oil tank vs. oil cooler.

12 replies to this topic
  • tool

Posted November 04, 2004 - 01:44 PM


with yamaha (hopefully) putting the aluminum frame on the thumpers next year, i was thinking...

why have an oil tank in the frame, when you could have an oil cooler as the oil tank? maybe i dont know the specifics (like capacity, placement, etc.), but the current oil-in-the-frame setup seems like it would insulate the oil temp. why does that make sense?
maybe just a smallish cooler in front of one of the radiators, then the coolant would take the heat from the oil and disperse it. :cry: this would have to reduce the overall temp of the engine.

the way i see it:
oil tank - keeps the oil hot, but cant be smashed in a crash.
oil cooler - cools the oil, but could get smashed and leak.

if the only disadvantage is the cooler being smashed, why not just put a gaurd on it? they are on those high dollar xr50's, why arent they on the bigger, hotter 4 strokes?

  • demonicracing

Posted November 04, 2004 - 02:11 PM


I think you answered your own question- most oil coolers don't hold much oil volume at all, only a cup or two. So you would still need to have a tank and cooler. Plus, oil coolers are very fragile and would add cost and unnecessary complexity and leaking potential. If the motor runs fine without the need for the cooler, why add one?

  • tool

Posted November 04, 2004 - 02:38 PM


If the motor runs fine without the need for the cooler, why add one?

well, the cooling seems necessary when a 4 stroke can boil over in 3 minutes. maybe if the oil wasnt so hot to begin with, there would be less heat build up that the cooling system would have to get rid of. also, wouldnt the oil last longer with less heat?
i saw something about it in MXA, they said the factory teams are tesing oil coolers on thier "highly stressed" 250f race bikes.
but i see your point, there would be reliability issues. and it wouldnt make the bike any lighter either. :cry: it just seems logical, the coolant cools the head, but theres nothing that directly reduces the heat in the bottom end.

  • YZ250F_Rider

Posted November 04, 2004 - 04:36 PM


The whole frame will act as the oil cooler. Just as it does now. It will allow heat to soak into the aluminum faster than steel does so there will be a beneficial increase in heat capacity.

If you want the bike to stay cool then consider changing the guards for the radiators. Most woods riding guards cool better than the factory plastic ones because they let the air flow straight into the radiator.

  • grayracer513

Posted November 04, 2004 - 10:21 PM


well, the cooling seems necessary when a 4 stroke can boil over in 3 minutes. maybe if the oil wasnt so hot to begin with, there would be less heat build up that the cooling system would have to get rid of. also, wouldnt the oil last longer with less heat?

The oil is not the cooling media in the engine. The only purpose for an oil cooler is to keep the oil temp below a desired level. Coolers were being used in addition to, not as a substitute for, the tank. The engine oil is not the source of heat, either, it's a victim of it. the cooling system doesn't really do much to lower oil temperatures except in a very indirect way.

One of the biggest reasons 4 strokes heat up so fast at a standstill can be seen by looking at the inside of the head. Show me where the coolant touches the combustion chamber. The only thing in there is 5 valves! Most of the heat is drawn off from the top half inch of the cylinder and from around the exhaust ports as they pass through the coolant in the head. Circulating the coolant is very important. Compare this with a two stroke's combustion chamber. It's surrounded with so much water that it can idle until it has a crankcase full of black drool and still not boil.

  • tool

Posted November 05, 2004 - 04:07 AM


it just seems annoying to me when im trail riding, everytime we stop i have to shut the engine off, since it is ready to boil over.
theres got to be something to reduce this heat.
im using woods rad gaurds and the overflow tank and engine ice. i guess the key here is circulating the coolant. but after i raised the compression, there is more heat. the oil is totally trashed in 2 relatively short rides. i mean its kind of black, but it looks more grey than anything. like there lots of metalic sludge in it.
i guess the last thing i can do is get a boyesen water pump, if that doesnt help cool the thumper down, nothing will.

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  • YZ250F_Rider

Posted November 05, 2004 - 04:41 AM


the rads are just barely enough to handle the heat output of the stock engine. Increasing the compression put them over their capacity.

Try running pure distilled water and some water wtter instead of engine ice. It has ~30% more heat capacity and will help. You can also look into hanging some larger rads on it as well.

  • ncmountainman

Posted November 05, 2004 - 07:09 AM


i feel your pain mr. tool,i've been on a quest to make this thing run cooler myself! lots of tight woods riding + the rekluse = heat the boyesen pump helped alot,and i run a 50/50 mix of water wetter and engine ice(it gives you the protection from freezing) although not as effective as WW and water it is still way better than straight engine ice. since removal of my overflow tank i've went to a 1.6 kg rad. cap off an kx 500(and no its not blowin hoses it was 85 deg sunday on tight sing track) i've also tried this stuff called two2cool oil additive,it is friction modifier free and safe for wet clutchs.i was skeptical at first but after talking to several people that swear by it i gave it a try. well it works! i could not rest my hand on my clutch cover for more than 1 sec before and now i can hold it there for a 3 count! now all you skeptics who are gonna talk about heat transfer and it must go somewhere,this stuff allows the oil to bond to the hottest areas of your engine thereby reducing friction/heat. it was explained like when you pour oil into a hot skillet it wants to repel,well this reverses that action so that oil is drawn to the heat. well whatever it does it works i've never seen my oil come out so clean! :cry: there is an in depth thread talking with the manufacturer a ways back on the xr250 forum :cry:

  • tool

Posted November 05, 2004 - 10:08 AM


its the mountain man with the knowledge. :cry:
i wasnt aware that you could run a 50/50 mix with water wetter. the bottle says to use 4 capfuls, which is what i was using. i will try that, though.
im also going to try a kx500 rad cap. that seems like the ticket since every time i ride (track, trail, putting around) theres always some coolant in the overflow bottle... when the engine is cool, the bottle is empty.
now, ive heard you mention the two2cool stuff, but i havent seen it for sale anywhere. where do you get this stuff? thats the kind of stuff i need. you see, i take it you ride trails, i ride tracks alot. after i go out for 20 laps, the ignition cover burns my hand, forget the clutch cover cuz that thing is red hot (ok, not actually red). but its really really hot.
in addition to all of this, i will get the boyesen pump. doing all of this stuff should drop alot of the heat build up, and allow my stock rads to handle the heat of this engine. thanx for the info, nc. :cry: :cry:

  • ncmountainman

Posted November 05, 2004 - 10:34 AM


mx south in FL is where i got mine,it takes 2 oz. per oil change and an 8 oz bottle is $20 plus shipping. seems to be worth it especially if your that hot! they told me the hotter your bike runs now the better it will work! :cry:

  • Jetster220

Posted November 05, 2004 - 12:38 PM


Also can order it from here www.two2cool.com.

  • R_Little

Posted November 05, 2004 - 01:13 PM



If your bike boils over all the time I'd suggest replacing the rad cap with a new one or a 1.6 as suggested. These things wear out over time and they don't hold pressure and the coolant boils.

I've struggled through more than 1 enduro in the "C" class stuck in the mud in 1st gear for miles and my WR only boiled over once when I was positively stuck in slop above the engine cases, and that was with a stock 1.1 cap.

I run all kinds of slop first gear trails and have never boiled it since, even stuck in bottlenecks behind 50 riders.

Maybe your jetting could be a little lean. Try a richer main and turn the fuel screw out a bit and see if it help.

  • tool

Posted November 05, 2004 - 06:04 PM


These things wear out over time and they don't hold pressure and the coolant boils.

Maybe your jetting could be a little lean. Try a richer main...

thats got to be it, because it seems to overflow really easily. just from starting it up and riding for a few minutes. i might as well go for the 1.6 though, because the cooling system isnt quite sufficiant now. but its probably the worn spring.
the jetting might have been lean, but i just richened both the PJ and MJ. but the fuel screw is still at 3 turns out. it was at 5(!). i guess i need a 45 PJ. :cry: the engine really suck gas now. :cry:
BTW - r little, im diggin the look of that swingarm. :cry: that thing is light too. thanx man. works great

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