Help with Running temp on a yz426f

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Judge

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Just wondering if anyone would know wat temperature a yz426 would run at only had the bike a month an the last couple times of riding the bike when I've stopped I've notice water coming out from the over flow hose after switching the bike off the bike this has only been happening since i done a service on it i changed all fluids not sure if its overheating ,I've brought a hand held temp gun that u point at an area an it give u a temp reading an it was around 140 on the cap side of the radiator an the opposite side was around 100 is that normal
 

my67xr

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140° C is a bit hot, 50/50 coolant/water boils at 270° with a 1.1 bar cap (16lb)
Have you ever replaced the radiator cap?
Next thing is to get the radiator checked that isn't blocked, and then check that the water pump impellor is still good
There should be a temp difference between the inlet and outlet, but that's a bit much.
Was it idling for a while before you shut it off ?
 

Judge

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Na it wasn't idling for long around 30 sec how would I check if the radiator is blocked ,ill pull the hosing off an check the impeller an I've put a new cap on it
 

china911

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it may be that who ever drained the coolant last time around never bleed air out of the coolant system .

if you look around the engine barrel you may have a Phillips screw ,or a 10mm bolt. You will need to tilt your bike to the side .(around 60 degrees undo the screw/bolt let the air come out . When the coolant come out screw it up again. top up as needed. Also if yore riding a lot of goat trails . you can change the ratio of coolant say 70 % coolant 30% demineralised water.
 

Judge

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Is that bolt on the barrel or isit the bolt around the impeller shaft to drain the coolant out
 

china911

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the impeller bolt would be the drain plug. l used to service my nephew wrf 250 and pretty sure it was on the barrel ..you can always try (cold engine) tilt the bike then removing radiator cap. this may release air.
 

GooseMan

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Was the weather hotter than when you normally ride? Does it have an expansion chamber? What happens if you keep riding?

If the guy you got it off just topped up the coolant up than it will push out any coolant it doesn't need and find its own level. If you keep riding and the level drops below the core of the radiator than it could have a over heating problem or worse a head gasket leaking. My GasGas does this, it will stop overflowing when it reaches the coolant it wants, but if I ride on a day that is hotter than normal it will push put just a bit more as it runs a little hotter.
 

Judge

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I think I found the bolt nothink is coming out does the bike have to be running while the bolts out
 

Judge

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Was the weather hotter than when you normally ride? Does it have an expansion chamber? What happens if you keep riding?

If the guy you got it off just topped up the coolant up than it will push out any coolant it doesn't need and find its own level. If you keep riding and the level drops below the core of the radiator than it could have a over heating problem or worse a head gasket leaking. My GasGas does this, it will stop overflowing when it reaches the coolant it wants, but if I ride on a day that is hotter than normal it will push put just a bit more as it runs a little hotter.

It was abit hotter but not to much an I changed the coolant in the bike but I didn't know about air could be caught in there
 

my67xr

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I think I found the bolt nothink is coming out does the bike have to be running while the bolts out

If it's anything like a car, start it up with the bolt out, then top it up while it's running.
Water/Coolant will come out and might have bubbles of air through it, keep topping it up until straight water/coolant comes out then refit the plug

Where it is coming out is that the overflow bottle ?
If it's out of the radiator overflow hose, then the bottle has been taken off ?
 
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china911

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water will be there regardless . As gravity takes over. l changed mine on my 4 bangers all the time . keep topping up until water comes out continuously. lf no water comes out you have a blockage. As other post say the impeller may of fallen apart and blocked the lines.. The main reasons for bleeding is so you don't get any uneven hot spots around the piston.
 

GooseMan

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is it much coolant overflowing? When you changed the coolant did you put same amount back in? and was it full right to the top? Also a picture of the bolt your taking out would help too, thanks
 

zwebx

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I would recommend replacing the yzf rads with wr rads and or chinese radiators.. and then a thermo fan w/switch...

Dont forget pumping out coolant could be hg or cracked head. not too uncommon to rule out.
 

zwebx

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I would recommend replacing the yzf rads with wr rads and or chinese radiators.. and then a thermo fan w/switch...

Dont forget pumping out coolant could be hg or cracked head. not too uncommon to rule out.
Actually, My yz400 cooks quite easy.. really need to ride around in 2nd gear..
 

Judge

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Guys could it be running hot cause I put the wrong coolant in it I didn't put ethylene glycol just normal coolant
 

china911

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Guys could it be running hot cause I put the wrong coolant in it I didn't put ethylene glycol just normal coolant

nah mate ,you have problem some were. A quality coolant will keep the bike a lot cooler than a pre mix jobbie. By the sounds of your heating up problems you have a blockage. Have you pulled the water pump out and inspected it yet ?
 

zwebx

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nah mate ,you have problem some were. A quality coolant will keep the bike a lot cooler than a pre mix jobbie. By the sounds of your heating up problems you have a blockage. Have you pulled the water pump out and inspected it yet ?
most coolant is glycol. Quality is measured in price and technical jabber on the bottle.
Unless you get a non glycol based coolant.. i use nulons blue stuff been good at a 50% mix up to 130 deg reliably.

Now oils and thats a different subject.

I dont think that will be the issue.
How long does the bike run for before it boils? my yz gets hot in about 60 seconds of idling.. Then riding around can boil easily if speeds slow to slower than 1st gear past about 5k rpm
 

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