Troubleshooting Your Motor: Why Won’t My Motor Start? pt. 1

How many times have you hopped on your motorized bike for a ride, pedal, let the clutch out and… nothing? We’ve all been there, so it’s good to know what to look for to fix the problem and get you on the road. Here we’ll focus on two major issues we hear when riders can’t get their motor to start:

Scenario 1: My clutch is grabbing but the motor won’t start

Imagine you’re holding in the clutch, pedal your motor, and release the clutch. You keep pedaling and can hear the piston moving up and down in the cylinder, trying to start the motor but you’re not getting any power. What do you do?

1) Make sure all bolts are tightened down around your engine

Make sure all nuts and bolts are snug per maintenance instructions, including the cylinder head, manifold, and exhaust studs. If your studs aren’t tightened you can be allowing air leaks around your engine, which leads to a lack of compression. (Note: cylinder torque should be 10-12 ft/lbs)

2) Check the fuel flow in to your motor

Pistons move down the cylinder when the spark from your spark plug ignites the gas from your motor and creates an explosion that sends the piston back down the cylinder. If you’re not getting fuel in to your engine that explosion won’t happen. First, start by looking at the fuel line and make sure it’s filling with gas.

If the motor’s not getting fuel, make sure the gas tank is mounted above your motor (this motor’s gravity fed, meaning fuel travels downward in to the engine instead of being pulled in to the motor).

If it’s mounted correctly remove the gas cap of your fuel tank. If the fuel travels into the cylinder with the cap off it is an indication that your fuel tank is not breathing. When that’s the case, replace the gas cap with one that allows a slightly looser seal. If you do not want to replace the part, you can also drill a pinhole in the gas cap to allow the tank to breathe.

3) Check your Fuel Valve and Choke Lever

Fuel Valve: The Down position means the fuel is on; sideways means it is off. Always turn the fuel valve off when not in use to avoid flooding your motor. Be sure to also check the filter on the end of the fuel valve to assure it is free of debris and blockage.

Choke Lever: The choke is located on your carburetor and it’s used to warm up the engine. You’ll want to make sure the lever is lifted up when you start the motor: that means the choke is on. When your motor’s warmed up (you’ll hear the idle raise significantly), push the choke down to open the choke. Depending on the temperature in your area and the time of year, the choking time will vary. When it is warm outside you won’t need to choke the engine as long; in cold weather you’ll need to choke the motor longer.

Scenario 2: My clutch isn’t engaging the way it’s supposed to

Now imagine you hold in the clutch, pedal your motor, release the clutch, and instead of the engine starting the bike drags to a halt. What do you check?

1) Check the clutch cable tension

A small amount of free play is needed for your clutch cable to work properly within the clutch lever. Too much or too little free play and the bike won’t start. If you need to adjust the play slightly, you can do so on the barrel end adjuster at the clutch lever. Major cable adjustments can be done at the clutch arm with the clutch wire clip (or clutch cable stop).

2) Check the chain tension

Check the chain tension. An improperly adjusted chain tensioner can cause the drive chain to bind within the engine, leading to the chain snapping. Check that the engine chain is not bound around the drive sprocket inside of the engine. The play on the top of the chain should be between 1/4-1/2″ of play depending on the motor you have.

3) Check out the small and large bevel wheels for damages

Remove the clutch plate on the right side and inspect the condition of the small and large bevel gears for wear. Also check to see if they are flush with the motor.

 

4) If it’s still dragging, adjust the clutch

16 thoughts on “Troubleshooting Your Motor: Why Won’t My Motor Start? pt. 1

  1. Motor runs but can’t get the pop pop noise to go away. Tightening jet the fell out helped.plug looks good. No adjustments on standard carb to fix this.seems like not getting enough gas.better after worms up but still popping.cut exhaust tube and drilled holes in end still same.Help

    • Hey there, Scott! Where’s the popping coming from? If you’re experiencing backfire you could be getting an inconsistent spark, which could be an issue with your oil mixture or your some kind of defect within the magneto and/or the CDI.

  2. I am putting together and 49 CC 2 stroke motor and the chain is sticking to the motor sprocket, it looks like the chain does not want to fall right onto the sprocket it is sticking I do not know what to do. I did not have to cut or take out any links on the chain it fit right on without doing nothing and it is not catching any where around the motor sprocket its just sticking to the small motor sprocket sometimes it will just barely go on it I hope you guys can help me thank you.

    • Hey there, Mike! If you’re having issues with that chain not lacing around the drive sprocket, you may want to consider shaving the teeth of the drive sprocket. You can round the sprocket teeth and take them down a bit. Be sure to do an even job when doing so, that way your chain doesn’t knock against the case. Otherwise, one of those teeth can lift the chain and interfere with the engine sprocket, giving you the same problem you’re having now.

  3. Hey there I am having problems with my motor. Pretty sure it’s the spark plug seal. If you have any suggestions let me kno. For example I am getting the engine to pop and cycle but it’s lost almost all of its power. Thinking that’s it’s a seal on the spark plug preventing the combustion chamber to max compress the mixture. And the mixture is fairly lean. I fixed the muffler and still nothing.

    • From what it sounds like, you’re probably having an issue with compression due to a small air leak. Check to see if that spark plug seal is cracked or worn. If it’s not, check the top and bottom head gaskets to assure they’re not broken or worn down too much. If all of those components are in tact, we suggest taking a flashlight to your engine and looking for any cracks, breaks, or tiny holes in your cylinder or head to see if there’s anything you need to plug up or replace.

    • Sorry to hear that, Mary! When your bike is able to start, you can trust your compression and electrical components are good, so already 2/3 of the major components of your bike engine kit are in proper working order. Now it’s time to check the choke on your carburetor:
      First, make sure your choke is in the “Closed” position when you start the engine. If you have the choke “Open” when you start the engine you’ll introduce lots of air in to your cylinder, which will cool your fuel. If you fuel is not at the right temperature, your fuel will not ignite when the spark hits it.
      Leave the choke closed for amount a minute, then listen to your idle. When you run your motor, you’ll want to leave the choke on until your idle beings to pick up. When you first start the motor you’ll notice that it might run a little rough- but this is normal while your motor is warming up. After your motor is warm, you’ll hear your idle start to pick up and even out.
      Once your motor is warm, you’ll hear your RPM’s pick up pretty high- this means your motor is warm. Once it’s warm enough to run without the idle you’ll want to open the choke.
      If you open the choke before the motor is fully warm you may be able to continue running for a little bit, but eventually your motor might power down. This is because the engine is receiving lots of air which is throwing off the temperature of your fuel, so it cannot be igniting in order to keep running. But with a simple adjustment of the choke you should be good to ride for miles non-stop.

  4. I have a 66 CC 2 stroke motor the spark plug seems to not be getting any gas I keep trying to ride it and then checking the plug and it’s dry every time does anybody know what could be causing this?

    • Great question, Damon! If your plug’s bone dry chances are you aren’t getting any fuel in to your cylinder, so first you want to make sure fuel is flowing from your gas tank in to your fuel line. If it’s not, check the filter at the end of the fuel valve to make sure it’s clear of dirt or debris that could keep fuel from flowing.
      If the fuel is flowing from the tank in to the carburetor, then you’ll want to make sure your carburetor jets are clear so that the fuel is flowing in to your carburetor.
      If your fuel is entering the carburetor and your plug is still dry, check the head or any leaks in compression to make sure the compression is pulling fuel in to your cylinder. This could be a gasket leak or a pin hole somewhere, and if those leaks are addressed you should be able to get fuel pulling in to your cylinder.

  5. HI IVE GOT A QUESTION ME AND A BUDDY ORDERED 2 80CC MOTORS HIS BLOWS MY DOORS IM THINKING I GOT A 49 OR 66 AND THINK HE GOT AN 80 WITHOUT PULLING THE HEAD HOW CAN I TELL WHAT I HAVE ALSO MY MOTOR TRYS TO HIT THE POWERBAND BUT JUSTS JUMPS AND STUMBLES LIKE THE MOTOR ISNT REVING UP ENOUGHIT WONT MAX OUT ON THE RPMS ANY THOUGHT?

    • That’s something we actually hear a lot, and from what we’ve seen it’s really just a matter of inspection and tuning from out of the box.

      Now the only way to really tell if you’ve received a 49cc vs a 66/80cc is to disassemble the cylinder head and measure its cubic centimeter size, as well as measuring the piston. Most of the time when you aren’t going as fast as someone with the same motor it’s because there’s a couple of things that could be off:
      First you’ll want to check the compression on your motor head studs are at 10-12 ft/lb. If your compression is off your motor will not be able to run again.
      Second, you’ll want to assure your carburetor is properly tuned. To see how to tune that motor, just click here to view our tuning guide on how to get that carburetor back in shape.
      Third, you’ll want to make sure you’re breaking in your motor properly, with the correct fuel ratio and taking it easy on the motor. If you try to max a 2-stroke out straight out of the box chances are you’re going to burn the motor out before it gets a real chance to perform. This is often the reason a motor will sputter or jump in speed: if it’s not broken in properly there are going to be gaps in performance.

  6. 49cc motor kit. Has spark. compression. Sealed all gaskets just in case. Float bowl has fuel. Seems like not drawing gas to cylinder. Cylinder, plug, and piston look great. Was told did run when I purchased but been sitting over winter. At a loss. Any suggestions? Getting ready to test ohms. Thanks

    • Great question, Kevin! Like any engine, if you plan on not using it for a while you’ll have to winterize it. If you don’t it’ll go the way of all motors that sit for a long time: they’ll begin gather deposits that won’t combust or even run.
      What we recommend for a motor like that is to disassemble it and thoroughly clean it out. You’ll want to rid the cylinder, crankcase, and carburetor of any old debris or gas that could hinder air and fuel flow. Clean the entire motor thoroughly, and refuel. That should get you back on the road in no time.

  7. I just installed the 2 stroke motor on my beach cruiser. When I went to start it, the rear wheel locked up and I tried engaging the clutch but it did nothing. Can you please help me figure out what to do?

    • Great question, Ethan! It sounds like your clutch is locking up. The good thing about these two stroke engines is that fixing an issue like this is pretty easy, it just takes a little bit of elbow grease.

      First you’ll want to remove the gear case cover from the motor, exposing your clutch bevel wheel and the small bevel wheel.
      Take a socket, place it over the clutch arm, and push the clutch arm in toward the motor: this is disengage it.
      Take the locking screw out of the clutch plate (next to the flower shaped nut) and loosen the flower nut. Lift the clutch plate a few cm’s and fasten the flower nut back down.
      Engage the clutch (let the clutch arm out), and watch hard close the clutch plate hits the clutch pads. If it looks like your clutch plate is squeezing down on to your clutch pads that means the clutch is still too tight. Disengage the motor, loosen the flower nut, and lift the plate a little more. The key is to make sure the clutch plate is making enough contact with the pads to grip them but not enough to squeeze down on to them. Once you’ve adjusted it to that sweet spot, just put the case cover back on and try riding again.

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