|Vintage Maico Clutches
by Avery Hensley, 2/2/99
following information is primarily intended to apply to the “big”
clutch used on vintage Maicos, but will, in part, be applicable to the
“small” clutch, and possibly to other designs. This information
is provided in response to a couple of e-mail requests for assistance
in troubleshooting and repairing the “big” clutch, which
was originally designed and built by Maico for the 501cc engine, and
was subsequently provided on 400 and 440cc engines in the early 70’s.
This article does not attempt to include information regarding modifications
of this clutch, or conversion to later design components, but is primarily
intended to assist “big” clutch owners in using their existing
-Caution- Reading the following
information will expose you to potentially dangerous O.F.B’s.
(Old Fart’s Blatherings), that you may find totally ridiculous.
Please keep in mind that the author, a semi-literate lout, can only
tell it, like he sees it, and most certainly makes no claim to knowing
The problem: “I need
two more guys to help hold this %*##@&* Maico back while on the
starting line!!! Or “Seems to grind a little less if I push it
about 10 mph before putting it in gear”. Hmmmm, sounds like classic
first symptoms of a Maico clutch that has reached the limit of it’s
Before we break out the tools,
let’s try to gain a little understanding of how it was designed
First, let’s look at
the very basic, but somewhat deceivingly simple, vintage Maico primary
drive, clutch, and transmission design. It consists of a sprocket mounted
on the end of the crankshaft, with a primary drive chain transmitting
the engine’s power to the clutch which is mounted on the end of
the transmission input or “main” shaft. The transmission
provides four speeds, and uses a simple, two shaft layout. The “main”
shaft receives power from the clutch, the “lay” shaft, (when
in use), receives power from gears on the main shaft, and transmits
the power to the “sleeve pinion”, which is mounted back
on and rotates independently of, the main shaft, except when high gear
is selected. The sleeve pinion is splined (locked) to the front, final
drive sprocket, which provides power to the final drive chain. The drive
ratio through the transmission, in top gear is 1:1. In top gear, power
goes from the clutch, (on one end of the mainshaft) directly to the
other end of the mainshaft which is locked to the sleeve pinion and
therefore directly to the front, final drive sprocket. This basic design
is classified as a “direct drive” design transmission. The
direct design transmission is noted for it’s simplicity, and (to
my limited knowledge), has the highest mechanical efficiency rating
of any gear drive transmission.
Now that we have covered
the “basic, simple” stuff, (sure hope I got some parts of
it right), lets look at some of the “deceiving” parts. During
the late 60’s and through the 70’s, Maico was chastised
by various members of the print media, for using an “obsolete”,
“archaic”, “outdated”, primary drive chain.
At that time the average potential dirt bike buyer probably regarded
members of the print media as the “source of all good, modern
dirt bike knowledge”. The media correctly pointed out that a primary
drive chain required more maintenance than a gear drive system. Test
ride articles of the day usually criticized the primary chain, but interestingly
also normally praised the handling of the test Maico. Comments were,
in general, “really steers well”, “always seems to
end up on the inside line of corners”. Frame geometry and forks,
were analyzed and the usual conclusion was that there was some configuration
“magic” that enabled the Maico to steer so well. The Maico
did have good frame geometry and suspension, but a substantial part
of it’s steering “magic” was attributable to it’s
primary chain and transmission design. Simply stated and in comparison
to most other motorcycles of the day, Maico engines turned “backwards”.
This “backward” turning engine and clutch used the engine’s
“counter rotational” or “torque effect”, forces
to apply weight to the front wheel, especially during acceleration,
and therefore provided very good steering, while cornering. I never
had any “extra” riding skills, so I thought the little extra
maintenance required by the primary chain and clutch design, was a very
reasonable price to pay for steering that was noticeably more precise.
I really didn’t appreciate this little bit of design logic until
about 1971, when I made an attempt to create a “super” desert
rig 250. I obtained a pre-production F81M, 250cc engine from Kawasaki’s
R&D room and installed it in my 1969 Maico 125 chassis. I loved
the resulting motorcycle, and it was exactly what I needed at the time,
but it simply never steered like a Maico.
Another aspect of this simple
but deceiving design, is that the primary reduction ratio is less than
“other” comparable motorcycles. Simply stated, the clutch
and gearbox rotate at higher speed then “normal”. This adds
to your maintenance requirements, but there are some interesting benefits.
A Maico clutch and gearbox requires clean oil, that meets design requirements
(more about oil, later), or you will sustain accelerated wear and/or
failure. Be forewarned, that what works in “other” gearboxes
may cause some problems in a Maico. The higher than “normal”
speed of the Maico clutch and transmission allows them to be “small”,
(small = lightweight), but also requires that they be well maintained.
The “big” Maico clutch compares in size to a Honda Trail
100, and the gearbox is similar in size to a 50cc something or other.
They are very mechanically efficient, but yes, they are somewhat less
tolerant of worn or incorrectly installed parts. Again, interesting
compromises were made by the design engineers.
I know, I know, we still
haven’t fixed anything, and all you’ve seen so far, are
O.F.B’s, but there are still a few basics that we need to understand
about this deceivingly simple mechanism. I know it’s boring, but
I’m doing my best and believe it’s necessary to dispel a
few more historical “facts” that you may or may not be aware
I’ve sold, rode, maintained,
race prepped, and repaired a good number of vintage Maicos. Without
fail, when new or well maintained, the clutches worked well. They absolutely
did not slip, did not drag excessively, (you could always find neutral
and they did not creep on the starting line), and a normal rider could
easily pull in the clutch lever. When the “big” clutch was
introduced it was a little easier to pull in than the earlier “small”
clutch, and the hand strength required for either version was a bit
more than some other motorcycles, but was very reasonable. Most all
current vintage Maico owners probably have never seen or used a “new”,
“big” clutch unless they have overcome the results of “someone
else’s” wear and repair attempts. Generally, a vintage Maico
owner is lucky if he has duplicates of the original parts, installed
in the right place, and they are installed correctly. In other words,
most of the time you will need to verify that the clutch parts installed
in your vintage Maico are “the right ones”, and that they
are not worn out.
OK, now that we understand
some of the design compromises that were made, and conditions you will
find, lets look at the parts and pieces that can contribute to clutch
Yes, yes, I admit that I
got a little carried away in the previous paragraphs, and just couldn’t
resist including a substantial amount of OFB’s, (Old Fart’s
Blatherings). So, if anyone is still reading this, I’ll reward
you by trying to keep the BS to a minimum, and stay on the subject.
I’ll attempt to put into words the process I would use to troubleshoot
a dragging vintage Maico “big” clutch. All this verbage
may be boring, but I don’t have pictures to include so what you
see, is the best I can do.
First, take a look at the
clutch lever and perch, mounted on the handlebars. Is it correct, for
a vintage Maico? Has the clutch lever been bent so it prematurely hits
the handlebar? Many Asian controls were not designed to take in enough
cable, and yes, I have seen new clutch levers carefully customized (bent),
to make them easier to reach, that resulted in the complaint, “this
darn clutch drags”. Remember, your vintage Maico originally had
Magura controls, which worked, so check this out.
Is the clutch cable correct,
and well lubricated? I make my own cables because I learned that most
replacement Maico cables simply do not fit.
The cable is still installed,
so watch the actuating arm as you pull the clutch lever in a few times.
Does it look like the arm is positioned to provide movement through
the most usable part of the arc that it travels in? Is it possible that
the clutch actuating arm has been incorrectly positioned on the shaft
spline to make an incorrect cable fit??
At this point, I need to
define the terms I use to describe the various parts we need check out.
Clutch actuator arm and shaft
= The cable connects to the actuator arm, and the arm is splined to
the shaft. The shaft has a perpendicular slot milled into it, that form
the cam that pushes on the push pin. Push pin = The clutch “through
out” bearing, installed in the outer end of the clutch guide.
Clutch Basket = The largest single clutch component, includes the primary
chain sprocket and the kick starter ratchet is connected to it. Has
slots around it’s circumference that engage the tabs of the clutch
driving plates. The clutch basket mounts under, but rotates independently
of the clutch hub. Driving Plates = The plates with the largest outside
diameter. Their outside diameter has tabs, their inside diameter is
smooth. Original Maico driving plates were made of steel with a bonded
fiber lining. Barnett manufactured driving plates are aluminum, with
a bonded fiber lining. These plates receive power from the clutch basket
and provide power, through friction, to the driven plates. When the
clutch is engaged, (pulled in), these plates must not apply force to
any of the adjacent driven plates. Driven Plates = the smaller diameter
plates, made of steel. Outside diameter is smooth, inside diameter has
teeth that engage “grooves” on the clutch hub. Clutch Hub
= Mounts “inside” or “above” the clutch basket,
locked by spline to the transmission mainshaft. Receives power from
the driven plates, transmits power to the transmission. Clutch Guide
= Supports the stack of driving and driven plates. The top of the guide
incorporates the push pin and bearings, the bottom of the guide rests
on the clutch springs. Clutch Springs = Curved, spring steel washers.
When stacked together correctly for the clutch you have, act as a single,
lightweight spring, of correct height and pressure to make your clutch.
Reinforcement Plate = The top plate of the clutch plate stack. Locked
by spline to the clutch hub, positioned on the hub between 2 retaining
rings. There are a few other parts, and some slightly different clutches
that have been used, but I’m trying my best to describe the “big”
Whew, those descriptions
seem so simple when you thing about the individual parts, but when you
lump them all together, they look a bit complicated. I’m almost
sure I got a few of them right, but I’m depending on each of you
to correct me where I’m wrong. Painting these verbal pictures
is a struggle, for this two-finger typist.
If everything up to this
point seems OK, we are going to need to remove the clutch cover, so
lay the bike or engine on it’s right side, with the left side
of the engine close to level. If you need to change the oil, you can
drain it before you lay it over, but if you are careful, and the transmission
vent tube is kept above the level of the oil, you don’t have to
drain it. Relax, take your time, this won’t hurt at all. After
going through this a couple of times, and with a couple of helpful tools,
you will easily be able to disassemble a Maico clutch in 15 minutes
or less. You can take the clutch apart with the bike or engine upright,
but as you will learn, putting it back together almost mandates laying
it on it’s side.
Disconnect the clutch cable
and push back and forth on the actuator arm. The freeplay you are feeling
is a result of the clearance between the actuator shaft and the push
pin. Does it seem excessive?? If you don’t know, check it out.
There has been several different length push pins used through the various
years and models, are you sure you have the right one??
Remove the left foot peg,
(it should be the one on top), the kick start lever, and clutch cover
screws. Put a little forward pressure on the clutch arm while tapping
lightly with your screwdriver handle on the end of the K/S shaft, and
the cover should pop loose. The K/S shaft o-ring puts a little drag
on the shaft, so as you lift on the cover you will probably have to
push a few times on the end of the shaft, before you can lift the cover
off. The shaft needs to stay almost all the way in to keep it in position.
If you pull the shaft out too far you will hear a snap as the k/s return
spring unwinds, which is no big deal, but does mean that it will have
to be rewound and installed correctly. If the cover was installed correctly
there should be no need prying or pounding on anything.
Look at the top of the push
pin and the rearward edge of the actuator shaft “cam”. All
wear you see at these places, decreases the total amount of travel available
to make the clutch release. No adjustment will make up for this wear,
so be a bit critical. Yes, there are some modifications that can be
made to compensate for this wear, but correct new parts will perform
quite well. If your parts appear to have been modified, did the modification
compensate for the wear, without creating another problem?? Wear in
these areas becomes especially critical if you use Barnett clutch plates,
which we will discuss further down the page.
While your at it, take a
careful look at the k/s shaft bore hole in the clutch cover. The “big”
clutch required removal of almost too much of the supporting aluminum
around the hole. If your clutch cover has indications of the clutch
basket or chain rubbing or rattling around expect to eventually find
a longitudinal crack at the thinnest part of the aluminum boss. If the
crack extends outward, past where the o-ring rides, it is the source
of that relatively minor, but very annoying oil drip that you have been
intending to fix, one of these days. I haven’t had to repair one
of these cracked covers yet, but when we run out of uncracked clutch
covers we will have to come up with a solution. A weld repair in this
area could be easier, and more effective if the engine was converted
to the small clutch, because you could leave the cover thicker and stronger
where it is repaired.
Press on the primary chain,
about half way between the clutch and engine sprocket. If you have more
than about ¼ to 3/8” of slack, you probably need a new
primary chain. Look at the exterior of the ring that is brazed around
the clutch basket. If you find aluminum scuff marks, it indicates excessive
wear, and is probably the reason your clutch cover cracked, (if it is).
If you cover isn’t cracked yet, look upward with folded hands,
say “Thank you o powerful Gods that watch over vintage motorcycle
owners”, and FIX THE PROBLEM, or the next time you look you will
find the crack.
Now we’re ready to
disassemble the clutch, so you need to get your gear puller. My only
advice at this point is that if you don’t have a puller that fits
the clutch, measure the clutch, and go to your handy Sears, hardware,
or tool store, and get one NOW!! A very simple, inexpensive, screw type,
with two straight legs, of adequate height will work very well, AND
IS REQUIRED!! If you (or the previous owner) didn’t have a decent
puller, and have worked on the clutch, you have probably identified
the source of several clutch problems. A puller that is taller than
you think you need, is recommended. I also recommend that you get a
couple of 6” pieces of soft wire. Install the puller and slightly
depress the push pin. Just depress the push pin enough so you can move
the top retaining ring, AND NO MORE. Remove the top retaining ring,
and using the soft wire, temporarily tie the reinforcement plate and
the top driving plate to the bottom of the puller so they are up and
out of your way. Now you know why I recommended a tall puller. NEVER
release the pressure on the puller after you have removed only the top
retaining ring, or you will need at least two new (un-bent) steel driven
plates. So far, I haven’t successfully straightened bent plates,
so try not to bend them. Remove the 2nd retaining ring and carefully
release the pressure, and remove the puller. If your clutch parts are
not worn or bent too bad, you should be able to grasp the push pin and
with a few little wiggles, remove the clutch guide and all the clutch
plates in one stack. If it doesn’t work this way, look for causes
of binding as you remove the parts. Also, try to keep the clutch spring
stack, (under the guide) together, in the way they were installed. While
disassembling clutches I attempt to keep all parts together, in their
original relationship to each other, because I need to know if they
were installed correctly.
When you remove the Reinforcement
Plate (see definitions), pay particular attention to how it is installed.
If this is your first exposure to this clutch, and the Reinforcement
Plate appears to be installed upside down, it is probably installed
correctly!! If you inspect the Reinforcement Plate, you will note that
one side of the plate is machined, and the other side is not. Correctly
installed, the machined surface goes up, which places the un-machined
surface down, adjacent to the first driving plate. Yes, it looks backward,
but it must be installed this way or it won’t work. I’ve
never run across one, in use, that was installed upside down, but my
first thoughts indicate that the symptom would be severe clutch drag.
Clutch springs: I’ve
seen and heard all kinds of versions of how and why to change the stacking
sequence of Maico clutch springs. This article is about the “big”
clutch, so there is only one correct way to stack the springs, like
this: ()()()()()()()()()(), and only one correct number of springs,
and that is 20. If yours are not this way, they have been changed since
your bike left the factory. Please remember, it did work well, when
it was new. Since my first Maico clutch job in 1969, till now, I have
replaced (on the outside) about 10 individual spring segments (cupped
washers) because they had lost tension, which can easily be determined
by measurement. The height of each spring segment (cupped washer) when
new measured, at least .075” and should be replaced if it is less
than .070”. I have replaced many spring segments that were bent
or broken during installation, a few of which I damaged myself. Now
you know why I always install Maico clutches with the bike or engine
laying level, with the right side down. Yes, I have changed the number
of, and/or the stacking sequence, but in all of those cases it was because
I was using modified, wrong, excessively worn, repaired, or non original,
Remove the clutch spring
stack and now we can do a preliminary inspection of the hub, basket,
and their associated parts. If you experienced much binding while lifting
the guide and clutch plate stack out of the basket, we need to know
why. Assuming that the gearbox is in neutral, rotate the hub while watching
the basket. The hub must rotate freely in, and exert no drag on the
basket. If your basket wobbles about very much, something is wrong.
Grasp the basket, pull in and out to check the basket’s end play.
I would guess that you should have a minimum of about .010”, and
shouldn’t have more than about .025”. Carefully inspect
the clutch hub, look for scratches or nicks on it’s exterior that
would indicate someone has used pliers or a pipe wrench to hold it while
attempting to remove the clutch nut. If you find some marks, your hub
is probably bent. If you suspect something is wrong with the hub, use
a NEW, driven plate as a test instrument, and see if it slides, with
no binding on the hub, from top to bottom. Keep in mind, the previous
owner, after damaging the hub, probably had difficulty putting the clutch
back together, and may have spent time filing the teeth on the driven
plates so they appeared to fit. At this point, I must inject the following
rule: If you don’t have an appropriate tool for holding the clutch
hub while attempting to remove or tighten the clutch nut, STOP, and
take the time to make one NOW!! With a little scrounging for three old
driven plates, (I prefer the ones for the “small” clutch),
a scrap or two of appropriate metal, and a few minutes of welding, you
can have a tool that will do this job well, and minimal care, will last
for at least a few hundred years.
Inspect the clutch basket.
As stated earlier, if you have signs of anything rubbing on the basket
reinforcing ring brazed to it’s outer circumference, you probably
have some damage to the clutch cover, and also to the basket. At each
basket “finger” where the ring is brazed to it, squeeze
the reinforcing ring and basket finger together with your thumb and
finger. If you see oil appearing to squeeze out from between the two
pieces, the brazing has come loose, and must be repaired. The ring may
also be broken. Look at the slots where the driving plate tabs contact
the basket. Both edges of the slot was originally smooth and straight.
If yours are not, your basket is damaged. The driving edge of the slot
will generally have more wear then the “non-driving” edge.
Damage in this area, (looks like notches pounded into the edge of the
finger), always create clutch problems because the driving plate tabs
cannot slide freely in the slots. As this damage becomes worse, your
clutch will become harder and harder to pull in, and will suffer from
varying degrees of drag.
To make sure this article
is complete, I must now further expose my ignorance, and discuss the
differences between Barnett and the original Maico driving plates. All
I can do is share my experiences, and let you decide what is best, for
you. As you will see, I’m still learning.
I currently have two Maico
“big” clutches being exposed to racing service. These clutches
appear to be as identical as I can make them, and use identical clutch
levers, actuating arm and shafts and clutch covers. Both clutch baskets
and driven plate sets are in “new” condition. The only basic
difference between these two clutches, that I can identify to this point,
is that one uses new original equipment, steel driving plates, and the
other uses new Barnett aluminum plates. The bad news, (more about this
later), is that the clutch using the original steel plates, works great!
The other bad news, is that the clutch with the Barnett aluminum plates
has a few problems, that I hope I can correct. Simply stated, so far,
the Barnett clutch has excessive drag and does not “lock up”
as rapidly as the Maico clutch. I absolutely love one feature of the
Barnett aluminum plates, I don’t think the aluminum will “pound”
notches into edge of the basket slots as rapidly as the steel Maico
plates. I quickly learned that the Barnett plates require more freeplay
than the Maico plates because they appear to expand, with heat, more
than the Maico plates. With the Barnett plates and my normal technique
of adjusting freeplay to a minimum especially when I had excessive drag,
resulted in a slipping clutch after a couple of laps, and the subsequent
expenditure of funds to buy new parts for the second time, and I still
ended up with a Barnett clutch, with excessive drag. I’m currently
running the steel plate clutch, but I’m hoping to cure the excessive
drag with Barnett plates, because if at all possible I want to minimize
the wear on the clutch basket. If I’m successful with the Barnett
plates, I’ll brag about them, but as of now I’ll probably
be running the original steel plates. Another item that possibly contributes
to this problem concerns oil. Barnett, for years, and I’m sure
with ample justification, recommends ATF oil for their clutches. With
the higher than “normal” clutch and gearbox speeds, and
small, highly stressed vintage Maico components, I’m reluctant
to use ATF, because I have had many trouble free years with no accelerated
Maico wear, using Spectro and Bel Ray 80 wt. Gear lube. I may be forced
into trying ATF in an effort to solve my Barnett clutch problem, but
I will only do so after I have tried everything else.
Using your “genuine
Maico clutch hub holder”, remove the clutch nut. All original
clutch nuts (for the “big” clutch) that I have seen, were
made so they provided a perch of the correct height, for the clutch
springs. All original clutches also used an external tooth hardened
lock washer under the nut. If yours does not have a lock washer, the
clearance between your push pin and clutch actuator arm cam has been
increased by the thickness of the missing washer. I use the washer,
and red locktite to insure that the nut stays tight.
With the clutch nut and lock
washer removed, the clutch hub should easily lift off of the shaft,
and out of the basket. Between the bottom of the hub and the top of
the basket there should be a thrust washer. It is common for this thrust
washer to momentarily stick to the bottom of the hub from “oil
stiction”, and drop to the workshop floor if you are not careful..
I don’t have one in front of me to measure, so I’ll describe
it the best I can, from memory. The original one is about .080”(?)
thick, the top surface has a slight waffle pattern embossed into it.
The top side of the inside hole is chamfered, so it won’t grind
away at the radius transition on the bottom of the hub. If you don’t
find this thrust washer, and your basket end play was not excessive,
your clutch may not have had one when it was new. I’ve seen a
few that seemed to work correctly that didn’t have it, but most
of them do. There are two, stacked, needle bearings that fit over the
part of the hub that inserts into the bore of the basket. The needle
bearings usually stay inside the basket when you lift the hub, but sometimes
come out with the hub. Some small clutches, use a bronze bearing instead
of needle bearings, but all of the original big clutches I’ve
worked on, use needle bearings. Inspect the bearing surface of the hub,
the bearings, and the inside bore of the basket critically, especially
if you had excessive basket wobble or slop when you checked it.
With the hub, thrust washer,
and needle bearings removed, your basket can move toward the engine
sprocket, providing quite a bit of slack in the primary chain. The big
clutches were originally installed in the 501, 400’s, and 440’s.
I can’t address the 501 because I only worked on a couple of them,
so my comments are addressed to the 400 and 440. The 400’s and
440’s all came equipped with a three row primary chain, although
I hear that some owners are now using two single chains. Sounds reasonable
to me, but I haven’t done it yet, myself, so I can only offer
the following thoughts. I’ve never seen a broken three row chain,
but almost all that I’ve seen were well past their wear limit.
If running two single row chains saves a few bucks therefore allowing
you replace the primary when you should, it sounds like a great idea.
I will assume that your chain is a three row chain. The slack in the
chain provided by removal of the hub, thrust washer and bearings, should
allow you to carefully remove the basket and chain, by walking the chain
off of the engine sprocket. If you basket and chain comes off really
easily, your chain is probably worn out. With new chain and sprockets
you will probably need to remove and install the engine sprocket, chain,
and basket, together. Under the basket, on the transmission mainshaft,
is a another thrust washer. This thrust washer is .040” thick,
is made of hardened steel. and usually shows some wear on it’s
top surface. It’s purpose is to keep the basket from grinding
away at the parts below it. This washer can usually be turned over and
reused, if the top surface is worn enough to allow excessive basket
end play, but if it is worn excessively, should be replaced.
Inspect the basket internal
bearing surface, and the kickstarter ratchet mechanism and gear, on
the back of the basket, If the k/s ratchet gear has heavy wear, replace
it. When a tooth finally breaks off, you can bet that the broken bits
will run through the gearbox a few time, causing expensive damage. Remove
and inspect the k/s shaft and quadrant gear, looking closely at the
first or engagement gear tooth. When new, that first tooth was a bit
smaller then the tooth next to it, and it’s point was relatively
sharp. It did not appear to be hooked, , mashed, pounded flat, broken,
or chipped. If the first tooth seems to be flattened in any way, you
have discovered why, once in a while, your kickstarter seemed to lock
up. If the first tooth is bad, inspect the second tooth. If the second
tooth is sound, the first tooth can be carefully ground away so it will
no longer bind against the k/s ratchet gear, and the second tooth becomes
the first tooth. These k/s components are highly stressed, but have
a long service life, if correct starting procedures are used. I suggest
the following thoughts are appropriate. * - No mater what carb you use,
if your Maico doesn’t start, hot or cold, with maximum of 4 or
5 kicks, something is wrong, SO FIX IT. * - If your Maico has a cylinder
mounted compression release, ALWAYS USE IT WHEN STARTING YOUR MAICO.
The purpose of the compression release is to reduce the stress on the
k/s components. If you get frustrated, and feel the need to “kick”
something, use the nearest telephone pole or heavy duty truck bumper,
not your Maico kick starter. The first person to use the words “kick
starter” simply made a mistake, the word should have been “stroke
starter”. Learn to stroke your Maico to life, and it will reward
you with passionate, rushes of adrenaline every time you turn the loud
So let’s recap a bit.
You start at the top (the clutch lever and perch), and work your way
down to the last clutch component, the thrust washer under the basket.
You replace all excessively worn, incorrect or incorrectly installed,
or missing parts. You look for and replace all inappropriately installed
parts that seem to look OK, but were really designed for some other
model. (Remember that long actuator arms can make the clutch easier
to pull in, but reduce the amount of travel available to make your clutch
engage and disengage). We only modify parts AFTER we have confirmed
that the modification is absolutely necessary, confirm that it will
not cause other problems, and we are sure it will correct the problem
we started with. A possibly misunderstood modification case in point,
is welding up the clutch actuating shaft cam area. Replacing metal that
has been worn off, MAY help, but any extra metal added will result in
a shaft that cannot be installed in the case, or will effectively reduce
the amount of lift available from the cam. (you don’t need to
ask me how I learned this, but I was sure glad I had a good grinder
so the shaft could be returned to it’s original condition). I
must say, I’ve learned that it is far easier erase or move pencil
lines on paper, or more appropriately these days, computer lines on
screen, than it is to move or remove metal from a precious or expensive
part. Yes, I will continue to try things that aren’t in a book
somewhere, because I’m still learning. As parts become rare, we
will be forced to modify and/or learn to repair, what we have.
So, all that remains is to
correctly install all the parts previously removed. Like most repair
manuals, I’m going to cop out and say “simply reverse all
the above steps”.
In addition to having the
bike or engine laying with the left up, I also use a LITTLE heavy grease
to keep the spring stack in alignment, while installing the guide over
the springs. If any part doesn’t easily go together, something
is wrong, so find out what it is before you break or bend something.
If you suspect you have some wrong parts installed, call someone for
help in identifying what you have vs. what you need. Not long ago that’s
exactly what I had to do. I had new appearing but slipping “big”
clutch, (it had just been rebuilt by an unknown mechanic), with the
wrong clutch nut installed. The nut that had been used did not provide
a perch to space the spring stack, and I didn’t have a correct
nut available to use or measure so I could duplicate it. I called for,
and received greatly appreciated help, from Jeff Mullins and “Maico
Moe” in the S.F. Bay area, Frank at Vintage Maico, and Rick at
Northwest Maico. No one had the nut I needed, but everyone I talked
to did their best to provide me with dimensions, so I could make one.
Thanks to the help I received, the problem was easily corrected. My
hope is that this article will help someone and therefore reduce my
debt a little.
Now, my ignorance has been
fully exposed, so all readers know as little as I do. If you need some
measurements, or think I might shed some light on your specific problem,
drop me a line, I will try to help. I always welcome constructive criticism,
and have learned something from almost everyone I’ve run across,
so if you have any thoughts about these beasts, don’t hesitate
to share them. As stated before, I’m still learning. (and hope
I keep doing so for the rest of my life)
Yes, I confess, I confess,
I’m just a simple minded, semi-literate lout, but I’m also
a Maico Nut, so maybe you can cut me a little slack.
Authors Note: The primary reason there is so much confusion regarding
the "big" clutch, is because you can not find a source of
accurate information on all of the parts that you may have. Even though
I have been working on Maico clutches since 1969, and have about 15
various age Maicos scattered around in my workshop and storage shed,
I do not have, and probably have not seen, all versions of the "big"
clutch components that are being used. Everyone I’ve communicated
with regarding the big clutch, some who, like me, have been working
with it for a long time, has been very willing to share their thoughts,
and favorite recipe for making it work. Unfortunately, I have not run
into anyone yet, that has seen, and measured all of the parts you may
have. Therefore, many of the greatly appreciated, and very well intended,
tips and suggestions simply do not apply, to some of the combinations
of parts that are out there.
I would like to be able to
provide future readers accurate information they can use, to make their
"big" clutch work as good or better than it did when new,
and I’m continuing with this effort, but I need your help. I am
collecting accurate measurements of the critical parts, for the "big"
clutch, and will publish them as soon as these parts have all been identified.
The information we need,
("big" clutch only), is as follows:
How does your clutch work,
does it drag or slip, hard to pull, or work just fine?
Guide: Please measure the
height, from the top, machined surface of the plate that goes against
the first driving plate, to the top surface that the push pin balls
rest on. To measure the guide, I clamped a piece of tool steel to the
top of the guide, where the push pin balls are, and let the tool steel
overhang the cylindrical center part of the guide. I then measured the
distance from the tool steel to the surface where the first driving
Hub: Do the three slots in
the side of the hub extend all the way down to the surface that the
nut goes against? Does your assembly use a thick thrust washer, that
goes above the basket, and below the hub? Please measure the height
of the hub, from the bottom of the surface that goes against the basket,
to the bottom of the top (or outer) snap ring groove. I found it a little
difficult to get a reliable measurement of the hub, so I used the following
method. I clamped a piece of tool steel to the bottom of the hub, the
surface that goes against the basket, so it would overhang the grooved
sides. I installed the top snap ring on the hub, then measured the distance
from the tool steel to the bottom of the snap ring. Using this method,
I was able to get repeatable measurements that were all within .001".
Spring Stack spacer: How
long (or tall,or thick) is the spacer under your spring stack? Some
clutches use no spacer, some use the "big" nut that is partially
machined down so it acts as a perch for the springs and adds .750"
to the spring stack height, and some use a spacer on top of the spring
Spring Stack: How many springs
do you use, and how are they stacked together?
I'm also trying to come up
with some relatively simple test measurements, that tuners\owners could
use to identify potential problems with the parts combination they are
trying to use. I've come up with a method of measurement, and I'm trying
to settle on a recommendation for the "basket free play" and
"total available clutch free play" that tuners should try
To measure your "basket
free play", and "total available clutch free play":
1. Install the .040"
thrust washer, basket, bearings, and hub on the transmission shaft.
If used, install the thick thrust washer (smooth one side, waffle pattern
on the other), between the hub and basket, install and tighten the clutch
nut. 2. With the clutch nut tight, lift the basket, and feel the end
play. I suggest you should have a minimum of about .006", and a
maximum of about .018". If your end play does not fall within this
range, you should correct it. 3. Do not install the clutch springs.
4. Install the guide, all clutch plates, first snap ring, the reinforcement
plate, and the second snap ring. All parts should slide up and down,
freely. 5. With the guide and plate stack pushed all the way down, grasp
the sides of the push pin, (I use needle-nose pliers), and lift the
entire clutch stack until the plates and reinforcement plate contact
the bottom of the snap rings, and measure the total available movement
(I used a dial indicator). You should be measuring at the top of the
guide, not on the push pin. Push pin bearing clearance should not be
included in your free play measurement. 6. The movement you have is
the absolute maximum clutch free play you have available, with your
parts combination, regardless of how many and how you stack, the springs.
In use, you will not have this total available, because you do not want
to be able to make your guide bottom against the basket, and you will
probably reach spring-bind, with your springs. If your maximum available
clutch free play is less than about .100", I believe you will experience
varying degrees of clutch drag, no matter what you do with all other
What do you think of the
above test, and limits I'm suggesting as appropriate?
Clutch Plates: What is the
average thickness of your 6 driving plates? What is the average thickness
of your 5 driven plates?
Please send the above information
directly to me, Avery Hensley, firstname.lastname@example.org.
I realize that a request
for all of this information, probably classifies me as a huge "pain-in-the-butt",
but I simply don't know another way to gather the needed information.
I have never seen a service manual that provides complete, meaningful
information on this clutch, and I'm attempting to correct this problem.
All information I receive, will be freely shared with all interested
parties, via this excellent Maico Madness web site, with credit given
to all contributors.
Thanks for your help,
Avery Hensley email@example.com)
(Yeah, yeah, I’m just an old fart, now I’m a pain-in-the-butt,
but remember, I’M A MAICO NUT, and freely admitted that I’m
still learning, so maybe you can cut me a little slack.)