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-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!……..
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.
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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!
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.