1978 Sachs - used to start with one crank. Won't start

New here, please be gentle. Bought a 1978 Sachs Surburban, cranking over and running fine until about a week ago. Went over original schematic which showed 3 wires coming out of the magneto, the magneto on this one has 5 wires and the green wire for the front/rear brakes was loose and hanging detached from the terminal block, have those reattached now and the last time it started all lights including brake lights were functioning as they should.

The guy I bought it from said it might be a carburetor issue, has an aftermarket carburetor on (pics attached). The engine did get a 70cc bore and piston and there's currently no air filter on it. Didn't stop it from starting up previously. There is confirmed spark, gas tank is full, petcock works and fuel is flowing. He said the compression lever is working fine and I've checked the bottom float and the transmission for proper movement and transmission fluid.

Any ideas to get this running again? I'm going to try removing all wiring from the terminal block except essential like kill switch just to see if I can get it to crank over. Only 636 miles on the odometer.

Sachs (2).JPG
Sachs (3).JPG
Sachs (4).JPG

Re: 1978 Sachs - used to start with one crank. Won't start

Ľ̷̝̽͒i̶̛̼͑͠ȁ̸̧̛̽m̵̻̟̯̀̅ ̷͎̙̽̊F̶̲̺͑̓ F /

What jet are you running? often times people don't jet when putting on a cylinder kit, and that causes issues with starting and running. Also, put in a new sparkplug, since sometimes they will spark when outside of the engine, but not under compression. Run an air filter as well, its just good peace of mind knowing your engine won't be killed by a loose piece of gravel

Re: 1978 Sachs - used to start with one crank. Won't start

I like air filters as well, is there spark? if not then clean your grounds. if there is then squirt some premix in the hole to see if it'll fire for a few seconds, if it does then clean your carb.

Re: 1978 Sachs - used to start with one crank. Won't start

There is spark, yes. Cleaned the plug. I've squirted premix in, still won't fire.

@vespaciaobrapwrap

Not sure what the jet is, I'm just learning about engines.

This moped started on the first crank just over a week ago. Seller told me a smaller carb may do the trick but said to post here for some feedback.

Re: 1978 Sachs - used to start with one crank. Won't start

Are you running a 70cc kit with a stock pipe? Smaller carb will not help, might make it worse

Re: 1978 Sachs - used to start with one crank. Won't start

If you don't know what jet your running you are lucky it ran at all before.

Tackle the jetting problem before you seize the thing. Hell maybe you already did and that's your problem now.

Mopeds are two strokes, meaning fuel and and oil, as in lubrication are mixed. Too lean and your engine isn't recieveing lubrication. And you can seize.

Pull the cylinder and check the bore Piston and rings before continuing troubleshooting.

Re: 1978 Sachs - used to start with one crank. Won't start

Yes, 70cc kit the seller put on. It was turning over fine the 3 or 4 times I tried. The only thing I've done is consult the schematic and attach the loose wire from the magneto to the terminal block to see that the front/rear brake light switches were working. I haven't rode it, just cranked it over to test lights and switches.

Re: 1978 Sachs - used to start with one crank. Won't start

> Aaron Blair Wrote:

> -------------------------------------------------------

> If you don't know what jet your running you are lucky it ran at all

> before.

>

> Tackle the jetting problem before you seize the thing. Hell maybe you

> already did and that's your problem now.

>

> Mopeds are two strokes, meaning fuel and and oil, as in lubrication are

> mixed. Too lean and your engine isn't recieveing lubrication. And you

> can seize.

>

> Pull the cylinder and check the bore Piston and rings before continuing

> troubleshooting.

I wouldn't have bought it if it didn't run. Seller told me a 50:1 mix, it's what I measured out and filled the tank with. Fuel flow is fine, seller came over and checked - he works on cycles but I've pestered the guy enough. Forgot to mention, after attaching the green wire from the magneto to the terminal block, it would turn over and start stalling out after 5 seconds. I found the fuel line had come off the carb (no wire clamp) but reattached. That's why it was originally believed to be a carb issue. (edited)

Re: 1978 Sachs - used to start with one crank. Won't start

have u cleaned the carb yet? might be a fouled plug.

Re: 1978 Sachs - used to start with one crank. Won't start

I opened the carb, checked the float - it was all clean. The spark plug I cleaned. When I take it out of the cylinder it usually has a light coat of oil on it. If you mean the rubber o-ring in the carb that was fine and intact. (edited)

Re: 1978 Sachs - used to start with one crank. Won't start

If it starts for a little bit that's moving in the right direction, to clean your carb take the jet off, use brake cleaner and blast air thru all holes. make note of jet size while u hold up to light.

New plugs r cheep and eliminate a common error, no start from plug being fouled.

Re: 1978 Sachs - used to start with one crank. Won't start

Timings off

Re: 1978 Sachs - used to start with one crank. Won't start

> pat splat Wrote:

> -------------------------------------------------------

> If it starts for a little bit that's moving in the right direction, to

> clean your carb take the jet off, use brake cleaner and blast air thru

> all holes. make note of jet size while u hold up to light.

>

> New plugs r cheep and eliminate a common error, no start from plug being

> fouled.

The last time it started it was for a little bit then was stalling out, that's when I found the loose fuel line going into the carburetor. I can get carb cleaner and a new plug today. Still just wondering about the jets. There's an adjustment screw on the carb, but from the one video I watched the jet is inside the carburetor and looks a little different. Anyone know what this screw circled in red is for?

Sachs (3)e.jpg

Re: 1978 Sachs - used to start with one crank. Won't start

idle speed, use brake cleaner to clean carb and please dont ask why.

Re: 1978 Sachs - used to start with one crank. Won't start

Guys sells you a lemon and his customer support is to send you to MA?

What a swell guy.

I like the timing idea as well. Something may have moved if the seller was working on it and didn’t secure the points or stator plate.

I don’t know how long that 70cc Kit has been on there. If it’s new, maybe the head is a little loose? My kit blew its head gasket right away when it was new. (Not a big deal on Moped, so don’t worry).

Don’t feel bad about bugging the seller. You did nothing wrong. The decent thing would be for him to help you get the “running” moped you were sold running again.

But, you certainly are in the right place to learn to fix it yourself.

Re: 1978 Sachs - used to start with one crank. Won't start

I only paid $250 for it, tinkering project. Bought a new plug and will clean the carb today. The wiring on the terminal block is back to how it was when I bought it. Just have to gap the plug after I eat lunch and see if the new plug solves the issue.

Re: 1978 Sachs - used to start with one crank. Won't start

> pat splat Wrote:

> -------------------------------------------------------

> idle speed, use brake cleaner to clean carb and please dont ask why.

I used carb cleaner and cleaned out the carb. Put a new plug in with .025 gap, halfway between the manual spec of .020 inch and the old plug which had a .030 inch gap. Does anyone think the .030 gap was done to accommodate the 70cc kit?

It fired up, when I opened the throttle there was a pop and it smelled like a firecracker and the exhaust dropped off the cylinder. Reattached that and it does start up now and run idle. I'm curious if that exhaust is going to drop off while riding.

Re: 1978 Sachs - used to start with one crank. Won't start

maybe start at the top and post what you've learned about your moped. 250 is cheep for a kitted bike, basically the cost of the airsal kit. good luck.

Re: 1978 Sachs - used to start with one crank. Won't start

I notice a light white smoke coming out of the exhaust now while it's idling, didn't recall that before but wasn't looking for it. Does it mean there is too much oil in the mix?

Re: 1978 Sachs - used to start with one crank. Won't start

Fun fact : 2 strokes smoke . ;)

You're likely fine .

Re: 1978 Sachs - used to start with one crank. Won't start

Man, I wish I'd seen this earlier, it all smacked hard of a fouled plug - especially that wiring bit. The brake light wires are necessary for the ignition to spark, likely having that dead and fuel going in but no spark was enough to end your old plug. there's not really any reliable way to clean a plug either (except maybe sodablasting it or something), definitely want a new one. it's worth keeping a spare with you

Re: 1978 Sachs - used to start with one crank. Won't start

Bigger kit takes more to compress

Re: 1978 Sachs - used to start with one crank. Won't start

Kevin Bishop /

Seller works on bikes and the exhaust falls off. Yep mopeds

Re: 1978 Sachs - used to start with one crank. Won't start

> Kevin Bishop Wrote:

> -------------------------------------------------------

> Seller works on bikes and the exhaust falls off. Yep mopeds

Ha . So , 2 + 2 doesn't always make 4 ? ;)

Re: 1978 Sachs - used to start with one crank. Won't start

who has had a sachs and not had the exhaust fall off haha, i weld little washers on the headers and spring mount em all now. last time i didnt do that a budddy was riding it and the pipe dropped, caught and tried to pole vault the rearend

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account