Re: Sachs 505 c/d Debate

chad burke specifically told me the connecting rods were different lengths, and i've never known him to be wrong about anything moped related. If the strokes are different, either the piston deck height or the connecting rod, or both, have to be different, or the compression ratios wouldnt be as close as they are. I'm pretty sure the distance from the crown of the piston to the crankcase on these engines is different, with the A being shorter, so in order to achieve the same compression ratio using a D jug on an A case, you'd need to machine the mating surface of the jug down. I've got access to several of these engines at the shop, its just finals week right now and i dont have much time to go in and measure everything. i'll get to it one of these nights.

Re: No Kit

can you make a stronger clutch?

Re: Sachs 505 c/d Debate

just ran the numbers, using compression ratio numbers, the piston-to-head clearance on the two cylinders is different by 1.1 mm, meaning the D piston either is 1.1 mm higher at the top of its stroke, or the D cylinder is shorter.

Re: Sachs 505 c/d Debate

ok, so there is a little discrepency between opinions.

Re: Sachs 505 c/d Debate

"Here is a link with technical specs":http://home.wanadoo.nl/harrytimmermans/engels.htm

Re: Sachs 505 c/d Debate

I would agree with the stroke being Dependant on the crank. It is crazy that they are not better documented like Puch.

Re: Sachs 505 c/d Debate

yeah, we had that data posted earlier, it doesnt have the con-rod lengths, the piston deck height, or the cylinder height. the piston height + con rod length could combine to the same with both engines, but the athena we built this summer has super low compression on an A engine, and i'm thinking its because of a significant descrepency in heights.

this type of stuff isnt an issue for puch, because all their engines use the same stroke/con rod/pistons.

Re: Sachs 505 c/d Debate

The stroke difference is 2mm so the deck should need to be lowered 1mm. The 70cc kit looks like it comes with a spacer that the 80cc does not. It could be the case that you use the spacer with the "D" and not the "A". 1mm could be corrected for by leaving out the base gasket. I would like to try to find instructions for that 70cc kit to see if this is the case.

Re: Sachs 505 c/d Debate

hmm thats a good idea.

it seems really silly to me that they would use two different con rod lengths, mostly because the forged con-rod is like, the most expensive piece of tooling for the whole engine, and i doubt they'd bother making two sets of tooling. my curiosity is killing me, i'm going to have to investigate this tonight.

Re: Sachs 505 c/d Debate

The "D" cylinder is shorter.

Re: Sachs 505 c/d Debate

I'll try emailing moped warehouse about the 70cc kit. If that metal gasket is a 1mm spacer it will answer a few things. Mind you this is all conjecture but it does seem to make sense.

Re: Sachs 505 c/d Debate

You know this thread was kind of derailed by mbartell, we have these same conclusions about head size, porting and crank length like 20 posts ago.

Re: Sachs 505 c/d Debate

thats what i figured. so the difference is made up by a shorter con rod, shorter piston, or both?

Re: Sachs 505 c/d Debate

I think the difference is not made up for but simply results in a 10:1 compression ratio as apposed to 8:1

Re: Sachs 505 c/d Debate

damn it if that is not exactly what i was thinking when i saw those 70cc kits on mopedshop. 2 different base gaskets.

Re: Sachs 505 c/d Debate

yeah, that makes sense. so putting an a jug on a d case (not that you'd want to) would result in the same CR as the D. The 70cc is probably higher compression than the 80cc so it needs a shim when its run with a D engine, so as to not bottom out. The 70 is probably meant for both, whereas the 80 is meant only for D engines.. of course it is double-drilled to fit both.

now onto the clutch, i haven't had a chance to tear down the blown up G3, does anybody know what commonly fails on these? is it the little teeth on the fiber plate? that seems to be the only weak link.. if so i think i might have an idea on how to fix it.

Re: Sachs 505 c/d Debate

It has been said several times over in this thread, but the connecting rod is the exact same length in all motors. The position of the con-rod on the crankshaft webs make for a longer stroke.

The 'D' piston skirt is shorter, but the position of the wristpin and top the piston is the same as the others. The port work is what differentiates the top ends. All can be ported for maximum potential, as well as pistons can be modified for maximum potential.

_The 70cc kit looks like it comes with a spacer that the 80cc does not._

Neither of these kits comes with any 'spacers'. A thicker gasket, but that is not enough to make the difference of hitting the piston at TDC on a 505/D.

We've had an 80cc kit going 55+ easy in Seattle on a 505/A, 505/D, 505/2B and 505/3B. We've had the 70cc going 45 with the stock carb upjetted on both a 504/1A and 505/1A,B&D.

You guys are really making this way too complicated.

Re: Sachs 505 c/d Debate

thanks a bunch brendan for weighing in on this.

you had a 80cc running 55 on a 'A' engine? even with the shorter stroke/lower CR? did you have to deck it down a mm, or was it just slapped on? ( i assume some porting was done)

Re: Sachs 505 c/d Debate

But it only needs to be 1mm, could the thicker gasket not make that difference? the problem is not so much a matter of mechanical collision in my case but the resulting crummy compression ratio.

Re: Sachs 505 c/d Debate

This is too much fun!

Re: Sachs 505 c/d Debate

The compression would be the same, but there would be really really tiny ports.

The awnser is pretty simple- there is room for the extra piston travel in most if not all of the cylinders. Take a sparkplug out, and look at how far the piston is from the very end of the sleve when at TDC. Matter of fact a well worn cylinder will have a very defined lip at the top end of the piston's stroke. The D gets a lot of power from that extra stroke. It's the only way to adjust the compression and squish area of a sachs jug. Diffrent spacing between the cylinder and engine case would change the port timing.

I'm trying to make sure that it all gets recorded right. Hard to validate things on the internet, especially when people don't measure, use diffrent terms, or are thinking of an entirely diffrent engine.

Re: Sachs 505 c/d Debate

Sorry i cant resist, but if i ran a 70cc kit on my 504/a ( yeah, 504 dif bike ) and the stock carb, whats a good starting point for jetting?

Re: No Kit

stronger clutch= more plates

if there is a way to shove another fiber and metal plate in the clutch, you would gain 2 more bearing surfaces (both sides of one more metal plate) What i've been thinking is that you either go with thinner metal and fiber plates to get more in there, or you make a longer center for the additional pieces.

Problems- thinner plates would be weaker

there may not be room for another pair of plates.

Re: No Kit

Sure, decking the base of the cylinder would change the timing slightly, but it could easily be made up for with porting. You'd get a built in 1mm advance on the intake port, and 2 mm retard on the transfer and exhaust ports, which anybody with the expertise to deck the head properly could easily adjust with a grinder.

Re: Sachs 505 c/d Debate

Hold on hold on Andrew we'll get to that, I wanted to comment on the strength of the clutch teeth themselves.

I've just compared three clutch baskets, one brand new, the other with 3396 miles, and the last with 7450 miles. Not much difference at all between the first two except the 3396 one has some slight glazing on the clutch basket walls, quite good. The last one with 7450 miles is showing some more glazing on the walls compared to the 3396miler and the basket itself is discoloured, you can see some clear signs of wear on the teeth of the clutch but it still grooves nicely with the main gear, there is no noticeable play between the teeth.

As for the clutch basket internals they are a different story. The new one of course, looks perfect. The 3396miler has the clutch disks themselves feeling slightly more pliable and there's a measureable gap between the disk at the clutch arms, about 0.5mm, everything else looks pretty much the same as the new one including the plates.

On the 7450miler the clutch disks have quite noticeable play between the clutch basket's arms, a little more than 1mm, the ballbearing basket at the bottom of the clutch is easier to twist and bend and the cluch plates are discoloured (although this may be due to wrong transmission fluid).

I really don't think that the clutch basket or its teeth are weak in any way, the one to consistently look shitty as the miles creep up and up are the clutch disks. I've had a 64.5cc kit on my clutch basket for two years now and about 2000 miles with zero change in the wear on the teeth and I tear apart all my motors twice a year. If anything goes and goes fast on the Sachs clutch it would be the disks.

Re: Sachs 505 c/d Debate

hmmm all good info. i can feel my knowledge growing (remember those espn commercials)

the main concern i have with the clutch is this 80cc kit is going to go on Clint's G3 pretty soon and the stupid bike already blew up one clutch with just the stock D engine, i think the heavier bike is going to absolutely crush clutches once that kit is on there. Expect to see some fancy sachs clutch shit coming out of milwaukee in the near future...

Re: Sachs 505 c/d Debate

yeah, if the d was shredding clutches , the 80cc mofo is gonna spin em right out of the case dude.

back to that jet size LOL

Re: Sachs 505 c/d Debate

I have a Balboa with a 505/D that I'm about to tear apart and dismantle and completely rebuild into a monster. Just trying to get all the parts together before I drag the bike out of West Seattle's garage and into my kitchen/Phil's shop and work on it over the winter. This thread is really informative.

Re: Sachs 505 c/d Debate

I just noticed something else, the carbs came in 12mm and 10mm sizes right? Well there's another difference inside the 12mm carbs. One of my engines has a 12mm carb works much like the Encarwi diaphragm carb, it doesn't require a needle pin to operate well.

I just picked up an identical 12mm square bing to clean it up and inside it uses a much longer throttle barrel (same width) and it uses a needle pin with 4 notches to adjust midthrottle fuel mix.

Numbers on the side are 85/12/101 A, i recognize these numbers on other Sachs engines so maybe the other Encarwi-styled square Bing is the weirdo one with no needle pin.

Re: Sachs 505 c/d Debate

i have one of those crazy no pin carbs.

I bet that the one on the 505 with the square head is one too...

actually i sent that other non needle carb to someone by mistake, gotta get it back.

But yeah this has been an info packed thread.

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