Sachs 504 flywheel ran off last night

And took a big chunk of the crankshaft with it.

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It probably flew 100 feet into the woods.

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My camera is awful so the second photo was from the front-facing.

I’m thinking maybe it became loose and yanked the woodruff key, cracking off a perhaps already cracked or weakened crankshaft end... it looks to me like shearing though. I’m very mystified about it but either way, I’ll need to find a new bottom end or a 504 crankshaft. I have a wtb thread in buy/sell/.

Bike is a Sachs Westlake

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Re: Sachs 504 flywheel ran off last night

How many RPMs did you hit and how many birds did it kill?

Re: Sachs 504 flywheel ran off last night

Tri-ped Dave O.D.B. /

At least the 504 is one of the simplest to split and replace the crank. Try and find a D crank with the longer stroke so at least you gain some power fr your efforts

Re: Sachs 504 flywheel ran off last night

fuck her. just let her go, man

i known it hurts but there's plenty of other flywheels out there

Re: Sachs 504 flywheel ran off last night

♣Slew Foot♣ /

So tell me how the fuck does that happen I mean there's not supposed to be any Shear forces on that flywheel did you have a hard Seas?

Did you have a cover on it maybe something Jam the flywheel that is really a mystery I mean the clutch side I can see shearing if it jammed but something had to go horribly wrong for that to just fly off I would be looking for a deeper cause maybe an intermittent bearing seized

Re: Sachs 504 flywheel ran off last night

if it wasnt flush to begin with could it theoretically wobble off?

I cant picture how it happened either?

Re: Sachs 504 flywheel ran off last night

Sean Colvin /

Done some more thinking - Was noticing that when you go hard on that thing from a standstill lately the clutch would grab really violently, like the shimming was off (it’s a Sachs thing). I’m thinking that my friend, the one who owns the moped, was coasting at the end of a straightaway near my house and pinned it as he turned to go up the hill. The clutch probably grabbed really violently and jerked the crankshaft in a way that caused the flywheel to shear off.

As for the intermittent bearing seize - that’s funny that you mention that because we were also experiencing a strange problem a few weeks ago that we believed to be clutch-related, when the crankshaft would just get stuck in place when we were trying to kick start it. When you use a ratchet to turn the flywheel it would loosen right up as if it was merely the high compression of those jugs - but who knows, could have been a bearing starting to stick. The bottom end never sounded crunchy or loose or anything. Thanks for the responses.

Re: Sachs 504 flywheel ran off last night

Crank is super wimpy on these. I can see why this would happen. It won't be so easy to drop in a d crank, the ignition side tapers are different and the 504 cases take the smaller bosch points ignition.

Re: Sachs 504 flywheel ran off last night

♣Slew Foot♣ /

Bingo lower Conrod bushing failure

Re: Sachs 504 flywheel ran off last night

♣Slew Foot♣ /

And just so you know I have a 505d crank but it has a mocked-up keyway for the stator and it was spray welded on the crank side so it already happened...

Re: Sachs 504 flywheel ran off last night

Before we go thinking you can put a 505 crank in a 504, you cannot. the aftermarket sachs cranks don't fit a 504. there is no "D" crank for a 504: Read this one: https://www.mopedarmy.com/forums/read.php?1,4257783

If you wanna get clever you can put a 505 crank in a 504 but you need to run a late model smaller tomos flywheel or a puch sized HPI and also make your own stator mounts and spacers and then set timing without the key. You also have to grind down the old 504 stator mounts because theres a lip so you can't just bolt on a different stator. not cheap or easy, but doable

Theres a wiki on "Sachs motor differences" with a lot of other good general details.

also, that's definitely fatigue failure - the flywheel probably got loose and with the start&stop, and hard engagement, it was wallowing out the keyway, allowing it to twist farther forward and back until you get a crack growing, then the flywheel gets enough offcenter and every single rotation at like 5000 a minute, is a little tiny flex, like bending a paperclip over and over and over til it cracks. shitty.

I don't have any, I looked yesterday and only got one 504 that I do still need.

Re: Sachs 504 flywheel ran off last night

Didn't we decide that the kreidler flywheel is 505 taper and uses the small Bosch ignition?

Re: Sachs 504 flywheel ran off last night

derek cuellar /

time to go flywheel fishing in the woods.

Re: Sachs 504 flywheel ran off last night

oh yea!, I forgot about that one - did we ever check? I don't have that flory anymore.

I think the flywheel didn't fit but the kriedler stator did.

So we can get a flory stator, derbi motoplat flywheel and a D crank and we've got the 505 crank in the 504 easy peasy. game on fuckers lets make this happen.

Re: Sachs 504 flywheel ran off last night

Could always cut the taper of a v1 flywheel too, v1 also take the 90mm stator plate

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