Watercooled 75cc Sachs 505 Project

So, in my wanderings through the murky depths of moped knowledge, I have made a discovery.

There is an ebay auction on ebay.de that lists a water-cooled cylinder kit as being adaptable to a Sachs 505 engine, as long as you "adapt the block."

I will post the translated text and images below:

This is an aluminum cylinder Nicasil Malossi sentence water-cooled, and about 47mm bore 75ccm. The cylinder is originally for the Aprilia af1 thought. You can also on 505 Hercules engines built when the bloc adapt. Also on Simson Motors can build the cylinder. I have a performance chart of the company long-tuning of this cylinder 17HP and over 120 km / h reached. The cylinder is just 10km running, and is as good as new. There are all the parts like pistons, cylinder, cylinder head, Malossi 4-fold and all diaphragm seals.

So, I just bought a 504, and I think I am going to scrounge up a stock AF1 cylinder and see just how close this is. If the bolt pattern and the stroke length match, I'm all in. I know that a 504 is not the optimal sachs to be using for this sort of mod, and I might look into grabbing a set of 505 cases and crank to compare. The kit uses a funny exhaust mount, so I think I would have to fab up a custom header and probably weld it onto a 6p or a Peugeot Doppler.

Anyway, I thought I would put this out there and see what y'all think.

Re: Watercooled 75cc Sachs 505 Project

🇮🇹💦 Of the Loin /

i have a 505. I can just take measurements for you i guess?

its a 505/d so the crank is different though.

Re: Watercooled 75cc Sachs 505 Project

I think I am just going to grab a 505 engine from somewhere. There is a cast iron Polini Kit that seems like it would work wonders.

Look at the teensy intake!

Re: Watercooled 75cc Sachs 505 Project

I am pretty sure thats the same kit the crazy euro dudes put on puchs. Polini af1 that is. Lots of work needed of course, but an e50 can take more of a bearing I would think.

Re: Watercooled 75cc Sachs 505 Project

All well but stk clutches are weak on larger cyls. Maybe you can fabricate a better clutch

Re: Watercooled 75cc Sachs 505 Project

I was actually thinking of replacing the entire transmission with a variator and pulley setup. No more gears!

Re: Watercooled 75cc Sachs 505 Project

fwhew.. for a second there Bret I'd thought youd forsaken the variator

Re: Watercooled 75cc Sachs 505 Project

No way man, keep safe the variator! Single speed autoclutch is the lamez.

Re: Watercooled 75cc Sachs 505 Project

Hmmm, so I just happen to have a 505 and 504 case sitting around, and know how to use a drill and a tap. the hard part would be deciding where to cut the sachs ..... if you replace the clutch with a variator, you would also eliminate the weak-ish sachs clutch. so would you go with a 2 pulley variator, or would you make it a one pulley swinging Belgian bastard?

If you can chuck the engine case up in a drill press, you could probably MAKE anything fit anything else, as long as the cylinder goes into the case far enough.

"130cc sachs":http://www.youtube.com/watch?v=rmpPFvlYrrg

Re: Watercooled 75cc Sachs 505 Project

(!) drool.

the spigot exhaust mounts on the sachs engines aren't so hard to deal with, naz just helped me with getting a 6p on my sachs 70cc reed valve athena 505. (i will be doing the same with a tomos estoril on an 80cc reedvalve athena soon also.) it didn't take much at all. an adapter between the spigot mount and the flange would work also.

Re: Watercooled 75cc Sachs 505 Project

Yes, this kit is used by some guys over here to adapt to an E-50. There's a lot of work in it tho.

The exhaustmounting would be the least of your problems mounting this kit up.

The stroke is the same. Both 42mm (You would need a normal engine, not the "long stroke" 505 engine), but your bolts will probably be far from lining up. That's the first thing you'd need to adapt.

Then you've got con-rod length. If the length of the conrod is not the same, you will need to raise or lower the cylinder to get the proper deckheight. You can do this by making a plate (if the con-rod is too long) which can also fix your bolt spacing and the utterly large transfers. Or you can remove material from the block or the cylinder if the con-rod is too short. A deckheight of +/- 1 or 2mm would be good, as you can then vary the deckheight by using multiple gaskets.

Then you've got the fact that it's watercooled. You'll need a waterpump that's either electric or belt-driven. You can buy the belt-driven waterpumps from www.mopshop.de. Get a radiator from a scooter or small motorcycle and you're good to go in the cooling section.

And yeah, you want to loose the stock clutch. It will never hold that kind of power. It can't even handle a badly tuned 80cc Athena :P I love the variator idea and would love to see how you work that out. I've been thinking about adapting a variator to an E-50, but I won't go into detail about that till I've actually tried it :P

Having said this all, I wish you the best of luck. Very wicked idea and if this works out well, you've got yourself one killer ped.

Re: Watercooled 75cc Sachs 505 Project

the sachs engine, in my opinion, has a few major flaws that would need to be addressed before it could handle a ton of power

1) the crankcase is both too-big and poorly shaped, giving it a poor primary compression ratio. the funny shaped crankshaft hurts even more.

2) the clutch attaches to the shaft without any sort of spline, key or anything. it is just held on by force, and the shoulder that holds it is really puny.

3) small gears

4) the 505 has a ton of extra drag in the drivetrain because of the extra gears it has to spin- a 504 would probably be a better choice for this reason

5) the automatic clutch is a bitch to tune... long story short if you want to build a 505, get a german 505/2b manual.

Re: Watercooled 75cc Sachs 505 Project

All this is good stuff. I would actually be starting with a 504, since that's the engine/bike that I just bought. I would almost certainly have to replace the crankshaft with something that accepts a variator, so i was thinking of just using a scooter crank, or a peugeot or motobecane crank.

I actually think the biggest problems are:

1. The Sachs 504 engine mounts, but i suppose there must be a way to reinforce them. I'm only going to be using the front end of the engine anyway, so i could just drop anchors through the case.

2. Modding the frame to accept either a Wariator-spring pulley or a scooter clutch attached to a shaft with a drive sprocket on the inside.

So, take apart a Sachs 504, dump out everything inside it. Take a crank of the appropriate conrod and stroke dimensions, that has either a splined or tapered shaft on the drive side, and use bearings that will match it to the 504 case. Fill in or cut away the case volume to match the crank pucks.

Build up the sides of the case if necessary and match the ports to the kit. Drill and tap new cylinder stud holes. Mount cylinder to engine.

For the variator, chop away the clutch housing portion of the case so there is room for a variator like an Er3 or a Multivar. You could mount the spring pulley and clutch either through the empty space behind where the drive sprocket used to be, or through the 505 pedal shaft hole. I would like the keep the clutch thing off the frame if possible.

The more i think about it, the more I just want to plonker it down into a heavily modified motobecane AV10.

Re: Watercooled 75cc Sachs 505 Project

I don't know why I keep reading this thread. It does nothing but hurt my head.

Re: Watercooled 75cc Sachs 505 Project

that video of the 130cc sachs being ridden on old European dirt roads had me scared shitless.

Re: Watercooled 75cc Sachs 505 Project

The 130cc Sachs is peaking out at around 80kph(50mph), it looks like. So the gearing on that thing is way out. With the way he has trouble keeping the front end down in the vid, some sprocket madness could probably propel that bike into the 70mph zone with power across the gears.

Is that a Vespa scoot top end on there? Sure as hell looks like it. I imagine the compression ratio would be crazy with the conversion from Vespa cases to Sachs cases.

Re: Watercooled 75cc Sachs 505 Project

woof, you guys aint kidding about this. I think the sachs case has a clutch side bearing lubricated by crankcase oil. minor, after everything else, but could be a problem.

i still think it would be way easier and more productive to just get a 505/2b. they are cheap on ebay.de.

Re: Watercooled 75cc Sachs 505 Project

Just a little input;norwegian version of Sachs watercooling.

It runs like..........


Re: Watercooled 75cc Sachs 505 Project

I've done the manual shift bikes. F-that. Variators. Also, the clutches can't take the abuse of 5HP kits and this kit is a 11-15Hp kit, and you can't get proper replacement parts for the two speed clutches..

Re: Watercooled 75cc Sachs 505 Project

So, I've slept on it, and thought of something.

if you are going to really hack together something why start with a sachs? Why not a 80 or 125cc scooter or dirt bike motor that already has water cooling, a crank and gearset or variator that already fits?

You know why?

Cause that's the pussy way out. Don't forget it. Anyone with enough money can buy something fast. The only challenge in that is getting the money.

Re: Watercooled 75cc Sachs 505 Project

I can't decide which I am more interested in at this point: a crazy kit or a variated sachs mod. I think I am going to try and get the variated part to work first, hopefully using the stock crank, but I have my doubts on that. I think that I would have to use a 505 case to have enough room to keep the clutch on the engine and off the frame of the bike.

Does anyone have any input on adapting 505 engines into 504 frames? Or can i just get a good picture of the left sides of a 504 and 505 case?

Re: Watercooled 75cc Sachs 505 Project

I went out to the shop for pictures tonight. This is a 504 and 505 case opened up sitting next to each other, so you can see the differences.


Re: Watercooled 75cc Sachs 505 Project

here is a 3/4 view of the top half of a 504 from the front- piston side.


Re: Watercooled 75cc Sachs 505 Project

top half of the 504 from the back


Re: Watercooled 75cc Sachs 505 Project

bottom half of a 504 from the front.

I also measured the clutch side of the crank and the shaft measured 11.70 mm The inside of the gear that the clutch disks ride on measured 11.65mm, and it still fit, so I'm not sure how accurate my digital micrometer is. The internal gear reduction is 4 crank revolutions to 1 sprocket revolution.


Re: Watercooled 75cc Sachs 505 Project

Photo of the clutch side of a 504 and 505. The top and bottom mounts line up vertically, but not horizontally. The 504 mounts are much closer together, so if you wanted to put a 505 where a 504 was, you would have to extend the lower mount, the engine would be lower in the frame, and you would probably would need to drill a hole for the second upper mount.

To put a 504 where a 505 was, the front top mount would be used, the engine would sit higher, and you would at least have to drill a mounting hole for the rear mount.


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