Troubleshooting your engine
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 into your motor
Checking fuel flow on your engine
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 into 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 into 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
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.
Displaying fuel valve in both open and closed positions
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
Checking clutch handle
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
Checking 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
Inside of bevel wheel
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



I have a 80cc 2 stroke and i just installed it. Went to start it and i got nothing. It has spark and it has fuel going into the engine the compression is good and i am completely stumped ive even been towed and it wont start. It doesmt even want to fire up. If theres something im doing wrong please tell me thanks


Hello bike berry I just bought a two stroke engine I have everything running and it is the best thing ever!!!


My bike was riding fine and all of a sudden it wouldn’t start at first I thought a lemon but the rep told me what to do and then I started researching and found this and it was helpful exactly what the rep was telling me to do.


My bike will start but dies when i pull in the clutch and has very little power throttle does nothing but reed valves and carb is loose could that be the problem? not enough compression


My husband wanted me to let you know that this is awesome and that it helped him.


Hey there, I have a 80cc engine that I just put together and the the chain is stuck and won’t let me pedal. I am sure it is not the bike chain. What do you think is the problem?


i tried starting my 2stroke today and when i pull the cluch and let go the back tire just stops theres no leaks everything is tight cluch cabel is fine not to loose not to tight.i was just riding it two days ago and then i did that clutch adjustment and it worked for me so now i know that these sometimes need to be adjusted right out the box


Hi I have a 66/80 cc I could not get it to run for the life of me i then called in bikeberry and they directed me to this blog now i can get it going!!


The brass piece came loose in my carb and was at bottom of bowl. Screwed it back on and now the bike starts.


I just installed brand new 80cc kit and at first went to start it i had trouble but now i think i know what to do.


Hi love my flying horse motor fly’s! HP carb head and banana muffler.


I bought a motorised bike off my friend and he told me that the clutch handle itself was broken and just needed to be changed, otherwise the bike was in working order. He hadn’t rode the bike in maybe 1-2 months and after I fixed the clutch handle it was ready to go. These bikes are very easy to maintain and work on.


Cool got this saved for any issues.

joe easler

I’m also looking to purchase the predator 212 motor kit for another project. Is there any install instructions.


Hello my 80cc motor ran for about 10 min after I installed it. Then bogged out and won’t start again. I came came across this article about the same issue i was having and i went through it a few times and finally it helped me out there.

johnny bonacci

First off i would like to let you know that i do not own a bike with a motor. A couple of friends around my area do. And they all get the parts from BikeBerry. I am a motorcycle and jet-ski mechanic with 20 years in the trade. I have built a few of the bike motors around here. I have also bought parts from your place to fix motorcycles that i have worked on in my garage. Your prices are great, plus you guys are about 1 mile from my home so that makes it very practical. Anyway, the reason for my post is to compliment your technical advice for the people who needed some help with their motors. You provided solid advice and made it understandable for the people who might not understand what your trying to explain. So again>>>>>great job, and keep up the great service you guys are providing.


“Hi I am new to all of this motorized bikes. I have been having issues from the start but seriously after reading your blogs and going through these steps it helped me and i was able to diagnose the issue. It is awesome to have came across this and thank you for providing this information great website too.”


So brand new engine, got it mounted and properly wired and i am ready to go thanks!


“Hi, great work thank you for helping me. "


Hello, I was not able to start my engine before reading this, after going through each step i learned that i had a faulty electrical coil i got that replaced and now i am good to go thanks broo..


Hi, I just got my 2 stroke bike kit today and it works great.!!!


so i bought a 66cc/80cc motor kit, did 8oz to 1gal first 2 tanks. went down to 6oz to 1 gal thanks for that informatton i didnt receive a DVD so i was a little confused.


Got a 2stroke that ran when I first got it then it stopped running. I checked off what you told me to do and it came down to a bad CDI bikeberry replaced it and now there is no stopping me LOL!!


No spark pretty sure coil bad what should magneto output read on meter and can u use coil from a dirt bike


I saw your earlier comment to someone who’s having the same problem just now my spark plug is completely dry I poured some fuel into the spark plug chamber and it did fire up thank you so much man!!!


Went through your steps because boy was i having trouble but this worked cool beans.


I was able to take these steps and use them on my sons bike and they worked. Thank you BikeBerry for helping a mama!


this is exactly what i needed to do i had to adjust the clutch, thanks yall.


“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."


“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.”


“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 <a href="""" rel=""nofollow"">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."


“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.”


“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."


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?

Kevin king

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

Vawn Davis



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?


My bike wants to start.then quits.I know I have to get a spark plug but that’s all I know.thank you


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.

Mitchell miller

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.


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.


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.

Mike davis

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.


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 Ricky,

We have the CDI Electron Ignition Coil and Magneto Loop Set Replacement Set for $24.95. If you have any further questions please feel free to let us know.

Best Regards,


Where do I buy a Magneto and a CDI coil and how much do they cost because I thought it was a spark plug brought one at auto zone still nothing



We do understand, this issue can be coming from the pedal clearance on the bike to clear that way through. For the best results with this issue, you would need the Wide Crank Assembly this will give you the clearance needed and give you the better push.

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