If you own a moped, sooner or later you're going to need to work on it. Trust me on this one... Once in a while you may need to remove the flywheel or clutch. This can be tricky to do because as you try to remove the nut, the motor will want to spin. How does one stop the motor from turning, you ask?

Piston stop!

I'll show you how to use it.

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Step 1: Krusty Bike

So, this is the victim. It's a 1977ish Sachs moped. Adorable, isn't it? Believe it or not, this bike needs some work done to it. Clutch work. Apparently, Sachs motors have notoriously crappy clutches. If you have an impact driver, the job would be easy, but you don't, do you? Didn't think so. That's why you're reading this Instructable about using a piston stop. But it's okay. That's how we roll in the shire. Let's move on, shall we...

Step 2: Follow Duh Wire...

You're going to need to remove the spark plug. "But where is duh spark plug" you ask? Just follow your nose... to the wire that leads to the spark plug. It's typically the 7mm wire that runs to the front of the motor. Still lost? Take out your calipers and start measuring the wires and find one that's 7mm. What's that you say, you only have dial calipers that use the Imperial measurement system and not metric? Fret not, it should read 0.2756 inches. Aren't I a sweetheart! Anyways, pull the "boot" off from the sparkplug.

Step 3: Grab a Wrench...

We start by removing the spark plug from the cylinder head. there are a few different sizes of spark plugs out there, but 99.832% of mopeds use the 21mm type. At least I think it's 21mm. I forget. Anyways, put the socket onto the socket wrench, then onto the spark plug. Righty tighty, lefty loosie is a good rule of thumb.... unless it's a reverse thread. But spark plugs aren't a reverse thread. EVER! I'm pretty sure. So, yeah. Remove that naughty spark plug.

Step 4: Fancy Tools!

Here it is, the piston stop. Yes, yes... I've used this picture twice. Stock footage is what we call it in the industry. The FILM industry, not the industry you were thinking of. Let's stay focused here, okay? anyways, This is a homemade piston stop. It was constructed out of a bolt, an old spark plug and a nut. That's a whole different Instructable yet to be Instructabled. Now, lead the piston stop into the hole where the spark plug came out from. You may need to turn the flywheel a bit, thereby moving the position of the piston down a bit to allow clearance. Tighten the piston stop down by hand finger tight. Snug.

Once the piston stop is in place, turn the flywheel in the direction that you will be wrenching until the piston makes contact with the piston stop. And there you have it. You are now ready to start working on and cursing at your moped-super bike.

Have fun!