Some sachs clutch modifications

I got a few sachs engines. I'm going to share my experience with the manual clutches first and then give some tips on improving the automatics. This applies to 504's and 505's and assumes you have the standard 2-pad/3-plate clutch

Manual clutch

my bike runs a 2 speed manual and I had a load of trouble with clutch slipping. Then I got some milled pads and plates, the german super clutches.

only problem is they're super expensive and you cant get em shipped stateside so you gotta know someone over that side of the pond.

They rip. no slip. if i revved it and dropped the clutch, it'd pull a backflip out from under me.

anyhow i wanted to share about em, they wouldn't be too bad to replicate.

New "uber" pads [#18], 2.15mmx4

plate [#16] 1.7mmx5

17.1 (meas 17.3) total thickness

plus it has a stiffer base spring [#20]

old pad 3.2x2

plate 1.7x3 (on an standard 2 pad automatic clutch you get one 1.7mm plate and 2 2.6mm plates, the 2 pad manuals have three 1.7mm plates)

spacer [#15] 4.5mm

16mm total thickness

and on the manual clutch you also have 3 15.8mm (3mm diam) pins [#14]

If you find any second clutch pack even from an automatic, grinding down the clutch pads is all you'd need to do. 1.7mm plates should

be thin enough as-is, the manual's already have 3 and the automatics usually have 1. Pads are easier to grind too. I'd grind the side where the oil channels don't go all the way out the teeth, you'll see what I mean looking at em, so that you dont loose oil turbulence. it'd be important to keep the 2 sides absolutely parallel too

Once it's all down to those uber clutch sizes though, it still doesnt quite fit. You can mill the bottom spacer [#21], theres a lot of room for more clutch to fit in the bell, but the spacer pushes it out. that’d be best. You also have to ditch the spacer [#15] on the end.

or another option, instead of milling down #21 you can space out the cover. if you just flip the inner spacer [21] and get rid of the outer spacer [15]it buys you enough room to fit it all in the bell, BUT it pushes the engagement bell piece [#11] too far out so the clutch cover disengages the clutch when it’s tightened on. a few extra gaskets or a custom spacer works. So either you gotta mill down #21 about .5mm or flip it and add some extra gaskets on the clutch cover. I did the latter and have 3 clutch cover gaskets.

problem 2, the new uber clutch pack is too thick for the old pins. the clutch disengages when you pull it by pressing the set of 3 pins [14] thru to push the back plate and spring [16,20]. The pins are only 15.8mm which works because the normal outer spacer [15] is recessed. with the new setup at 17 thick, you need longer pins. i found some (3mm diameter 18mm long) from McMaster Carr. they work, I have a ton extra. now if you want some, they’d be free.

so. longer pins, flipped inner spacer, no outer spacer and a few extra gaskets for the cover, and it works. I run a belray gearsaver 85w gear oil. Tried everything down to ATF with no change, and sachs recommends 90w for it’s manual tranny bikes.

I also put a little whirly piece to whip the oil around and keep everything lubed and cool. that's equally or more important than friction area. it's just a cut piece of tin can with bent out tabs bolted in there. pins go through it. i havent any pics but get creative.

Automatic Clutch

For you normal automatic folks:

This is an Automatic sachs clutch. I took parts from two standard 2-pad/3-plate clutches. milled the pads to fit 3 pads and 4 plates for more friction area and less slip. The 2 center plates are the thinner 1.7 (usually one in each clutchpack is this size), outer 2 plates are standard 2.6mm thickness. pads are milled down to 2.3 from 3.4mm. Also good to recut the oil channels in the pads. After that you just have to add shims to make sure the center toothed piece [#19 above] has proper clearance so it grabs only as the donut springs out or the starter bell is pulled in. ready to rip.

The other big problem people have with the sachs auto clutches is the nut backing off the end. the reason for that is that the clutch only attaches to the crank by the nut on the end, whereas most clutches are taper fit so they really get snug on there. That means the sachs clutch can spin the nut free, basically because the clutch can spin freely from the crank if the nut gets any loose. Taper would be ideal, a woodruff key would be great but neither are really easily doable.

What I did was to take the toothy bit [#19]and drilled and tapped a 1/8 in. hole through the side of it and then got a short allen set screw for it.

-somethin like that.

I lined it up on the crank and drilled a tiny divit into the crank where it would sit normally, making sure that's alligned right. Then drilled a big hole in the top of the clutch case to get to the screw and tighten it down through the slits in the side of the bell once the bell and spring and evrything behind #19 was in place. Then i just put a cover over the top hole, theres no pressure on it, just to hold the oil in.

Assembled the rest as usual. Red loctite on the end nut is

still a good idea. clean it with brake parts cleaner 1st to get any

oil off.

Hope all this info can be of use to someone else.

Re: Some sachs clutch modifications

Nicholas Dynan /

Awesome post, I just put a 3/4 setup in my 505D. Need to reread you the nut part to understand but lots of good info!

Re: Some sachs clutch modifications

Can you make an automatic clutch into a 2 speed manual function?

How Expensive?

Re: Some sachs clutch modifications

Nice dude. I will have to read more into this post later when I have more time. Thanks for the ideas. Been working on my Sachs a lot lately. Hopefully it will be running by the end of the weekend although this post probably just made a lot more work for me.

Do you think its worth it to modify the clutch on a stockish setup? Also, here did you get more plates, can you buy them or must I harvest them from my other engine?

Re: Some sachs clutch modifications

Ctrl+D On this one!

Re: Some sachs clutch modifications

What did you do to mill the pads?

Re: Some sachs clutch modifications

The 2 speed manual is very similar, someone a while ago put up a comparison, but no you can't make the automatic into a manual. but you could do the reverse.

The cases are exactly the same except they have different holes cutout, like for the shifter on the manual there's a hole in the top. the spot is there for it on the auto cases, but it's not drilled out, likewise the hole for the starter cable on the automatics is there on the manuals, but not drilled out.

Since the manuals sit at rest in 2nd gear, you could swap in an automatic donut spring, remove the pins, adjust the clutch lever so it presses everything together (instead of apart) and run it as an automatic. but that's worthless.

The automatics have no means of shifting, but if you got the 2 speed gear shifter and clutch parts, they'll fit into an automatic case if you drill and fill the proper holes.(edited)

Re: Some sachs clutch modifications

I milled them on a bench disk sander and checked regularly with a micrometer that it was very even. i left +/-0.05mm tolerances, it's not hard, somewhat tedious. the thicknesses arent even between the different pads, some i had to go a little farther to be sure they were very flat, but the thickness of each pad is within .1mm all around

Re: Some sachs clutch modifications

The clutch parts that are common between the manuals and automatics (nuts, spacers, pads, plates and bell) are totally interchangeable. If you had a 3pad/4plate clutch (some bikes did, treats had some up a little while back also) you could swap that into either setup, youd just have the springs pushing them apart for the automatic or the pins to push them apart on the manual.

I got the extra clutch parts from a second spare engine, so i took the thin plate and one pad from the 2nd clutch and milled all the pads down and assembled them as shown. Sometimes you can get new pads & plates from 77 also outta the old handybikes supply

I'll get a pic of the setscrew up soon

Re: Some sachs clutch modifications

will, this is a really good post! i'm working on some new parts for these, gotta get a few projects out of the way first.

its good to know your experience with the german uber clutch was so positive, i wasn't sure if it was good enough or still needed some work.

i've got a hook up on a replacement spring that hopefully will hold more power with the manual. I dont knwo if anyone has experimented with those, but i haven't yet and it seems to me like a logical next step. Did the uber clutch come with a stronger spring?

its good to know that that front spacer gets ditched, too, i couldn't ever figure that part out on my own, only could get 4 plates and 3 discs on mine.

Re: Some sachs clutch modifications

So these German 2speeds. How much would it cost to procure one? Would my friend in Stockholm be able to buy it for me? Links?

Re: Some sachs clutch modifications


Re: Some sachs clutch modifications

yea i do have the superspring too, theoretically spring is about 15% stronger which should make a pretty big difference, and even more difference since you're multiplying that across all the extra pad and plate contacts. I think i've got it so it's pressing harder against it at rest as well.


and here's just a side by side of the OG clutchpack and the much beefier uberclutch. the clearance issues become much more obvious.

Re: Some sachs clutch modifications

Oh and for some clarification on the automatic:

The numbering is a little different from the first diagram (and my first description) so pardon any confusion but i think you ought to be able to figure it out

What I did to keep the nut from coming off is to lock piece 18 to the crank (on any other clutch the equivalent piece would be taper fit to the crank)

here's a shitty photo but maybe i can explain it, sorry it was dark and my camera sucks

what you're looking at is the top of my clutch case. There's a hole drilled through it and i'm holding a flashlight on the inside so you can see in there.

the clutch pads have been removed so what you see in there is the toothed drive piece #18 through the left side of the hole and the donut #20 on the right. What you should be able to see is that I drilled and tapped a small allen head set screw in between the grooves. when it's all in place I can tighten (OR REMOVE!) the set screw and lock it to the crank. It's small enough that screwed in it doesnt obstruct the pads going on. The cap gets glued on afterwards to hold the oil in.

And some other good threads for reference,1983164,1983164,1796493,1796493,1777073,1777073


Re: Some sachs clutch modifications

Re: Some sachs clutch modifications

† CH∆D † /

Your my hero. Hook up the alsil?

Re: Some sachs clutch modifications

yeah on most motorcycles, people just upgrade the clutch springs as a band-aid to getting the clutch to hold better. i've found a totally different style of spring than the wierd toothed washer thing, and i'm going to see if the company that makes them can do a custom one for me, and what quantities i'll need to order.

I can easily make thinner steel plates, which is half the battle, but i'm working with my clutch lining guys on getting the thin fiber plates made. The smallest stuff they work with is 1/8" because they mostly do semi truck stuff, so it has been a challenge. I could make them out of 1/8 then cut them down with a grinder or something, but thats a lot of dicking around.

Re: Some sachs clutch modifications

nice graham, but yep, that's a lot of dicking around.

Once I made up some CAD drawings for the fiber pads. I was looking at havin some thin metal "pads" machined and then having some clutch lining applied on either side. Best I could source though it would cost like 40-50 bucks per piece. 150 net cost is not gonna give a feasible clutch replacement, and initial investment would be close to a grand.

I also tried to find possibly some stiffer round springs that might fit the manual, but i don't know how well they'd work in there. If you changed the dimension of the spring that'd also be a way to let more room for more pads/plates...

I'm also pretty pumped about the trac/a35 mount setup you got goin, I've got a trac and an a35 waiting to be mated, but it's a wayy low priority project.

tha alsil's a pretty solid pipe on this setup, way more durable than the hurricane blaster i'd been running. The nice thin about the alsil is it fits right on the flange mounts already. I drilled holes in the bottom of the outer fins on my jug to hook the springs onto, which works really well. mounting it to the cylinder means no more crappy clamp mount dropping off every 100 miles.

rugged spring mounted exhaust. score. have had no issue at all with it. it's def less power than the blaster though, but it doesnt break in half.


Re: Some sachs clutch modifications

yeah, great minds, eh dood...

my first thought was steel with friction junk applied, but getting it that thin would just be crazy... i'll see what i come up with.

the other option, what some drag harley dudes use, would be solid copper or brass sheets. Apparently it works pretty well against steel, but i just cant get my frickin' brain around it. A lot of chain saws run steel on steel but i just dont think that would be very nice either.

i have a stupid long list of problems/projects right now that need to be addressed before i can sink more time into my sachs pit. (its a pitbike.. get it! ha haaaa) I've probably spent more time on this bike than any other moped and i've only had it running once. at which point it blasted to 60 mph then promptly slipped the timing and i got mad and threw it in the back of the garage.

Mine has a puegeot 103 simonini circuit pipe on it that i really like, but it has broken in about 70 pieces (back when i was running 1 speed) and is now made out of more mig wire than it is the original pipe.

ARGHHHHH... sachs. what'ya gonna do.

Re: Some sachs clutch modifications

great stuff dude, been waiting on this; well worth it.

Re: Some sachs clutch modifications

just put an e50 on it...

Re: Some sachs clutch modifications

oh and whats with the all fiber old school plates in your "uber" clutch pack? my bike shattered those within 3 miles, the metal/fiber plates are the tops.

Re: Some sachs clutch modifications

can't wait to see this in action next week!

Re: Some sachs clutch modifications

FUCK. well i broke one of the pads. one of the uber pads. I'll probably put a milled down one in there, but yea, got about 1000 mi on it before it bit the dust. It actually just cracked the pad and still ran fine, I didnt notice until i toredown the engine to rebuild it with a D crank and mill out the cases for a 13t front sprocket.

on the other note; the milled clutch automatic setup was working great for about a month with the 80cc on stock gearing then that bike got disassembled for some cosmetic enhancements. but seems to be holding up alot better than stock 2pad. Whenever that gets back together we'll see how long they last.

Re: Some sachs clutch modifications

This needs to be in the wiki.

Re: Some sachs clutch modifications

Yea I wanted to let it flush out here but i'll wiki it.

Re: Some sachs clutch modifications

nerdzilla No mo Peds no mo /

hells yes. Me and will had been talkin about the manuals a bit lately.... Wanna send me a set of long pins? Graham. Make us some plates! Then I don't gotta spend hellA dough!

Re: Some sachs clutch modifications

Raphael Davis /

well done!

Re: Some sachs clutch modifications

WELL! 2 months and one of the ground down pads broke itself. bummer, guess they are hopeless, unless you get some metal pads and clutch-liner them.

Re: Some sachs clutch modifications

will whats the scoop on the heavier gauge clutch spring-plate? is it awesome?

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