How To Warm Up A Dirt Bike – The Right Way

Ya know what grinds my gears? Ignorant riders that do not know how to warm up dirt bike the right way. I hate to see a bike go to waste when it could have easily been avoided, and then the owner wonders why their top-end blew… There IS a right and wrong way to start your dirt bike, and it isn’t any harder to do it correctly.

2-Strokes

2-cycle motocross bikes are high-performance race-machines, and should be treated as such. This is not to say that they aren’t reliable, because they often are if you take care of them. Doing routine maintenance and proper warm-up procedures are a must to keep these running right (or at all).

The wrong way to warm up a 2-stroke (which I see way too often): Starting up the bike with a cold engine, and once it’s running, repeatedly holding the throttle open for a number of seconds until it’s relatively warm. After the rider revs it out until it won’t “cough” and smoke any more, he/she puts it in gear and goes WOT!……..

Umm......... yeah.

First of all, it sickens me to see people (even ones that take decent care of their bikes) do this to their precious machine. What they probably don’t realize is that the piston needs to warm up and “expand” to the size of the cylinder bore. If it expands too quickly (by revving the snot out of it on first start up) it could cause a cold-seized engine, whether it be a crank bearing or the piston. This may not happen the first time, but if done over and over, it will. As a result, your bike will be out of commission, and your wallet will be one or three sizes smaller.

Do THIS, or Your Bike Will Break…

Now the correct way to start a cold engine that will make it last much longer, is as follows… Before you even turn the gas petcock to “On”, shake the gas tank around so that the 2-stroke oil and gas are mixed properly. Now turn the gas and choke on (depending on air temperature). Turn the engine over a few times to make sure it has enough lubrication. Without touching or giving it much throttle, give it a good kick to start it up. Leave the choke on for 30-60 seconds after starting it up. During this time you should NOT touch the throttle; let the bike warm up by itself.

Depending what the air temperature is, you should let your dirt bike idle for 1-3 minutes. After this time, give the throttle a little flick, and it if still bogs or hick-ups then it’s not warm yet. If it revs like normal, then it’s time to put it in gear. Although, it’s still NOT time to go WOT (wide-open-throttle). The bike won’t be up to full operating temps, so you have to click down into first and putt around on it. This should be done by going up to about 1/2 throttle for another couple minutes (possibly longer if your bike continues to hesitate upon acceleration). After cruising around for X amount of time until it’s hot, THEN it is time to let ‘er buck!

4-Strokes

On the flip side, 4-stroke motocross bikes do not require as much warm-up time as a 2-stroke does. This is because four-stroke engines run at higher temps, and if they aren’t getting enough air-flow they will over-heat (more on this in a future article).

Now do as you would a 2-stroke; turning the gas and choke on, give it a couple squirts of gas to prime it (luckily you don’t have gas to mix). Now start the bike, but don’t touch the throttle when kicking or it may kick back and leave you with a bruise (if you need help on actually starting your dirt bike, check out our vid on How To Start A Dirt Bike). Once your bike is running and idling smoothly, you can flip the choke off. Now, you only have to let it idle for about 30 seconds to a minute; any more than that for a 4-stroke motocross bike and it will start to get hot. If you want to stay on the safe side, you can cruise around on it for another minute or two, but after that you will want to get it breathing.

It really ticks me off when someone doesn’t let their motocross bike warm up before riding it like it’s stolen. Although it’s their dirt bike and they paid for it (hopefully) and can do what they want with it, I hope you are smarter than that. Do your bike (and wallet) a favor, and take the extra couple minutes to let your high-buck motocross bike properly warm up.

-Tom Stark

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31 Comments

  • [...] Properly Warming Up Your Dirt Bike is part of it, which is why I never let my four-strokes idle for very long when I first start them up. How do I know this, you ask? Well, I know of many people that have burnt valves more often than usual, and it wasn’t coincidence. No, it was because they putt around on their bikes. [...]

  • j bee says:

    I am a new dirtbike rider with an 04 KX 125. I’ve been reading a lot about an idle not being a good thing due to plug fouling on the 2 strokes. Your article is good but can you comment on this? Also, should you end with a hard ride and then shut down or give it a few mins of idle then off? Thanks.

  • Tom Stark says:

    Every bike can idle, and should be able to idle without fouling a spark plug. 4-strokes just idle more smoothly. If it’s fouling plugs at idle, then your pilot jet is probably rich. It’s okay to shut it off right away, but you should wait for it to cool down a little bit before spraying it down with water.

  • carl H says:

    hello guys I am buying a bike in the next 2 weeks been stewing over n over about 2/4strokes.

    iv had 2 strokes in the past and fast n confident on them o4 was me last model.

    what do ya think ? i was keen on tryingthe 4stroke but like ppl say its a lot of money on maintenanct isit? I’m thinking aroung the 08 model now.

  • Tom Stark says:

    It really depends on the rider. I enjoy 2-strokes more because they’re more fun to ride, but I’ve had my share of 4-strokes as well. As long as you do the proper maintenance, a 4-stroke can last just as long (it will probably be more in the long run though). If you’re on a budget, I’d go 2-stroke. They’re easy to maintain and rebuild, and the power delivery makes them a blast to ride!

  • barn95 says:

    I have a little 70cc lifan. i got it a littke while ago just to mess around with. im 16 and it is the first dirtbike ive ever had. its getting cold out but i still want to go out on it and tear it up. but a guy that lives next to me said that of i try starting it on the cold and just ley it idle for a minute..that i could blow it up bc the oil wont be “thin” enough to get in and around the motor. i dont know if he is right or not. please reply.

  • Tom Stark says:

    How cold are we talking here? If it’s above zero degrees Fahrenheit then regular 5w-30 or 10w-40 works fine.

  • Vic says:

    I’m a beginner at riding and I’m 38. Really lookin for any tips to help me maintain my kx125 I got for Christmas. I take care of all my toys and I need tips in this. Any tips will help me out. Thanx

  • Tom Stark says:

    Hey Vic, what an awesome gift to receive (I hope you thanked them)! The main things are regularly changing the oil and cleaning the air filter every 5 hours or so. If you ride in sandy or muddy conditions you’ll want to clean the filter every ride. Keep the chain lubed, check and make sure all the nuts/bolts are torqued down properly. Buy some spare spark plugs if you haven’t already. Jetting is key, so head on over to my “Jetting 101″ article for some tips. Always warm the bike up properly and it will last you a while. It’s a good idea to put in a new piston and/or ring every season, depending on how often you ride. Good luck!

  • Vic says:

    It’s Vic again. Question: is it ok to have the idle set on low or almost shutting off or have it at a descent idle.

  • Tom Stark says:

    That’s up to you. If you are racing motocross then it doesn’t make much difference. For trail riding you don’t want it to die, so you might want to bump it up a little. To set the idle, warm the bike up first, and then adjust the idle screw until you get it where you want it.

  • Vic says:

    Would a k&n air filter be the best air filter for me to get for my kx125?

  • Tom Stark says:

    Pretty much any name brand filter will be fine. It’s more important that you keep it clean than what brand you use.

  • [...] temporarily fix this, assuming the bike is fully warmed up, give it a few quick bursts of WOT (Wide-open-throttle). This will clear it out, and should run [...]

  • Marcus says:

    Hey Tom,

    I bought a kx 80 kawasaki 2-stroke(late 1990s model) from a friend, last october. I was riding regularly up until about late november. Then I got real busy and it also got real cold. The last time it was rode it was like Dec 1st. I tried to start it up yesterday for about 20 mins using the kickstart and trying to run start it(run with it, then hop on and kick it into gear.) My friend does it and it works fine, I’m not sure if it’s a good way to start it or not. I could never get it to start and I want to know what I should do? I’m going to take a trip to a dirt bike place and ask them the same question, but I thought I would ask you too.

    Changed the spark plug in November, what else might need to be changed if anything?

  • Tom Stark says:

    Are you referring to Bump Starting your dirt bike? Have you checked the compression? Is the air filter clean? There’s a good chance your carburetor is dirty. Get it cleaned and put some fresh premix in.

  • Marcus says:

    Yes I meant bump start, I was doing that wrong. But, I am new to dirt bikes so I don’t know how to check compression, clean the air filter, or clean the carburetor. So can you explain? And, do I have to put all new gas in there or can I just put a little more gas in the tank since it is not all the way full?

  • Marcus says:

    Update…

    I let the gas drain out. I am changing the air filter now. I am also going to put another spring in the kickstart because it is getting stuck when I kick down sometimes. If these things do not work than I will check the compression and clean the carburetor.

  • Marcus says:

    My kickstart is getting stuck when I kick down. Do you think it is the spring or what? I have not taken anything apart yet, I want to make sure I am doing it right and I am taking the right steps before I just jump into it.

  • Tom Stark says:

    So the kick-starter won’t move at all? If that’s the case, then your engine is more than likely seized, unfortunately. Pull apart the top-end and see what damage has been done.

  • Marcus says:

    No it moves when I kick down, but sometimes it get stuck in the down position and I have to pull it up with my hand. I went to the dirt bike place the other day, and he told me that it is probably the kick starter spring. I am going to take it off today, but I just wanted a second opinion.

  • Tom Stark says:

    Yeah, that definitely sounds like the spring. Replace it and see what happens.

  • Evan says:

    Hi i warm up my bike and then rip around for like a minute then it just bogs out and the exhaust putters and wont start for like another few hours…does anyone no whats happening or the problem…thanks

  • Peter says:

    Hi,
    First of all, I enjoy reading your articles as they are very helpful.
    I recently bought a 2001 KTM 125 sx. I am concerned about its power though. the engine over-revs quickly and loudly. however there is no power compared with the engine’s sound. My friend told me something about compression, but will I solve the problem by buying a new piston ? Another thing is that when I pull into the clutch, there will be maybe 4 seconds delay for the engine to idle.
    Thanks in advance !

  • Tom Stark says:

    Glad to hear you enjoy Motocross Hideout! How long have you had the bike, and has it always done this? If you don’t already, get a manual for your bike, especially if you don’t have much experience working on it. It’s hard to tell what your problem is over text, but I would check the clutch and fluid first. Make sure it’s properly bled, and the plates/disks/basket are in good shape. There’s a chance the clutch is slipping because it’s old/worn out. Otherwise your bike may just be low on compression and needs a new top-end. I’d recommend getting a friend that knows what they are doing to help. Let me know how it goes!

  • [...] and make sure everything feels right, like it’s disengaging and engaging. On the first start, warm the bike up properly¬†by letting it idle for at least a couple minutes. It’s not unusual for the clutch to drag at [...]

  • Mark says:

    You don’t know what you’re talking about!. U warm up the engine until the cylinder is warm/hot to the touch!. And 2 strokes don’t like to run at idle rpm as the porting is designed for higher rpm. The fuel doesn’t atomize well and it just ends up pooling in the sump and fouling the plug. I really wish i had made a youtube video when i still had my bike, to show people how to operate an engine when its cold ONCE AND FOR ALL!!

  • Tom Stark says:

    So you are saying you’re supposed to start it up and keep it at high RPM until it’s warm? I’ve had plenty of 2-strokes, and if they’re properly jetted, they won’t foul a plug after idling for a couple minutes of warm-up.

  • Mark says:

    Of course not!. What im saying is… u don’t just let it sit idling until the engine gets hot. U get the rpm up just above idle (around 1/8 throttle) until the cylinder is quite warm to the touch. Then u can start revving it to clear it out and get it fully warmed up.

  • steve says:

    Tom, I am new to this. I have a 2003 flywing100. It feels like the gears are not catching I don’t know it just seems like its not as fast as it used to be either. What can I do. Also hard as shit to start. I have to start with choke on and as soon as it runs I have to open it and rev for a while. 4stroke, 4speeds

  • Tom Stark says:

    Sounds like the clutch may be slipping. Have you tried adjusting the cable? How much free play does it have? What color is the spark plug?

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