Sachs Clutch Issues and Slip

So ive posted a few times about this bike im buiding, but would like to narrow the issue down to the specifics. Sachs 505/1d engine. When i run the bike, I get up to about 5mph and it hits a wall. Like ive lost the clutch-just spins or something-no power to rear wheel. What may cause this to happen at higher RPMs? Im playing around with different shim sizes, but nothing seems to be helping. Ive tried a couple different springs too - one very tight and the other a tad looser. Im trying to understand what causes this mechanically but cant wrap my head around it. ive taken this clutch apart about 100 times now... just hoping someone can identify this issue specifically.

Re: Sachs Clutch Issues and Slip

♣Slew Foot♣ /

You need to shim it better. Use the fat wave washers thin plates and be sure that it engages when the launch is pulled the pivot point screw just tells the bell how much compression is used to engage the cup loosen it a bit add shim washers after the last plate. The clutchnuts loosen. There is no washer before the bell

Re: Sachs Clutch Issues and Slip

Ok perfect, im gonna try all of that. thank you dude! just to be clear, the washer you're referring to is number 13 on this schematic right? (edited)

sachsclutchweb.jpg

Re: Sachs Clutch Issues and Slip

Make sure everything spins free on the stand - cover off, and turn the rear wheel. If not, something it too tight.

It's the #200 weights on that round spring that fling out and engage everything when you rev the motor.

I've found that the clearances don't matter so much. It just needs to engange when you rev it, and disengage when you stop. That engager needs to feel some play at rest.

Re: Sachs Clutch Issues and Slip

♣Slew Foot♣ /

# 22 is wrong on some.

The. 14s hardware store bring one with for the id of the hole

Re: Sachs Clutch Issues and Slip

So i think i've tried everything at this point... still no luck. The shimming doesnt seem to make much difference... same result. Get up to about 5mph and its like the clutch cant keep up with the RPMs and this slowing starts to happen, the "wall". A moment after that, if i try and push through it, I lose the clutch nut. I even tried putting two nuts on there and it still somehow came loose. I will try the loctite method next, but really didnt want to do that until I resolved the initial issue. Feel like im gonna put that loctite on and its just going to fail again and then ill have to deal with the nut being stuck when trying to disassemble again.

Im running it now with all thin plates and switched the washer for something thinner so i could fit a second nut on. but I also tried without washer, with original washer, with original plates, no shim to 3 shims, scored all plates and disks, all sorts of bell adjustments, tried two different springs, same result. This bike is kitted... so the rpms are high...tops out really quick... maybe if i adjust timing to hit more lows more gradually? I dont even know how thatll work out. I have seen plenty of kitted sachs and they almost all have the same damn clutch setup. most not even modded at all. just stock. what am i doing wrong here ... ugh.

Re: Sachs Clutch Issues and Slip

If your nut is coming loose, it's not torqued to spec. I would deglaze the the clutch lining and reassemble as per the manual, torque with Loctite. No problems with my kitted 504.

Re: Sachs Clutch Issues and Slip

I set it up stock, and loctited the nut. it's staying on there. but now i am dealing with the original problem i had before i rebuilt the bike. After running for a minute, it sound like the piston is smacking around in the cylinder or something. terrible sound. I posted a video back then and no one could identify it, so i decided to take the entire bike apart and take a look. I didnt find anything. Engine looks great. It's like something is making the bike reject the clutch. sounds like when its set up on there properly and nut is tight, the engine is trying to run backwards or is jerking- or something. I really have no idea and cant really explain it. The only thing that doesnt look/work right on this thing is the rear wheel. It has tight spots with the chain. It's the only issue that i cant seem to resolve. But those tight spots - I can push through them easily. This bike has to push a 160lb man down the road, if it cant push through some tight spots that are barely noticeable, then idk. I just cant see that being the problem. But seriously, I just put like $600-700 into this bike and its gonna now sit and rot cus im at my wits end with it. zero ideas and im exhausted by it.

Re: Sachs Clutch Issues and Slip

Is it the rear wheel or engine? Disconnect your chain and spin your rear wheel. If your wheel spins correctly, you need to disassemble your engine again and see what's wrong. Take a break, then just do it.

Re: Sachs Clutch Issues and Slip

Here is a photo of two clutch hubs, one came with the bike originally and the other is the replacement i found. notice how it looks like the old hub has been ground down by the plates? What would cause that - and maybe thats the sound im hearing? Also, a photo of the engine before i sealed it back up... Let me know if anything looks off.... Just trying to get any ideas going here.

tempImageQKQHKP.jpg
tempImageG0pIh4.jpg
tempImageCBzViR.jpg

Re: Sachs Clutch Issues and Slip

Oh also, whatever is causing this, just completely destroyed my flywheel. I think this bike is toast

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IMG_5064.JPG

Re: Sachs Clutch Issues and Slip

This is the sound. you can hear it in the middle of the video and very end.

(edited)

Re: Sachs Clutch Issues and Slip

That crank is salvageable with valve grinding compound and some elbow grease. Bad luck though for aure

Re: Sachs Clutch Issues and Slip

That clutch drive is definitely a problem. As wormdirt said, valve lapping compound "may" make that crank serviceable without the key.

If I had to guess, your problems on both ends of the crankshaft were due to loose nuts. Did you torque them to spec or just guess?

Re: Sachs Clutch Issues and Slip

Yeah i believe i hit the mark on torque. Im sure they have been loose though while i was messing with the clutch - taking it apart again and again. maybe trying to run it again and again after so many corrections made it fail. which brings me to an update on the sound....

The sound was the flywheel and crank just rattling around together given that groove kept getting bigger and bigger on the crank. I actually just put the flywheel back on and torqued it down without the little bit in there just to see and now the bike sounds perfect. Doesnt help with the main issue though. Still get up to like 5-10mph and the RPMs keep going up and up but the rest of the bike doesnt respond. almost like the clutch stops performing at all. And its not glazed cus i was just in there with sandpaper roughing everything up... I just cant understand this.

Re: Sachs Clutch Issues and Slip

Get another crank, flywheel, key and a complete clutch from a known good setup. Or maybe just sell it and cut your losses. It looks like you are out of your element. Best of luck.

Re: Sachs Clutch Issues and Slip

♣Slew Foot♣ /

True the crank its wobbly.

A cigarette paper and redlocktite + heat gun = no slip on nuts. Or stators w/o keys.

Re: Sachs Clutch Issues and Slip

. (edited)

Re: Sachs Clutch Issues and Slip

♣Slew Foot♣ /

A reasonable machinist can true it take your woodruff out first. Bring just the crank. A local old guy is key. He will get a kick out of it. 20 bucks.

Re: Sachs Clutch Issues and Slip

OK, the wallowed out clutch spline is a thing that happens and almost certainly your probelm. it happens if the shimming is wrong or the spring washers not tight the clutch pieces seem to be able to tilt a little rather than slide in and out smoothly and they wallow out a groove, but once it starts getting bad they will get stuck in the groove and that prevents them from being adequately compressed together and engaging, and so it slips. Usually you notice this either being super hard to get it to engage with the starter clutch, or conversely from a stop the engine will rev high and then clunk into engagement as it overcomes the groove, sounds like yours is never getting past that groove and looking at it, it's easy to see why. that thing is thrashed. It's fairly common, but never that bad. usually you can file them with small file and get it to slide smoothly. Also check that nothing is crooked or warped the plates, and that the clutch donut doesnt have any stuck together segments or twisted sections or anything. replace with the good spline piece, and you should be OK at least for a while.

Regarding the flywheel keyway, unfortunately that's also common, but it's not directly related. I think that winds up happening because people love to skid stop the coaster brakes, which immediately locks up the rear while the engine is still engaged and trying to spin and it clunks the flywheel like an impact. it's alotta imact, and maybe that also contributed to your clutch problem but i dont think they're causing one another, just maybe symptoms of the same abuse.

Anyway, you don't need that key. You can absolutely get away with grinding down any raised sections, removing the wrecked key entirely, and using the valve lapping method to clean up the taper. as you do it, check to make sure it's all getting shined equally - no high spots. once it looks even, set the timing where the key would have been, and tighten it on. the press fit onto the taper will hold it exactly where you put it. Lapping may require you taking the crank out tho, and at that point might as well replace the whole crank, you can probably find a good one on here or get a fancy one somewhere. Dos cycles has some A cranks, if not on their site just email them.

I've run several sachs and other peds with a lapped crank and just press fit onto the taper at the right timing. it's totally fine, all the woodruf key is really for is lining up the timing.

Anyway that should get you where you need to be. good luck

Re: Sachs Clutch Issues and Slip

Thank you soooo much for the thorough response. So appreciate that! So yeah that thrashed spindle was the one that came with the bike. I replaced it before trying to start the bike originally, but assume im dealing with the same issues the last owner had with this thing... So im definitely listening on these pointers- dont want it to happen again. I think maybe the one thing i really havent tried is the heavier duty spring washers- I cant seem to find any at hardware stores that arent super industrial strength. If i do find some that seem doable, ill definitely try that first.

The shimming is throwing me because i've set it up text book, and also have tried going thicker and thinner - So i just dont think the problem is there. But ill keep fiddling with it.

The spring looks really good to me. I have the original and it was totally beat, so i replaced it with one off a spare 404 I had (are all stock Sachs clutch springs the same?)...Maybe i could replace it with a tighter spring... since its kitted, i feel like its "engaging well below where the engine is making power".

Thank you for the flywheel advice! Im doing just that for sure. Should work out alright.

Re: Sachs Clutch Issues and Slip

> Born to be WillD Wrote:

> -------------------------------------------------------

> OK, the wallowed out clutch spline is a thing that happens and almost

> certainly your probelm. it happens if the shimming is wrong or the

> spring washers not tight the clutch pieces seem to be able to tilt a

> little rather than slide in and out smoothly and they wallow out a

> groove, but once it starts getting bad they will get stuck in the groove

> and that prevents them from being adequately compressed together and

> engaging, and so it slips. Usually you notice this either being super

> hard to get it to engage with the starter clutch, or conversely from a

> stop the engine will rev high and then clunk into engagement as it

> overcomes the groove, sounds like yours is never getting past that

> groove and looking at it, it's easy to see why. that thing is thrashed.

> It's fairly common, but never that bad. usually you can file them with

> small file and get it to slide smoothly. Also check that nothing is

> crooked or warped the plates, and that the clutch donut doesnt have any

> stuck together segments or twisted sections or anything. replace with

> the good spline piece, and you should be OK at least for a while.

>

> Regarding the flywheel keyway, unfortunately that's also common, but

> it's not directly related. I think that winds up happening because

> people love to skid stop the coaster brakes, which immediately locks up

> the rear while the engine is still engaged and trying to spin and it

> clunks the flywheel like an impact. it's alotta imact, and maybe that

> also contributed to your clutch problem but i dont think they're causing

> one another, just maybe symptoms of the same abuse.

>

> Anyway, you don't need that key. You can absolutely get away with

> grinding down any raised sections, removing the wrecked key entirely,

> and using the valve lapping method to clean up the taper. as you do it,

> check to make sure it's all getting shined equally - no high spots. once

> it looks even, set the timing where the key would have been, and tighten

> it on. the press fit onto the taper will hold it exactly where you put

> it. Lapping may require you taking the crank out tho, and at that point

> might as well replace the whole crank, you can probably find a good one

> on here or get a fancy one somewhere. Dos cycles has some A cranks, if

> not on their site just email them.

>

> I've run several sachs and other peds with a lapped crank and just press

> fit onto the taper at the right timing. it's totally fine, all the

> woodruf key is really for is lining up the timing.

>

> Anyway that should get you where you need to be. good luck

The reluctant Sachs Guru speaks, and it is so.

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