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Yz450f coolant leak


BradZ
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Hey guys, noticed after a ride yesterday that my top radiator hose was hissing and bubbling at the clamp, and also where the coolant line goes to the head ( not the water pump) it seems to be weeping from there. Enough to drop half a radiator worth over night. Unless its also leaking when I ride. Any ideas what it could be?

Ps. Oil is not milky

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Hesitate to say it but Head gasket gone perhaps? Does it only come out when it's hot or all the time?

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Unfortunately it does sound like that doesn't it. With most water cooled vehicles there is some water in the oil or oil in the water, have you found anything like that? Best to check I suppose as it will knacker the engine if you run it with a gasket blown, it might be possible that your head bolts are not as tight as they should be have you tried retorqueing the head up to the correct adjustment? A cheap fix if that's what it is otherwise your off the the shed with a gasket set and a few late nights.

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Hate to be the bearer of bad news but it could be a cracked head or cylinder,the spark plug will be clean as new.But the only way to know is to pull the head off and depending on how many hours are on the motor you might as well change the valves while your there,and install new rings measure the bore.

These bikes are high maintence,failing to replace valves will cost you large when one snaps and they will snap.

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Oh God that sounds horrible, why on earth would you make a bike that needs that much care and attention? I've had girlfriends that took less care than that!

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2 words Slice Race Bike is why,the service intervals are measured in hours 10 to be exact,not miles motors that rev to 16k with ultra light weight parts need to be cared for. You can't even bore the stock motor you have to replate the cylinder as there is no steel liner to bore.

Thats why alot of guys put the big bore kit on when replate time comes the cheap ones are about the same cost as replating at about 600 usd ,but when they bore the cylinder +3mm over it leaves way less meat to take the heat away and they crack easier. I am not a fan of them they only give a small increase in bottom end power but put alot more stress on the crank so you end up changing cranks/crank bearings more often.And with a slipper piston only 1.5 inches tall the side loads are greater on the bore

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Your getting pressure in the system then you have to find where it is comming from, so check every thing means a rip down. Check the surface of the head and barrel for scratches ( even small ones),,, to and from,, the gasket sealing surfaces .

Get a glass plate and check for wrapage of the block and head.If you haven't done it before simple enough place parts on glass plate,set on greese on a solid surface and try to fit feeler gauges under in varrious places around part. with a heavy block on top of part.

You can tape wet dry paper to glass plate and go in a figure 8 pattern to even out any warpage/scrathces but be carefull of your valve clearences to pistion.

You will need to make sure you don't fix 1 problem to only creat another by checking the valve clearence to pistion if you have to remove alot of head and barrel material ..If that is even the problem. Check it all out don't rush to concolusions

Flip..out!

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First I doubt its a 500 kit most likely a 473-8 kit and no the stock won't work,just google big bore kits for your bike and pick a supplier,has to be one in OZ if not plenty here and the USA.

Not to knock Athina but they are considered the cheapest quality amongst the big bore comunity,and wiseco the best but you pay for it.

As you cant ride the bike anyway I would pull the top end off and check it only a couple of hours work no point in ordeding anything till you know for sure what is wrong. You can do it with the motor in place but it's easy to pull the motor

And while your waiting for parts you can recondition the head.If you order a gasket and find a cracked barrel then your going to need a full kit anyway.

Lots of cracke barrels wont leak coolant into the motor as the crack only open's when hot and above the piston

Edit some replating companys have a exchange program so you need to send your old barrel to get a new one.

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Im having trouble finding a gasket for my bike, being bored out I need a specialized gasket, not oem. My question is if I could find a wiseco gasket out of their big bore kits would it suit my Athena kit? I've heard Athena gaskets are junk

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