Sachs engine won't start

Hi, just 24 hours ago my moped was working. But after a long day of heat, it won't work anymore. The engine seems like it is trying to start but like "nothing catches" and as soon as I let go of the clutch it shuts off. Please help me solve this. Thanks.


Re: Sachs engine won't start

Sorry kind of basic here: is it on? have gas?have spark?

If it got really really hot you may have had some wires melt to the head. I had it happen, and it killed it instantly.

Re: Sachs engine won't start

No that's fine, it was on when I was trying to start it. The tank is full but I don't know if the carb is taking any fuel in (the fuel line had a bubble in it but I got rid of it and it still didn't work). I do think it's not getting fuel but when I disconnected the fuel line from the carb and pointed it down it flowed pretty freely. It's got brand new spark plugs so I don't think that's the problem. I'm really frustrated with this because I bought the moped as a father's day gift and it already isn't running. Any advice would be helpful. Thanks.

Re: Sachs engine won't start

did you have the correct--fuel to oil ratio...

has to be some reason it was running hot..

my old 1980 102sp--takes 2.5oz of oil to 1 gallon of gas..

good luck----------later...

Re: Sachs engine won't start

Hi, yeah, it has the right mixture, same as yours (2.5 oz of 2 cycle oil to one gallon gas). But earlier in the post when I said it was hot, I didn't mean the moped was hot, I meant the weather was hot and I thought that the hot weather may have affected it. When it ran 2 days ago it ran fine, but since the weather has been hot it hasn't started again. Maybe that may help a little. Thanks.

Re: Sachs engine won't start

try a shot of starting fluid--see if it runs..

if it does then you might have a dirty fuel filter..

lossen the carb drain screw to see if your getting fuel to the carb..

should be located on the bottem of the float bowl..

that is if you have that type of carb..

then again it could be just a bad spark plug--somtimes they don"t fire after being abused--they build up a black residue thats hard to clean off inside the innerr part of them and they just won"t work..

they fire outside the engine--but not when you screw it back in...

its common for that type of missfire on chainsaws....good luck..

Re: Sachs engine won't start


I have a sachs too. To make sure mine will start after every winter, I do the following.

I take the spark plug out, make sure it's clean and dry. You can ground it to the head to see if you are getting nice blue spark.

Take out all of the old gas, but I drain it all out before winter.

Take the carb bowl off and check for gunk, be careful of the gastket. I know you're supposed to get new ones, but sometimes you can get by.

Make sure your jets are clear, blow some air through it to make sure. If it's clogged, you won't be getting any gas.

You can also check your fuel valve, but it sounds like you have that figured out. An inline filter isn't a bad idea-just a tip if the moped is older.

Put it all back together and try to start it. If it won't go, and you already have spark, you must not be getting the gas.

Either starting fluid, or I just take a super small amount of mixed gas and pour it into the head. NOT a lot. Then if it runs for a few seconds and dies, you know what's up.

By the way, does your moped have pretty poor acceleration? Mine is real slow, but it tops out at about 31-32.

Re: Sachs engine won't start

Hey kyle, thanks for the information. I am going to try to work on the moped either friday or saturday cuz I have a lot of things to do this week. But before I do, I have to let you know that I don't know too much about mopeds. This is my first and it was used. So I don't have a manual or anything. Do you mind telling me where the carb bowl is and how to take it out? And where the gasket is located and what it looks like? Also, what exactly are the jets and how can I pour gas-oil mixture or starting fluid into the head? I know these are pretty stupid and basic questions but I never really have had a major problem with any motorized vehicle or transportation because I usually buy them in good condition. Thanks in advance.

Re: Sachs engine won't start

Oh yeah, and kyle, to answer your question, mine tops out at about 25-28 mph (don't know for sure cuz the speedometer is broken). It accelerates poorly from 0-10mph and then it kicks in and accelerates pretty well (that is when it was running a couple of days ago).

Re: Sachs engine won't start

Alright, well, to anyone that has been helping me out or wants to help out, I think you guys help me realize the problem. I didn't really do much yet, cuz I plan on doing most of the work on the weekend but I found that the fuel flows well from the tank, through the petcock, and through the fuel line, I don't think it flowed well from the fuel line through the carburetor. The reason is that I took off the plate to the float bowl (I think that's it) and it was about a 1/5th full of fuel, I let it spill out and then reattached the fuel line to the carburetor opening and the fuel did not flow at all down the carburetor (i don't know if that's how it works) when the moped was off. I pumped the button to push the fuel (the "ping" button) and after I did that fuel started squirt out of a hole next to this "ping" black button. Nothing went into the float bowl. I then reattached the cover and then tried to start the moped and I noticed there was a bubble in the fuel line and it wasn't moving, so I figured fuel wasn't flowing. This is my first time trying to repair a moped but I plan on making a more detailed description with links to pictures of my moped and its parts so I could be more clear (I would do that now but I am late for a meeting with some old friends). But for now, if anyone could tell me how to fix this and if my diagnosis even makes sense, please let me know. Thanks (and I will create a more detailed description with pics soon).

Re: Sachs engine won't start


A bubble in the gas line isn't a huge deal, you can fix that pretty easy. Just bleed the gas line.

Ok carb work: If you go to and check out the "Sachs" page, you'll see a diagram of the Bing Carb. The jet are numbers 22 and 23. Make sure air flows through those. That black button pushes the float down, simulating that the gas level in the bowl is low, thus gas will start to flow from the tank to the bowl. When the level is high enough, a small cone shaped needle that is attached to the float, fills the jet and stops the flow of gas.

That jet, which I can't remember if it comes out or not, needs to be clear of gunk. The needle needs to be in good shape too, otherwise gas can leak if it's not coherent and smooth.

Just examine the carb. Anywhere you see small holes where it looks like gas should flow, make sure you can blow air through them. An air hose works great.

There is carb cleaner out there you can soak the carb in, but you can't have any gaskets, (which is the cork part between the two metal parts, #'s 7, 21 ) plastic or rubber sitting in the solution. After you soak it wash it with hot soapy water, rinse thoroughly and air dry with the air hose. NO WATER ANYWHERE should be present when you put it back together.

Just have a nice clean, free-flowing carb, and you should be getting the gas.

Did you try to turn the engine over while having the spark plug (wire attached) grounded to the cooling fins of the head? If you get spark, you should be in business then.

Yeah, so to get more top end out of my moped, I enlarged the plastic, cylinder shaped part of the air box with a hot, over sized rod. I made the shape of it like a trombone bell, so that the air flows faster over the curve. That allows more air to flow in. I also put some air scoops out of the intake silencer (gray part which holds the air filter). I am 170lbs, and it reaches 30-32 with me on it. Now I need to get my Tomos shifting into second.

Best of Luck,


Re: Sachs engine won't start

are you guys talking about the Sachs 505a or 505d engine?

Re: Sachs engine won't start

Alright, well first Kyle, thanks so much for that valuable information and second, to answer "maxmagnem", I don't know if it's a 505a or 505d engine, I don't know how to check really. And Kyle, I learned alot from the mopedjunkyard diagrams you told me about. Now I am understanding things a little bit better. There's three reasons I haven't checked the spark yet. First, the previous owner had installed new spark plugs. Second, before when the moped was running if I filled an empty gas tank I could see fuel from through the fuel line and reach the carburator and now when I fill the tank I see no movement and no fuel going to the carb so I figure there is something clogged. Last, I don't really know how to check a spark plug safely, I haven't ever done anything at all related to any motorized transportation. I don't know how to ground it (I have no idea what to do) and I don't know how to start the engine and see spark at the same time (cuz it's a pedal start, which I'm sure you knew, and I don't understand how someone can pedal and check for spark at the same time). I know that sounds pretty ridiculous but it's true, I don't know how to do it. It's like 2:45 AM and I finally am going to start work on the moped. I did look at some stuff earlier this week and got a little curious and took something off of the moped and put it back on. I don't know if this could do any damage but I just wanted to make sure. Well, if you have time to do this you can log into a website to see what I am talking about. In order to see a pic, just go to , then in the email address space log in with The password is mopedarmy. Then log in and go to the album dated 7/01. The pics are numbered 1-9. Well, in pic 9 I took off a covering to this device cuz I thought this was the carb (but after looking at the mopedjunkyard I realized it wasn't). There was a lot of oily fuel in it and I dumped it out and put the covering back on. What is this general device in the picture? And one more thing, how the hell do I put starter fluid in the cylinder head to check to see if it is a fuel problem. Like where would I pour in the fluid and how much (haha)? Well, anyways, I am going to go try to clean the actual carb and I'll see if I can do it for now. I do appreciate you helping someone who knows so little. Thanks again.

Re: Sachs engine won't start

Just letting you know that I changed my mind, it's too late at night to work on the ped so I will work on it in the morning.

Re: Sachs engine won't start

Just checking to see if this pic shows on the post, if not you can still see pics of my ped on

Re: Sachs engine won't start

Maybe this pic will show, I don't know.


Re: Sachs engine won't start

Alright, to see the pic of the device I don't know much about, just click on the attachment in the previous message. That should be easier than logging on to my snapfish account.

Re: Sachs engine won't start

Andy (amodo) /

Hi, well today I tried to remove the carburetor and pretty much didn't know how. It's attached to the airbox with tiny screws that seem impossible to reach. Also, I couldn't really remove it from some big pipe that was attached to the back of the cylinder head. And when I tried removing the top of it where that cable comes in, I didn't know if I was supposed to pull the cable out or what. Can you guys give me a little more advice for this (I don't know jack about mopeds). Thanks. (Does anyone know where I can get a manual for a 1977 Sachs moped?)

Re: Sachs engine won't start

Just wanted to thank everyone for all their help. But I've been an idiot, it just needed a new spark plug. Now it runs like new. The reason I didn't check the spark plug was becase the spark plug is only 2 weeks old and has about 50 miles on it. But anyways, I am so glad. Thanks guys.

« 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