Sachs 505 Clutch Issues

Hello everyone,

My 1980 Sachs Suburban with a 505 1/d, unfortunately, still hasn't seen much riding. I have now had the clutch apart at least a dozen times with varying results. The bike is completely stock and it great condition with around 800 miles on it. Here is everything that I was able to find out:

With the stock 1.2mm shim in, there is no axial play and the clutch is always fully engaged. With this, I was easily able to get the bike up to just under 30mph, but of course, it would die at stops.

With three 0.2mm shims in, there is optimal axial play (between 0.4mm and 0.6mm) and I can get the bike to idle at stops, but it seems as though the clutch never fully engages because, at full throttle, the bike only gets up to around 15mph. When the bike is idling on the stand, the rear wheel is always spinning, I can stop it with the brake and the bike will still idle, but when I let off the brake, the rear wheel starts spinning again.

I then decided to try and see if I could get the bike to idle on the stand without the rear wheel spinning so I took out all of the shims and ran it like that, but this had the same results. The rear wheel would continue to spin when I let off the brake. The bike's idle sounds fine so I don't think that it's just idling too high and I can't get the idle any lower without it dying.

I also tried out running four and five 0.2mm shims and had the same results as three, except the bike was harder to pedal with the engine disengaged, as expected. I would have also expected to be able to go faster than 15mph with more shims, but no dice there somehow.

I was having issues with the center gear hub and the plates hanging up on certain spots of it, but I was able to remedy that by sanding those spots down. All plates move freely along the gear. The two fiber plates appear to be in great condition, one is 3.5mm thick and the other is 3.4mm. I've scuffed them up with 200 grit sandpaper multiple times. I am completely clueless as to what might be causing my issues. I am considering buying 0.1mm shims and/or the aftermarket clutch plates sold by lucky2 strokes and playing around with those, but it is entirely possible that my problem is somewhere else and I would just be wasting money.

Any suggestions would be greatly appreciated. Hopefully, with some help here, I can finally this thing out on the road as the clutch is the only thing holding me back. Thank you.


Re: Sachs 505 Clutch Issues

♣Slew Foot♣ /

You can mix and match the plates so it just fits the main thing is that Central COG if that's all good and Lube the place should slide freely and pop in and out the rest is just about pressure that little screw thingy on the launch whatever

Re: Sachs 505 Clutch Issues

If you go back to the too tight setup does it go back to going 30? I mean are you sure the 15mph limitation is clutch? If the clutch was spinning too much you'd hear it continue to rev up but without going any faster.

One check, and only do this to check, is pull the starter while riding. that will force the clutches to engage. You don't want to do this for a long time but if it makes your bike get up over 15mph then agreed, you've determined it is a clutch engagement issue. If no change though, I think you'll need to look elsewhere, timing, decomp, jetting, carb problems, plug or points etc

as far as the rear wheel spinning, the clutches always have some resistance wih the oil and whatever. as long as it idles without having to be a high idle, and as long as it's not tugging you along at a stop, you are OK. Also, be sure you've got the wavy spring washers with each pad. you may be able to anneal those just hitting them with a torch or may benefit from replacing those to help push everything apart better and disengage at idle. But I don't think that'll be necessary.

Re: Sachs 505 Clutch Issues

Ok, so I found some time today to mess around with it a bit more and you were right, I went back to the stock setup and sure enough, I could only get up to around 15. I know for a fact when I tried that last, which was likely a couple of months ago, I was able to get to 30. I haven't done anything with the bike since then so I'm not sure what has caused this. Also when I was riding it today, I could hear it wasn't running right. I think I might pull the flywheel and clean it up a bit, it being rusty was the reason this bike wasn't running when I got it. I also might throw in a new plug and gas, the current plug looks like its fouled from running rich and the gas is about a year old. I'm not sure how to go about getting these mopeds to run leaner. Would I just need to find a smaller jet? I have the stock square bing and the stock airbox as well. I also might as well clean the carb up again.

I'm also curious as to how the bike can have zero axial play in the clutch, but still need the starter lever to start, does that make sense? I figure that zero axial play means that the clutch is engaged, but that doesn't seem to be the case.

Thank you for all the input, I'm finally making some progress to getting this thing out there in the nice weather.

Re: Sachs 505 Clutch Issues

if u wanna run leaner, run half the airbox and some panty hose wrapped on the end

Re: Sachs 505 Clutch Issues

there's a small amount of axial play but it's held in place by the spring washers. you can't really detect it pressing or poking by hand but with the bike running and lube warmed up between the pads and plates and the significant leverage of a stopped wheel holding things in the back half you get a smooth steady slipping at idle (ideally)

you can't see it really but I bet if you tried pulling the starter lever while watching you'd see the little additional compression to where it's fully engaged during starting vs the expected axial play you're not seeing just staring at it.

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