MOPED ARMY

<img src="http://i98.photobucket.com/albums/l258/andrewhed/nog%201-16-2007/sachsquestionone.jpg">

how many times can I say that the square heads are all exactly same.

The 'D' reference has nothing to do with the cylinder, and everything to do with the bottom end and crankshaft.

505-1A:http://home.wanadoo.nl/harrytimmermans/5051ab.htm

505-1D:http://home.wanadoo.nl/harrytimmermans/5051d.htm

I noticed this today from a link in the wiki, If you look at the specs you'll notice that the "D" has a 2mm longer stroke, thus the "A" having an 8:1 compression ratio and the "D" a 10:1

so the A engine gets either an A or a B cylinder (taperd fins)

the D engine gets a D cylinder (boxy)

the main difference is stroke length

am i correct?

are there different pistons?

what does C mean?

are the clutches/internal gears the same?

is the 'a' what is called a 25 mph cylinder

the 'b' called a 20 mph cylinder

and the

'd' the 30 mph cylinder? i've seen the stickers on the bikes, and wondered if thats what people are referring to.

what cylinders/pistons came with PI gaps and which ones had FG gaps?

if people answer all this shit i'll type it up and wiki it, this is the kinda stuff i take for granted knowing about puchs... other brands i have a lot to learn about.

the letters can't be the only thing, and D's aren't the only 30mph bikes, I recently sold a Westlake with a 1/A and it was marked on the left fork tube with a 30mph sticker, and it did a solid 30 stock

What is the point of putting a speed rating on a motor it that has nothing to do with the speed of the bike?

and most importantly, which sachs mopeds come with the d motor stock? Just balboas and eagles? what about G3s?

this is super informative.

All D cylinders have two piston rings as does all the 504 & 505 line of engines, if you observed one with only one ring it must have been a substitute.

Other differences that I've noticed between the 47cc "A-D" engines are the main gear weights, see the "spoked" main gear on the right? Well that is from a 47cc 505A and it is substantially lighter, just by the feel of it in my palm would suggest 40-50grams lighter. The one on the left seems to be the standard for 505d's, probably built a little tougher to handle the extra 1HP the cylinder puts out.

My current plan is to outfit one of my other stock 505D bottom ends with this lightened main gear and observer performance changes. I've been through 16 Sachs engines so far I think I can dismantle the things with one eye now ahah.

I have some more pics to post so stay tuned. It would be really nice if someone could build a few pages in the mopedwiki i'm totally inept at it

Here are pictures of a D cylinder and A cylinder. They are compared:

D cylinder has a wider and slightly taller intake window than does the A cylinder

D cylinder has a wider and slightly taller exhaust port

transfer port shape are virtually identical BUT the A cylinder has the transfer ports entering the cylinder at about 4-5mm farther into the cylinder compared to the D cylinder

base depth is reduced on the D cylinder by about 0.75-0.90 mm (accounting for compression difference??)

the piston windows are shaped differently and the D windows are wider by 4.5mm

their bottom ends have identical cranks but the rods do appear to have varying lengths

I took the number of rings from a spec sheet but that's not to say it didn't change when the single ring wasn't holding up. The "D" piston is rather surprising seeing as how it is a higher compression engine. I wonder if there is much difference internally between the two cylinders? My first theory was when looking at the data the "D" had a 2mm longer stroke and that the main difference was a 1mm offset on the crank as pushing the piston 1mm farther into the cylinder could result in the dramatic compression ratio change.

No the rods are not the same they is a few millimetres difference, it would be a terrible idea for someone to think they could swap an A cylinder to a D bottom end not just because of the different stroke and piston size but the size and timing of the ports. A single millimetre difference could throw an otherwise harmoniously running engine of balance and the transfer ports entering the cylinder on the D engine are several degress advanced compared to the A cylinder. It used to seem so simple at first just swapping this with that etc. etc. but those Germans put much more effort into restricting and making these engines incompatible with each other than we realized. The parts that really seem consistent are the internals such as the cluch, crank and gear. I'm very anxious to get started on that rebuild i'm planning: swapping the 505D main gear for the lighter 505A main gear, I expect torque and throttle response to go up and up but then again the sacrificed top end with less rotating mass...(sigh).

The A is only common in North America, in Europe the D is standard and since all the manufacturers are based over there it's more likely that their kits are meant for the D cylinder. Remember that Europe has very liberal regulations on power+speed for their small vehicles, tried selling to America and found out they had to restrict everything. Thus the 20mph to 30mph models.

I don't forsee any problems in buying a kit it should slap right on since you are changing the cylinder _and_ the piston. Your timing, however, will most definitely need to be readjusted. My timing is retarded by 1mm on the stator plate markings and everything worked out fine, but then again I upgraded a 505D engine. Let us know what happens and don't forget to post it up.

I'll have to order one. I forget that the de-tuned models are typically for the U.S. market. Those poor Honda PA50-Is

Thanks!

This is using an 80cc athena reedvalve kit. they run about 280 bucks, its not mine, one of the other guys in the gang. We built the engine and put it on a columbia commuter, quite possibly the shoddiest moped frame ever made. Its a good thing it only went 40 because the bike felt like it was coming apart at 30, and was actually. We decided to scrap the whole engine, put the kit on a D engine one of the other guys in our crew has, and part the bike out since the frame cant handle the 50+ mph that kit is capable of.

So one more question, then i'm done buggin' ya. Is there any difference between clutches from the a/d engines? I have a feeling we'll be needing that one out of the A engine after the D engine blows it's own clutch up.