Ya know what grinds my gears? Impatient 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 engine blew…
There IS a right and wrong way to start and warm-up your dirt bike, and it isn’t any harder to do it correctly. This article will show you how to properly warm up your engine, whether it’s a 2 or 4 stroke, liquid cooled or air cooled.
How To Warm Up A 2-Stroke Dirt Bike
2-stroke 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 your dirt bike running right (or at all).
How to destroy your engine
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!……..
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.
All metals expand at least to some degree as they hear up. If a part 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 happen sooner rather than later.
As a result, your bike will be out of commission, and your wallet will be one or three sizes smaller after you repair.
Do THIS, or your dirt bike will break…
Now, the correct way to start a cold 2 stroke 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 shouldn’t rev the bike much, if at all.
How long does it need to idle for?
Depending what the air temperature is, you should let your dirt bike idle for 1-3 minutes. During this time, I 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!
How To Warm Up A 4-Stroke Dirt Bike
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.
How long to use choke and idle?
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 too 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.
If you have a liquid-cooled 4 stroke dirt bike, such as a motocross or enduro bike, letting it idle too long is the most common reason for the head pipe glowing red. The radiators need air to cool them down. The engine is not built to withstand idling for long periods of time before overheating.
How do you treat your possessions?
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.
Now that we’ve covered how to warm up your bike, it’s time to learn how to properly ride it. You could learn on your own and make mistakes, or you could start out on the easy path and learn from my mistakes.
To become a good dirt biker rider, you must master the basic skills of throttle, clutch, and balance control. Having a properly setup dirt bike to fit YOUR personal needs is another piece to the puzzle.
Want to become a better rider by taking just a few minutes to read all the basics? Click here to learn proper riding technique for better control.
Thursday 27th of April 2023
gas and oil don't separate after mixing...
high output water cooled two strokes should be warmed up following the factory recommendations (like aprilia/ suzuki/ yamaha) for their race bikes--which is basically the OPPOSITE of what you suggest- here's the suzuki description- the engine should be revved repeatedly to 60% of redline for two minutes, then 80% of redline until its fully warmed up..
idling or low speed warm-up is exactly the way to cause cold seizure when it's operated under load... even though the water temp will be hot enough to open the thermostat, the cylinder and piston will not be at normal operating temps with the revving-- check any factory literature on two stroke track bikes (road racing)
Friday 28th of April 2023
Hey Peterman, thanks for your comment. That's very interesting. I'll have to look into it some more, but based on my years of owning many different 2 strokes and what the OEM manuals say, I've never had a problem doing what I recommend in this article. On the flip side, I have known other people that have cold seized engines and they warm up a 2 stroke as you recommend. As for oil separating, I've only ever had a problem with premix once and that was with 2 stroke castor oil - it's harder to stay mixed with gas, especially in colder temps (which it was that day). The Yamaha YZ125 manual says this for starting a cold engine: "Run the engine at idle or slightly higher until it warms up: this usually takes about one or two minutes. The engine is warmed up when it responds normally to the throttle with the choke turned off."
Thursday 29th of August 2019
I hear all the time that two strokes can rev really high. I have a 1982 Suzuki TRS with open cone filter and an aftermarket exhaust. What can these older bike rev all day at? Btw stock piston and rings
Monday 10th of September 2018
I know this is several years after your post, but I want to thank you for it. I'm sure I've been guilty a number of times of not properly warming up bikes when I've gone riding, although I'm not a WOT rider, so thankfully I won't have done the worst possible to them. But, I've just bought some used bikes after not riding for about 15 years, so I'm doing a lot of reading - might as well make sure I do things right, and make them last!
Friday 9th of May 2014
I have a 98 yz125 and when I first start the bike it idles pretty high but when its warmed up it wont idle it just dies. Is this something to do with my jetting or is it normal?
Saturday 22nd of March 2014
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
Tuesday 25th of March 2014
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?