Vintage Maico Clutches
by Avery Hensley, 2/2/99
The 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 parts.
-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 anything.
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 service life.
Before we break out the tools, let's try to gain a little understanding of how it was designed to work.
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 of.
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 problems.
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" clutch.
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, replacement parts.
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 handle.
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 plate rests.
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 stack.
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 obtain.
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 components.
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.)
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