mdkuni
TY 4 Stroke Guru
I am looking for some explanation on the importance of engine warm up. I have always believed in allowing an engine sufficient time to warm up before cranking on it. I probably allow more time then what is needed but I am very cautious about these things. I guess I have never had a real mechanical explanation as to why this is important though. Can anyone explain this, and is there a difference in importance when comparing a 4-stroke to a 2-stroke?
craze1cars
VIP Member
There's really three aspects I can think of to a warmup...one is that all the different sizes/types/shapes of metal in an engine will expand at different rates as temperature changes. This is largely a 2 stroke issue, but can affect 4 strokes also.
Two is that oil doesn't flow or lubricate well when it's thick due to being very cold (more important at below freezing temps, especially sub-zero F). This is primarily a 4 stroke issue.
Three is that moving air is colder than still air, and the faster it moves, the colder it gets...this is not an engine problem per-se but it can cause carburator freeze-up which could lead to a lean burndown on many carb'd snowmobiles. In my experience this was VERY common on 90's Ski-Doos. Fire them up on a -20F morning, rev them just a bit too quickly early on (about 2,200 rpm was all it took on my 670), and suddenly that gulp of cold air condenses a thick buildup of frost in various air and/or fuel passages and you air/fuel mixture is so far off (maybe rich, maybe lean...depends on what passage is clogged or partially constricted) it might not even run at all. 15 minutes with a heat gun (I kept one in my trailer with a LONG extension cord for just such an occurrance) or if you're lucky drag it into a heated garage for 1/2 hour or so until the frost melts. Suddenly all is well again. You'll note that later model Doos all have heated carbs to help prevent this (they run engine coolant through the carbs to heat the metal). Likely other brands are similar but I'm less familiar with them.
Engine-wise, two strokes are susceptible to classic "cold seizure", where the piston gets hot and expands faster than the cylinder itself. This is caused by revving to hard and fast with a cold engine. Suddenly the piston/rings expand to the point that they simply don't fit anymore and you have a "four point seizure". 4 strokes are less known for this, but it could theoretically happen. On 4 strokes a bigger issue, IMO, is that their oil is thick as molasses in extreme cold and needs a little time to warm so it flows better to lubricate properly. Synthetics help this a lot, but they can get thick in extreme cold, too.
My opinion, for most any sled, 2 or 4 stroke on extremely cold days....fire it up and simply let it idle without any revving until you can feel a little bit of heat coming through the first heat exchanger...just pull your glove off and touch it. If it feels like ice you're not ready yet, but if it's getting a little warm this means the engine has heated enough to open the thermostat once or twice, and the engine internals have basically reached normal operating temp. This gives plenty of time for oil to heat and thin out, and no sudden expansion of critical components.
On warmer days (20F and up), I feel this is less important. Fire it up, idle for maybe 2 minutes, and then ride it slowly and gently for the first few miles. Then let 'er rip.
Two is that oil doesn't flow or lubricate well when it's thick due to being very cold (more important at below freezing temps, especially sub-zero F). This is primarily a 4 stroke issue.
Three is that moving air is colder than still air, and the faster it moves, the colder it gets...this is not an engine problem per-se but it can cause carburator freeze-up which could lead to a lean burndown on many carb'd snowmobiles. In my experience this was VERY common on 90's Ski-Doos. Fire them up on a -20F morning, rev them just a bit too quickly early on (about 2,200 rpm was all it took on my 670), and suddenly that gulp of cold air condenses a thick buildup of frost in various air and/or fuel passages and you air/fuel mixture is so far off (maybe rich, maybe lean...depends on what passage is clogged or partially constricted) it might not even run at all. 15 minutes with a heat gun (I kept one in my trailer with a LONG extension cord for just such an occurrance) or if you're lucky drag it into a heated garage for 1/2 hour or so until the frost melts. Suddenly all is well again. You'll note that later model Doos all have heated carbs to help prevent this (they run engine coolant through the carbs to heat the metal). Likely other brands are similar but I'm less familiar with them.
Engine-wise, two strokes are susceptible to classic "cold seizure", where the piston gets hot and expands faster than the cylinder itself. This is caused by revving to hard and fast with a cold engine. Suddenly the piston/rings expand to the point that they simply don't fit anymore and you have a "four point seizure". 4 strokes are less known for this, but it could theoretically happen. On 4 strokes a bigger issue, IMO, is that their oil is thick as molasses in extreme cold and needs a little time to warm so it flows better to lubricate properly. Synthetics help this a lot, but they can get thick in extreme cold, too.
My opinion, for most any sled, 2 or 4 stroke on extremely cold days....fire it up and simply let it idle without any revving until you can feel a little bit of heat coming through the first heat exchanger...just pull your glove off and touch it. If it feels like ice you're not ready yet, but if it's getting a little warm this means the engine has heated enough to open the thermostat once or twice, and the engine internals have basically reached normal operating temp. This gives plenty of time for oil to heat and thin out, and no sudden expansion of critical components.
On warmer days (20F and up), I feel this is less important. Fire it up, idle for maybe 2 minutes, and then ride it slowly and gently for the first few miles. Then let 'er rip.
Mighty
TY 4 Stroke God
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Yeah, what he said ^
But to simplify it some it's pretty simple. First off, Yamaha built in a safe guard and won't allow you to hammer it until the engine reaches sufficient temp. on our 4-strokes. 2-strokes are the real problem in this arena, the pistons heat up so much quicker than the cylinders and expand which can cause you to stick a piston if you don't warm them up before juicing them.
But to simplify it some it's pretty simple. First off, Yamaha built in a safe guard and won't allow you to hammer it until the engine reaches sufficient temp. on our 4-strokes. 2-strokes are the real problem in this arena, the pistons heat up so much quicker than the cylinders and expand which can cause you to stick a piston if you don't warm them up before juicing them.
That is a very good run down c1c.
Also, the type of cooling system makes a big difference. An air or fan cooled engine takes a lot less time to reach operating temps than a liquid cooled does. I know there aren't too many guys running air or fan cooled sleds out there anymore but I though I would point it out.
The big thing is to do as craze1cars says at the end take it easy and don't rev it hard for the first few miles. It is not that you cannot touch the throttle at all if it is cold just don't go reving it right away.
Start it and let it warm up until the heat exchangers are warm and then ride at a nice steady slow to mid speed to really get things flowing. Then once you can tell that things are working freely.........let 'r rip!!!!
Also, the type of cooling system makes a big difference. An air or fan cooled engine takes a lot less time to reach operating temps than a liquid cooled does. I know there aren't too many guys running air or fan cooled sleds out there anymore but I though I would point it out.
The big thing is to do as craze1cars says at the end take it easy and don't rev it hard for the first few miles. It is not that you cannot touch the throttle at all if it is cold just don't go reving it right away.
Start it and let it warm up until the heat exchangers are warm and then ride at a nice steady slow to mid speed to really get things flowing. Then once you can tell that things are working freely.........let 'r rip!!!!
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what was described is basiclyy what i did with my sx500r. i do the same with my warrior. its hard to go slow though. i live on a lake that the groomed trail crosses so its very tempting to rip it right away going across the lake. i tend to hold it to 50kph till i hit the trail 1/2km away. once i hit the trail she is all warmed up and i let'er rip. the sxr runs cloder than most though because i put a srx rear cooler in it on its 2nd season because i was roastin my feet the 1st season i had the sled.
LuvMyWarrior
Extreme
Think of it this way: When you first wake up in the morning do you jump out of bed full speed and run the Chicago Marathon? Of course not - takes you a while to get going. Engines are no different.
BlgsRX-1mtn
TY 4 Stroke God
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I generally start both sleds and let them idle while I remove the anchors for the skis, remove the fuel cans up front, drop the salt guard/drive off ramps, put the covers in the tow vehicle and get all my riding gear laid out to put on.
This generally gives both; the 4-stroke and wife's 2-stroke plenty of time to warm up. I'll then take a quick rip across the parking lot to clear the cylinders out then shut them off. Finally, it's time to throw the baggage on the sleds check oil levels, gear up and hit the trail.
Jim
This generally gives both; the 4-stroke and wife's 2-stroke plenty of time to warm up. I'll then take a quick rip across the parking lot to clear the cylinders out then shut them off. Finally, it's time to throw the baggage on the sleds check oil levels, gear up and hit the trail.
Jim
I think with our new 4-strokes it will be easier to just let them sit and warm-up. While my SXr 700 was setup to idle and not load-up, it would still spew a cloud of smoke, and most of the 2-strokes in our group need attention when idling cold to either keep them running or not foul a plug. The 4-strokes could sit by themselves while we finish getting dressed, and there won't be a cloud of smoke in the driveway.
Mighty is right, anytime the cold engine light is on in the gauge, the rev limiter is lowered, and the colder the engine is, the lower the rev limit.
The Yam engineers built it in to prevent someone from starting a cold sled and hammering it wide open.
The Yam engineers built it in to prevent someone from starting a cold sled and hammering it wide open.
mdkuni
TY 4 Stroke Guru
Do all of you feel the engine temp light on the four strokes is sufficient time for a warm up or should you allow some slower warm up speeds before getting on it. I always wait a good 5 minutes or so after the light is off before I even think of getting on it all the way... In my opinion it is a whole lot of RPM's at WOT to be running an engine that is not at proper temp.
stumper
Extreme
A nice gradual warm-up for a mile or so is nice as it gives the whole driveline a chance to warm up together. As tough as it is to wait before honkin' on it, it pays dividends in a longer engine life as well as less repairs in the long run. **The preceding message comes from my"IMHO" and "common sense/seat of the pants" files** . A sled that idles for 5 minutes has a warm motor that gets loaded by a cold drivetrain.
rx1mtn
Expert
Don't forget to warm up the chain case and other drive line bearings. I NEVER just take off down the trail at speed. I go about 10 to 15 mph for the 1st mile or so, just so the chain case an other bearings can get the lube going.
I've seen three of my buddies let their engines warm up, pull right down onto the lake, let 'em rip, and proceed to blow belts because they were still cold.
maddogjeff
Expert
Look at this way, if you jam your piston into a cold cylinder there's a good chance of breaking it. You really need to warm her up and get the lubrication going so the piston moves in that cylinder without any friction. It's a law of nature and thermodynamics. javascript:emoticon('
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attakred06
Pro
hi guys i fix this at first sight ! the first week i own my attak i install a remote start;alarm 2 ways system IT START BEFORE I GET DRESS AND NO ONES COME CLOSE TO IT I ALSO PUT A SENSOR IN THE TRUNK!!!!! the yam can also start by itself every 2 hours for thoses cold wood nights... i test it at -38celcius last winter. was real good so bye!!!!!
