WR coolant overflow bottle question......

:usa:Anyone run into problems removing the coolant overflow bottle on a WR? Why is it there anyways....mine always stays at the same level. :)

Mine has been off since I brought it home. Never overheated. I live and race in Ohio and not the desert. It may be helpful in the desert heat.

If you ride tight single track trails and have to stop & go a lot (especially in the Summer), you'll hear the bottle and tubes make a lot of noise as they exchange fluid back & forth into and out of the radiators. I have had my level go down and have had to add more fluid from time to time. If you do a lot of slow stuff, I would keep it on - if you never go slowly but are mostly on the tracks or wide open trails where you can get good air flow then you might consider getting rid of it. I don't see why you really would want to get rid of it other than saving a few pounds since it comes in handy when the radiator needs more fluid - without it, if the radiator needs more fluid, you're SOL and could fry your engine in the tight stuff before you know that you're low on fluid... :)

I took mine off when I bought it. Have never overheated.

Aren't the WR radiators bigger than the YZFs, partially to compensate for stop & go and slow (limited airflow) riding? :D

Don't all deep woods riders carry drinking water which they could add to their radiators (after cool-down) in an emergency? Of course there is always recycled beer as a last resort! :)

I have just bought a 03 WR250F and the Gent I bought it from has basically turned it into a YZF with E-start :D so yes he took the overflow off, and raced Harescrambles with it all summer, and from what I understand, it never was a problem for him, I have Race/Rode it 5 times since I have had it, and have had no problems, I have the overflow so if it becomes a problem this summer with me racing the H/S series I would prolly put it back on, but till then, I will run without it..Just a matter of what you want to do with the bike, if ya trail ride mostly for fun, I may want it left on, Its all about what you think you want with the bike.

Bob :)

Lemme give you my situation since I live in AZ and it might be a little warmer here than the other peples posts. Wrooster suggested removing mine awhile back because I was asking him about reducing the weight. I was worried because I was thinking it's there for a good reason. Anyway, I removed it at the end of summer and checked the fluid in the radiator before I rode off. I just rode around my local jumps area for about 1 hour, couple jumps and paths, on and off kinda riding. When I got back home I saw that the level did go down about 1/16, about a little lower then where the top of the bars or whatever you call them that are inside the radiator are. So I put it back on cause I don't want to take the chance. Now I check it every time I go out and it's always fine, so I figured it needs it. Maybe I need it more cause it's freaking hot here! Hope that helped! I don't know what part of Cali you live in.

I live in AZ too and have never even thought about removing the bottle after seeing a buddy with a yz426 spew coolant all over the place every time we stopped on a trail ride. Could have been him, could have been his bike (it was pretty beat up) or who knows what? But the way it spewed every stop made me think the overflow was on my bike for a reason. Do I have any evidence that my bike really needs it? Heck no! But seeing him overflow like that all the time gave me pause!



just my $0.02 on this...

if your engine and radiators fins are clean, you will probably never boil out into the overflow tank unless it is above 95'F [35'C] and you are sitting idling for a bit (have had that happen a few times while waiting for friends extract themselves from whatever they rode into). but if you are moving at a good clip, and not at redline the whole time, more than enough air passes through the radiators to keep from boiling out.

// BUT // BUT // BUT //

if your engine is encased on caked-on mud, and the radiator fins are somewhat clogged with a combination of roost from the guy in front of you and other collected trail debris, your bike will puke into the overflow bottle at much lower temperatures. i rode one really muddy sunday on some rocky trails in PA and boiled it out a couple of times even though it was like 75'F [24'C] out. this happens generally when you are stuck in some mud hole and trying to get moving again. no forced airflow through the radiators plus the fins being clogged up with crap = very poor heat dissipation.

(in these types of situations i have found it useful (at least on '01 and '02 bikes) to spread your knees outwards in the fast straight sections to allow more air to come through the radiators and keep the motor cooler. the natural seating position leads to your knees "clogging up" the air portals on the radiator shrouds.)

jim aka the wrooster

'01 wr250f


Ok Wrooster.. who's bike is that? I know that's not yours, you could eat food off yours it looks so clean in the other pictures I've seen! :)

Jim, your bike looks pretty clean comparing to some of the rides we've been on... :D:)



Jim, your bike looks pretty clean comparing to some of the rides we've been on... :D :D

err, umm... if you go faster some mud falls off??? :)

jim aka the wrooster

'01 wr250f

Isn't the over flow tank and EPA requirement because the bike is not a "closed course only" bike? They need the over flow catch tank to get a green sticker in California I believe. EPA doesn't like the antifreeze spilling on the trails. Did you guys see the 1st SX race in the mud bog in Spain this season? Some of those bikes had a steady stream of white steam coming out of the radiator boil over hose. Good thing they didn't have to ride 35 miles back to the truck!

My WR has boiled a couple of times from going really slow for a long time--especially when I was trimming my singletrack loop. I had clippers and a saw with me and would stop and trim, leaving the engine running. I have never added nor lost any fluid since I got the bike new in '02. But it has boiled a few times.

The radiator on the WR does have an extra cooling fin row, but that in itself is not enough to cool it on slow trail rides, or lots of stop and go riding. I thought at one time it would be cool to carry extra gas or drinking water in that little tank, but after the first time I boiled it, I gave up those thoughts. My son's YZ85 only has a radiator on one side, and usually, after a hard weekend of trail riding, he needs more fluid. He shuts his bike off every time we stop, but it's a breeze to start compared to mine!

Somebody mentioned using your Camelback water on the trail to refill a radiator...why waste water when a couple of your buddies can just pee in it! First time I rode with this crew I pulled up to hear "don't burn your johnnie!!!" as they filled the left shroud.

PS Hot urine stinks!

i always filled the bottle, always over heated, untill i change the coolant.

i always filled the bottle, always over heated, untill i change the coolant.

Changed your coolant from what to what?

Isn't the over flow tank and EPA requirement because the bike is not a "closed course only" bike? They need the over flow catch tank to get a green sticker in California I believe.

F.Y.I, The WR is not a green sticker bike.It should be, but for political reasons it's not.

I removed the bottle on my 01'. I cut and tie wrapped the overflow hose just above the exhaust header. This way when it does boil over I know it right away and I can turn the bike off or get moving. the only time it boils over is in the summertime and I stop on the trail and let the bike idle for a while.

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