HELP! YZ426 Leaking Coolant

When I first bought the bike the previous owner had been using a very cheap coolant so the bike was over heating left right and center...after 20 mins it would puke out coolant and basically the entire rad would empty out!

I have since flushed the rad and it seemed there were no blockages, and replaced the old coolant with Engine Ice, the bike runs much better however after so long a lot of the coolant is leaking out the over flow hose.

We were riding on a VERY hot day and my friend who happens to also have a 426 was riding with me and his seemed to be leaking out at about the same rate but every time we checked his coolant level it was about the same and mine was leaking below the rad gills....as in you could no longer see coolant inside.

What could this be? the bike runs amazingly well other than that, starts first kick other than if it's a hot start, but I think that is due to a fouled up plug which I will be replacing.

It pulls hard through all gears and otherwise runs like a champ!

Please any and all suggestions are welcome!

1. Too much coolant: it will puke it out on the overflow hose

2. They like air flow: if you stop and let it running in a couple of minutes it will boil

3. If it boils too much, the head-gasket could be the problem

Have the cap tested.

1. Too much coolant: it will puke it out on the overflow hose

2. They like air flow: if you stop and let it running in a couple of minutes it will boil

3. If it boils too much, the head-gasket could be the problem

Alot of people have said head gasket but it is only leaking out of the over flow...what other tell tale sings should I look for to inspect for blown head gasket?

On my RMZ450 the only symptom of my blown head gasket was the coolant out the overflow.

Even when i pulled the head off the gasket looked fine & i thought i'd wasted my time but when i put it back together with new oem gaskets the problem was gone, never lost coolant again.

check the impeller cover. if there's spooge there then its the impeller seal. on my 2006 yz450fv, changing the impeller seal(s) was easy, and it fixed right up. Bronco

check the impeller cover. if there's spooge there then its the impeller seal. on my 2006 yz450fv, changing the impeller seal(s) was easy, and it fixed right up. Bronco

Sorry what do you mean by spooge?

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