I've often wondered how I could tell if my bike was warmed up enough.  Thanks for the tip.

What is the propper method to warm up KTM XC-W/EXC/SX (2 stroke) bikes?

I ask this because I have KTM 250 EXC european model, it is exaclty as KTM 250 XC-W, After 5 min of idle, the radiators are a little bit warm, not hot, I can rest my hand on radiators way long. Some friends of mine said that should I blip the throttle few times. Is that correct?

Keep in mind that the heating up comes from combustion AND friction. The cylinder and head will hear up slower because there is not only more mass to hear than the piston but also they are the parts that are cooled (air or water). The cooling system is doing it's job by drawing heat out of the cylinder and head as soon as you start the motor. There isn't much to cool the piston besides the fresh fuel/air charge and it has less mass so it will hear up quicker. Bottom line is to wait until the cooling system comes up to temperature before flogging the motor. Usually around 170f+ or when the radiator is hot to the touch. If the bike has cooling fans they will usually kick in around 200-210f.

Also, Be careful not to boil over a bike with no overflow tank by letting it sit still for TOO long.

One final thing to consider is the engine oil will be thicker when it is cold. At very least you will be loosing some horsepower until it heats up and thins out. At worst you might have problems from lack of lubrication, but that's very uncommon...

this is very true keep in mind that this is why you dont wash your bike while the engine id hot you want the parts to cool slowly. if you cool them down by spraying it with water you could possibly cool down the cylinder and it will shrink down with the hot and expanded piston inside it. i see alot of people come off the track and start spraying there bike before it has a chance to cool down.

this is very true keep in mind that this is why you dont wash your bike while the engine id hot you want the parts to cool slowly. if you cool them down by spraying it with water you could possibly cool down the cylinder and it will shrink down with the hot and expanded piston inside it. i see a lot of people come off the track and start spraying there bike before it has a chance to cool down.

What about us off-road riders, who might go from running hot down a trail to dropping into a deep creek bed? What's the risk of damage in this scenario? I know that I've soaked my engine pretty good in the heat of battle with cold, mountain water. I've never had an issue, but that doesn't mean others have not.

What about us off-road riders, who might go from running hot down a trail to dropping into a deep creek bed? What's the risk of damage in this scenario? I know that I've soaked my engine pretty good in the heat of battle with cold, mountain water. I've never had an issue, but that doesn't mean others have not.

i would think that going from running on the track to shut down and hosing off has a greater chance of doing harm than taking a running bike through a 40* creek. if the bike keeps running it should maintain the heat and not cause any adverse issues.

Really? Dirt bike, Street bike, car, truck...Let the oil flow, let the metal heat up....Where is the mystery? IC engines of all types need lubrication and are designed to run best warm. Use good oil. Let the machine run until it sounds ready. Expect more warm-up time when it is colder. I live in the central Colorado Rockies where even summer temps can be cold, and occasionally really damned hot...Kick or switch yer bike on first, let it run at choke-off idle while you are changing into your gear, then let 'er rip!

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Good advice if I can get my neighbor to stopping and starting his bike and reving his bike that would be a great day

You didn't mention engine oil.

The engine is designed to run on oil of a particular viscosity. That "10w40" only is at the proper viscosity when it it at the correct temperature. When your engine is cold, the oil is too "thick". The result of this is that quite a bit (maybe most) of your oil is going through the oil pressure bypass valve. If you start and then just race off on a cold engine, your motor is not receiving adequate lubrication to vital internal components, such as the cam lobes, etc.

On every bike I've ever owned, dirt or street, including my aircooled '74 Yamaha RD350 2-stroke, I fire up the engine, let it idle for maybe 3 minutes while feeling the cylinders for heat. Once I feel any kind of warmth, I hit the road .. or trail. I don't go full bore to redline, or even go heavy on the throttle - I take it real easy for the first couple miles, until everything is nice and hot. The bike will always warm up faster riding it than idling - same is true for cars/trucks. I was always the only guy out of all my buddies that didn't need to rebuild or re-ring his 2-stroke after 2 straight years of severe abuse, so I must be doing something right. ?

As far as river crossings go, the same priniciple applies - crossing a 40° river with the cylinder submerged is going to lower your operating temperature a bit, but it's not going to cool down the entire engine, cases, or oil to ambient, especially when your still running. I've crossed some pretty cold rivers in winter - below freezing easily - and I've never had a failure. Lots of times I'm nearly full throttle to make it through too. Warm up, in my opinion based on years of wrenching on & rebuilding engines of all kinds, is far more important to engine life than a brief cold water contact. Out of all the people I've rode with that treated their equipment MUCH worse than I, I still have never heard of an engine failure from cold water .... at least cold water that remained outside the airbox, anyway.

Just my .02 ..

I don't think that anyone that I work with (lots of folks) warms up their car for more than 30 seconds before driving home. Is this irresponsible? There must be a lot of cars that are harmed daily if that is the case.

 I'm not saying we, or they, shouldn't warm our engines up thoroughly, just an observation.....

I've been around a while and remember something from an old Dirt Bike article that quoted Husqvarna saying that 90% of all engine wear occurs in the first 5 minutes of operation. You can imagine how this could multiply by loading the engine excessively in those first few minutes of operation.

I've been around a while and remember something from an old Dirt Bike article that quoted Husqvarna saying that 90% of all engine wear occurs in the first 5 minutes of operation. You can imagine how this could multiply by loading the engine excessively in those first few minutes of operation.

I agree with smittyman I start my bike a let it idle briefly and then ride it slowly until the engine is up to operating temperature and then let loose as a 2 stroke engine can foul the plug if allowed to idle excessively better to ride it gently 

I warm mine up for a few minutes and go never had a problem so is owing a new car that takes 0w-20w oil which is only available in synthetic bad to use when car is new for break in? 
Some say only use Dino oil for break in but that’s not possible with modern cars and  light man made only oils now I see no I’ll effects on break in with new cars using only synthetic oil…

Modern cars are sold as a “start it and go” machines. That is a big selling point and manufactures good to extreme measures to make it work. Motorcycles are racing engines and as such require more tlc.

I take the same approach with my dirt bikes as with my road vehicles.  Start the engine, let it idle for 1-3 minutes (depending on the ambient temps) and then drive it gently, no more than 1/2 throttle for the first mile or two.  After 1-2 miles it is warm enough to drive normally.  I really try to let the engine reach full temperature before giving it full beans... but of course there are rare situations where I have to push the engine hard before it's fully warm.  I've been doing this general routine for 18 years, all my engines run great and I've never once had to rebuild an engine that was bought in good condition.

On 9/5/2014 at 10:56 PM, anexcuse said:

I don't think that anyone that I work with (lots of folks) warms up their car for more than 30 seconds before driving home. Is this irresponsible? 

It depends.  If the ambient temps are very low and they drive hard after 30 seconds, yes that is irresponsible, assuming they know anything about engines and vehicles in general.  (This whole thread depends on the driver's understanding of their vehicle.)  But if the ambient temps are high and they drive gently after 30 seconds, that sounds perfectly responsible to me.  Also if the vehicle was driven within the last couple hours, there is residual heat in the engine/oil and can be treated as if the ambient temps are high.

12 hours ago, flatslide said:

I agree with smittyman I start my bike a let it idle briefly and then ride it slowly until the engine is up to operating temperature and then let loose as a 2 stroke engine can foul the plug if allowed to idle excessively better to ride it gently 

I agree with you both, for the reason that you stated.  (2-stroke GasGas EC250)

There are a few caviats to this though.

The definition of warm is quite broad as it depends on the engine.

The DRZ has huge tolerances, which is why it's indestructible and loud as hell when it runs. You're hearing the clearance between the parts. If you have a Husq, which are proper race engines in a street legal frame, the clearances are minute and wear is massive. The materials are also thinner, weaker and more exotic to get the power they want. The DRZ is a tractor and like a tractor, there isn't much wear. Even with the uneven heating of parts, the wear isn't that big, as the piston rings take up the difference. Only when you lose all coolant you're in trouble, as the aluminum piston grows much faster and much more relative to the cylinder wall, the rings will close up and scrape the walls. 

Older engines need a lot more time to warm up, because they're not as well designed in modern terms. Old school materials that take forever to heat up, high clearance but also poor precision so wear is still high. Thick oil that needs to warm up and get circulated, etc. These engines need to be warmed up very well before using.

Modern engines run super thin oil, so it is ready to go right away, with modern precision doing most of the work. Both cars and most motorbikes. 

Formula 1 engines need hot oil and hot coolant pumped through them before they can be started as they're completely seized when cold. It cannot move, that's how tight everything is.

The DRZ has the added advantage of being dry sump, so there's very little oil in the engine, so it heats up fast. The paper filter is also coarse enough to flow cold oil in the right viscosity. 

The coolant first runs in a closed loop around the cylinder, controlled by the thermostat, so it only needs to warm up a fraction of the coolant. Once the radiators get slightly warm, the engine itself is ready, as it opens the thermostat to get rid of excess heat. The fan comes on when it's at around 90C/194F, which should be just after the thermostat opens.

An engine like the DRZ has no problems with starting, idle for 30 seconds to build oil pressure and the riding it gently for the first few minutes, as theres enough clearance when it's cold.

Letting it idle takes forever as it only has a small amount of fuel creating little heat, hence people rev it to get bigger explosions and more heat, without moving the transmission and putting a lot pressure on the bearings. Also revs up the oil pump, creating more pressure which heats the oil and forces it through the system. Riding it does a better job though, as long as you don't flog it, because you create the most heat without much strain on the engine. 

The big end is roller bearings, there's ball bearings in the engine cases, so as long as you don't put a ton of pressure through the gearbox, you're fine in terms of wear. Plain bearings are a different matter, especially in older engines. Mine ran without oil, didn't notice until it started seizing during a long highway trip. Only killed the big end, cylinder was still fine. Turned out the previous owner didn't install the oil jet going to the head, so it pumped all the oil out in that long ride. 

Very, very long story short, it depends on the engine. Idling it is not very efficient to warm it up, regular bikes are designed to be ridden not raced, so don't need race level warmup. How modern the engine is makes all the difference, as does using the right oil.