Sachs 504: Faster than 20mph?

I just got my first moped, a 1975 Hercules P1 with a Sachs 504/1BS. It's got a 85/10/101 Sachs Bing carb, and true to the sticker on the side, tops out at 20mph.

Is there anything I can do to improve performance that's relatively simple? (doesn't require boring or welding). I've been reading as much as possible over the last few weeks and it's looking like the Sachs, while reliable, are maddening to performance tune.

I thought I'd start with a better air filter and a larger jet, but the square bing carb jets look impossible to find. Would a 12mm carb help me out? Or is the intake so small that it wouldn't do any good? Would a different exhaust make a difference?

I'd be happy with even the smallest improvements. I just don't know where to start. I'd love to hear from anyone else with a Sachs 504.



Re: Sachs 504: Faster than 20mph?

Ok 504's are kinda not exaclty know for thier power in the first place, but they are cool motors and they are reliable as a brick stock.

the problem is , have a b model which is the intentionally restricted 504 so its slow as shit.

they do this by using a exhuast that is restricive ( see how it bottlenecks once it leaves the engine?) , using a 10mm carb instead of the 12mm the A model uses, and actully just to make your day worse the porting in the exhuast port is different, (smaller ) and the clutch is a bit wimpier ( and they aint nothing to write home about in the first place.

Id look around for a 504 /a and get a decent stock pipe that isnt restricted and you will be a much happier camper with a 32mph bike.

get any thoughts of using a 505/d out of your mind , thats another discussion alltogether, it will not bolt up and it aint worth it anywho.

I actually have a 504/a with ultra low milage , email me if your interested.

If your looking for the ultimate in cheap, you could go for a decent unrestrictive header pipe and a delorto 14:12 and jam it on the manifold you have but you will always be fighting the internal inside the barrell resrictions of the b barell, and while not insurmountable, tis way harder with that damned sachs all one piece head...

Re: Sachs 504: Faster than 20mph?

Step 1: Remove 504 engine

Step 2: Bolt in stock Puch engine.

Step 3: make bracket to mount exhuast on left side.


Re: Sachs 504: Faster than 20mph?

Rob @t ATTN! Burrito /

do this:

bigger carb. 12mm will get you to 25 mph alone, a round bing will work if you want to grind the bottom nut off- then you can get a 15 bing and 15mm intake- but then you have to use a small strap wrench to open up the bowl. a sha intake is available but it's 40$. usually the slides and needles are different going from the 10 -12mm if you keep with the square bing

better exhaust header. i used a puch one that most people make the 24mm intakes out of- but that's just because i had it laying around. alot better torque, mines held on with springs. not quite the best seal.

sprockets. you probably have a 9-10 tooth front, get an 11, and on the rear take it from what is most liekly a 50 down to a 46 or so, and you'll get up to 30ish (with 12mm carb).

head gasket. not sure on this one, but have heard some restricted ones have a thicker or multiple head gaskets to lower compression. mine didn't.

Re: Sachs 504: Faster than 20mph?

Rob Sachs doent use head gaskets cause they are all one piece barrells, A better exhaust is a little helpful but not much because they actually have made the exhaust port on the 504/b smaller. So the actual exit that the pipe clamps on to is actually physically smaller then a 504/a . They made it difficult. the 12mm carb would be the biggest help but your always gonna be fighting with a 504/b performance wise.

Bret - there was some rumors out there that a puch e50 or za would mount right up to the sachs frame. Its simply not true. they arent even close. Or most of us sachs powered bike owners would have za50's or e50's . You could do this easily enough with a welder and fabrication of mounts but its definately not plug and play ( it did day this on the wiki once that you could swap them but they took it down)

Your best performance enhancement would be a 504/a, or if you really want to go fast, doing like bret said and doing a motor swap. I recon if you cut the frame section off an old maxi with a rusty frame or something you could weld em into a sachs mount frame

I know my sparta's would all give thier eye teeth for a za50 with a polini.

Re: Sachs 504: Faster than 20mph?

Rob @t ATTN! Burrito /

crap yeah i meant base gasket- any truth to that?

Re: Sachs 504: Faster than 20mph?

i tried the double base gasket but it didnt seem to do anythng. My sachs was still and still is a 32 mph bike.

I also think the clutches in them can take just about what the motors can put out. The fact that the 504/b has a smaller clutch then the infamous chatter box in my a's scares the hell out of me. Maybe he can find a 504 a jug and 12mm carb?

Its just that whole 504/ a's are so cheap....

Re: Sachs 504: Faster than 20mph?

Mike McScoutington /

I had the same slow ass Sachs as you Ryan. I swapped to a 508 case (ported like a 505 with the longer stroke and all but does not have the pedal shaft through the case), d cylinder, 12 mm square Bing, sorry can't remember the number, and a fat header. I regeared, but again can not remember the ratio, and now that bike will do about 35 or 36. It takes a second to get into it, but when it does it moves alright.

Re: Sachs 504: Faster than 20mph?

See, now puch engines are much easier to get than a sachs 508. This is what i'm talking about. If you even consider changing engines, go puch. Bolts right in!

Re: Sachs 504: Faster than 20mph?

Jesus i hate disagreeing with people with little pictures next to thier names, especaially ones with the little creatures things, but dude, your wrong, Creature or not. A puch motor will NOT bolt up to a sachs frams.

Take my word for it, there is an e50 sitting right on my bench next to a sachs powered sparta frame. The sachs frames use 2 bolts to hold a heavily rubber mounted / dampened skinny ass cased 504 in the frame. An e50 is to Fat. WAY to fat. Needs all new motor mounts. So it is as easy to say a batavus motor fits in there or a tomos motor or a kawasaki kx100 motor. Any of those ways, and your welding in mounts and alighning the chain and stuff.

It wont bolt up.

Re: Sachs 504: Faster than 20mph?

However , id weld up a puch motor before i ended up deeper into sachville land swapping out cases, ( and cranks when it comes to the 49cc crank that comes with the d motor, totally different stroks ) any day.

Re: Sachs 504: Faster than 20mph?

Well, looks like there really is no cut and dry answer...just what I was afraid of. Finding a 504 /a or another ped altogether might be the best long-term options.

I might start out trying the 12mm bing and better exhaust header. Sprockets might also be an option. Thanks all for your suggestions. If anyone else has had luck with the slow 504/B I'd love to hear it.

Re: Sachs 504: Faster than 20mph?

Mike McScoutington /

You know, I hear that 20 is the new 40, so you should be solid

Re: Sachs 504: Faster than 20mph?

if you re sproket it is gonna be SO damned slow off the line your gonna need one of those things they use to get planes off the deck of aircraft carriers man.

The b is so slow its miserable. The 12mm and the exhaust will help to some extent definatley.

Re: Sachs 504: Faster than 20mph?

Hmmm, i was talking to someone about a ktm foxi and a puch engine and i was under the impression that it would work. I'll have to talk to Elliot about it.

Re: Sachs 504: Faster than 20mph?


Thanks for the tip. I'll start there.

Re: Sachs 504: Faster than 20mph?

i think i actually have an exhuast header somewhere ill look around. I know i have a 12mm square bing...

you could always run those and keep an eye out for a 504/a cylinder or maybe put a wanted onthe buy sell

I think that there was a ktm foxi and a ktm that actually did take a puch motor which may be what is confusing you bret, but the sachs motor mounts are way different.

Re: Sachs 504: Faster than 20mph?

Handy bikes has exhausts on ebay. They mount on the right side i believe so if you have back pedal brakes you are sort of SOL

Re: Sachs 504: Faster than 20mph?

Yeah, you can make a puch engine work.

and a 504 and a 508 are the same thing. you can swap a square head, bigger carb and bigger pipe on it, and it'll go faster.

Re: Sachs 504: Faster than 20mph?

Mike McScoutington /

504 and 508 are almost the same. The porting and cylinder studs are different. A D cylinder would not mount to the old 504 I had unless I would have drilled and tapped new cylinder bolts and ported like crazy

Re: Sachs 504: Faster than 20mph?

God this piont makes me nutty.

I think cause i tried to do this based on info from the wiki that said it was a bolt up. I had a sparta frame in my living room right next to an e50 as a pic perfect proof that it wont just bolt on there.

If it did, why in the WORLD would anybody be blowing clutches out of the side of thier sachs motors trying to make them go fast? Sachs are a pain in the ass ( and I LIKE THEM ) There isnt a big heavy sparta or foxi that wouldnt give its eye teeth for a nice ol metra kitted e50 or a magnum za. Id have 7 504's on ebay in a day if they bolted up.

Ill pay for a picture of an e50 BOLTED into a frame that a sachs came out of. I dont know where the myth of the e50 will bolt up came from, but its not true and it wont work.

Of course you can hack and weld one in there, but you could do that with almost any motor. Whats the point? The guy specifically said he didnt wanna do boring or welding, and an e50 isnt going on a sachs framed bike without welding a motor mount in there.

Re: Sachs 504: Faster than 20mph?

I forget if it's the A or B that has one stud in the wrong spot.

Re: Sachs 504: Faster than 20mph?

Honestly - there is a cut and dried answer on this - a puch motor will not bolt up, nor will a minerelli or a chevy 350

Im gonna get all man catty tonight and take a picture showing how far off the bolt mounts are and more importantly how the frame is to skinny for the back of the e50 or za case.....

Those handybikes exhasts are for the other bikes, they wont work on a balboa unfortunately.

Re: Sachs 504: Faster than 20mph?

@andrewhed: I might be interested in that square bing.

What would be a decent exhaust for a 504? It's on the left side of the bike, and I do have backpedal breaks...I'd prefer to not block the pedals if possible...

Re: Sachs 504: Faster than 20mph?

Ryan, if you have back pedal brakes, you have a 505. As for the exhaust being on the left side, that's what a lot of them are.

performance options - almost all of them require cutting and welding. Even the gianelli that is made for sachs, that clears the pedals will crack and need to be welded up after a year or two.

Andrew- the bolt-up easieness may also depend on which foxi frame used.


get a puch engine more often than


Hey Miker- do you have a picture of the bottom end you had problems bolting the square cylinder on, just for documentation's sake?

Re: Sachs 504: Faster than 20mph?

Ryan, if you have back pedal brakes, you have a 505

Hey, thats right lol!

All balboas are 505's

That makes things WAY easier in terms of making it get out of its own way.

you can find a 505/a which is better

the 505/c which is even better then that ( square boxy jug )

or , now that you know it will take a 505, a a 505/d would be awesome.

I had a balboa with a 505/c and it was pretty damn quick for a sachs ( way quicker then a 504 ) but it had the 12mm carb and a big exhuast header.

Re: Sachs 504: Faster than 20mph?

mike would be able to tell you if a regular 505/a cylinder would just go right on and have the case transfers match on the balboa 505, you might be able to just slam a decent jug on there and go ( im betting this is true )

Mike- im confused as to how a ktm foxi with the same skinny frame bit in the back could hold a puch motor any easier but ive not had a ktm foxi so am interested. I like those ktm versions, they are kinda hip. Like a sachs maxi lol.

Re: Sachs 504: Faster than 20mph?


I originally thought I had a 505 because the first 3 digits of the vin # were 505. Then, when I took the panels off to take a look at it, the engine clearly says Sachs 504/1BS. Also, the pedals don't go through the engine like they do in the 505. But I definitely can brake by backpedaling.

Re: Sachs 504: Faster than 20mph?

its a 504 then

if the pedals go through the case its a 505

it the pedals go through the frame like a puch , its a 504

there were some later ktm foxi's that used 505's but if you have 2 chains its a 504 !

Re: Sachs 504: Faster than 20mph?

Yup, two chains and extra slowness.

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