seen
by the boss arriving at work on a motorcycle, because he would be
thought of as immature or unreliable.

He parks his motorcycle in the garage and takes his car to work as
there isn't a lot of public transportation here. A nice car impresses
the boss, as long as it doesn't cost more or look nicer than the boss's
car.

The average motorcycle rider buys a brand new motorcycle, rides it 5000
miles a year for the first year (if the wife lets him), then he rides
it less and less (if the wife lets him). His motorcycle riding buddy
thinks he's pussy whipped. He *is* pussy whipped.

If the motorcycle owner has a tolerant wife, he's a weekend warrior,
riding to some motorcycle hangout every Sunday and hanging out with
other weekend warriors.

If he's unlucky, his wife only lets him out for four hours on Sunday,
then he has to hurry home and escort her to the mall for serious
shopping.

The machine gets stored in the garage for longer and longer periods.
The gasoline evaporates, clogging the jets. At the same time, the
battery ages. The first time motorcycle owner may want to get his 4 or
5 year old machine running in order to get it out of the garage to make
room for his wife's heirloom discount department store "treasures".

Or maybe the original owner sacrifices the non-running machine and a
new owner gets the "bargain" of a second hand nightmare that won't
start.

I tell them where to start in this NG. I tell them about B-12 and the
fact the modern carburetors have no chokes and that they need to close
the throttle butterflies to make the carburetors suck, and sometimes I
tell them about sulfated batteries and corroded alternator cables and I
advise them to buy a maintenance free battery.

You probably get something similar across the pond. B-12 contains
toluene, methanol, acetone, 2-Butoxyethanol, Mixed Xylenes,
Isopropanol,and Methyl Ethyl Ketone.

The reason I suggest buying Berryman B-12 Chemtool Part Number #0116 is
that it comes in liguid (non-aerosol) form and can be easily measured
into a gas tank.

I have more than one toy, and many other things interest me besides
just the cars, trucks, and motorcycles.

 

Erm, BMW and Moto Guzzi have managed it for years.

Single-plate car-type clutches, both marques.

 

B-12 schreef:

<snip>

Clear story.
I'm getting old. Motorcycles used to be a means of transport
(and fun).
But nowadays many kids buy one only for fun.
Or to show off.
Currently it is the same over here, motorcycles disappear as
soon as autumn sets in, only to re-appear in the spring on sunny
weekends, most without a spouse on the pillion.

I now recall that my nextdoor neighbor always needed ages to start
his Faser. I never gave it any thought, but supposed he had a bad
bike. Must have been empty carburettors. Or fouled. Maybe both.
Nice weather, the weekend, a ride with a friend. That is what he did.
He sold the bike. Otherwise I would now go over and tell him to use
B-12. See? I'm still learning.

Rob.

 

One consequence though with airhead BMWs at
least is a need for occasional spline lubes which
are a mild PITA.

Not sure if this is something that could be avoided
by a beefier shaft or better lube arrangements.

 

B-12 schreef:

My bike has an hydraulic clutch. Can't say I miss 'feel' compared to
all the others with a cable operated clutch that I ever rode.
The only time(s) I missed 'feel' was when the cable frayed.
You say it yourself, that Yamaha felt "dead" both times.

What is the theory behind your remark. Sticky slave piston?

There you are. Like I stated before; unit size. And with that a
decision that manufacturers make. (What is in fashion + what forces
work on the bigger dry clutch if I create an engine that revs up to
15000 rpm). I bet if a car maker ever uses an engine that
has a red line at 17000, he'll fit it with a wet clutch.

If drivers should use the clutch where it is intended for (going off
in first gear and stopping --see below) it would not need cooling
because it would only slip (generate heat) when driving off. But
manufacturers need to make bikes fool-proof.

I've witnessed the desintegration of an overrevved flywheel on a JAP.
(I don't mean japanese, JAP was the bikes brand)
Like someone used a gatling gun. Nobody got hurt fortunately.

This is the basic thing. A clutch is only needed for riding away and
stopping.
I make it a habit to train myself in NOT using the clutch.
It was possible on all bikes I ever rode, although some are easier
than others. All low revving ones did not even need a clutch
when driving off, just a little push forward, switch in first gear,
(clack) open throtlle. Stopping is more cumbersome. You need
a fast moving left foot and right wrist. And a gearbox with a good feel
between second and first gear. But it can be done.

That Dream: Was that the one with that new japanese invention
they named 'rotary shift'? The one that went 1st gear down,
2nd up, 3rd up, 4th up, followed by 1st up (oops.... shake, rattle,
roll).

Rob.

 

Both, probably, but it's still got **** all to do with the clutch plates
overheating because of lack of airflow.

 

No, it wasn't.

 

Particularly if the clutch is fully engaged. Stop and go
traffic, maybe, but "driving down the road with the clutch
fully engaged" ? If the clutch is hot under those conditions
it seems like the engine and/or tranny are already fried.