2005 yfz 450 leaking water

[HeWasRidinDirty]

Hello all. I got this yzf for almost nothing. It's in pretty good shape. However, it's pretty stubborn on cold start-up. I noticed while cranking it over that there was water dripping from what appeared to be the exhaust where the pipe bolts on. It did fire up and I could smell coolant in the exhaust. The P.O has installed a toggle switch for the cooling fan. I'm thinking that maybe it overheated and cracked the head or something? Any tips/ advice is much appreciated. 

 

[Frank Angerano]

Welcome to Quadcrazy, hopefully it’s not a cracked head and maybe just a head gasket. 

New gasket kit prob about $40 for the entire engine  on amazon. 

As far as the fan switch I’m not a “fan” of that. No pun intended. Unless that fan is wired to come on and shut off with the ignition instead of a switch I would be worried. I would actually look into  a replacement temp sensor that brings the fan on and look into the wiring diagram to see if you can restore the fan circuit to factory operation.   

Other then that you should be good to go. The bike appears to be in decent shape. 

 

Merry Christmas 🎄 

[wanrep]

Unless it sat in subfreezing temps with straight water in the cooling system, it's doubtful the head is cracked.  Worse case, the head might be warped if it really got hot.  More than likely you can get by with a new head gasket and I'd definitely get that fan switch working properly.  It's all in the factory service manual.

[HeWasRidinDirty]

Thanks, peeps. I'll probably start on it tomorrow and see whats what. 

Merry Christmas! 🎄

[HeWasRidinDirty]

I haven't been able to tear into it yet. Other things....... But, I did notice that it says Athena on the cylinder. Aftermarket cylinder right? Oh, boy.....😬

[Frank Angerano]

Yuuuuuup! 100% aftermarket.  

Maybe look into eBay for an oem used head. 

 

[HeWasRidinDirty]

I haven't quite got the head off yet. I'm close. The thermo switch for the fan is no good. I've checked that. I'm studying the service manual some before I go tearing the head off. It's close to coming off. I just gotta get the camshafts out and the head bolts off. Everything else is off/ disconnected.

[Frank Angerano]

Great job! Looking at that manual before tearing into it is a smart move.  Take your time. Lable things with painters tape and a sharpie and take a few before pics for reference. 

Post a few pics of you can.  

[HeWasRidinDirty]

Yep. Here we go. It looks like some corrosion on the cylinder head. It's right on the edge of the combustion chamber. That's gotta be where the water is leaking. I noticed that there is water in the oil too. Looks like someone put a big bore kit in this thing? 95mm is stock bore. 

[HeWasRidinDirty]

8 minutes ago, HeWasRidinDirty said:

Yep. Here we go. It looks like some corrosion on the cylinder head. It's right on the edge of the combustion chamber. That's gotta be where the water is leaking. I noticed that there is water in the oil too. Looks like someone put a big bore kit in this thing? 95mm is stock bore. 

What would cause the corrosion like that? Extended sitting? 

[Frank Angerano]

Could be a number of things.  One being the alkaline in the coolant, second could be the soft metal being eaten away from electrolysis, or just improper tightening of the head and allowing coolant to slip by and start eating away at the soft metal.

you could try to put two new head gaskets back In place but my guess it will fail eventually. I would try and locate a used  oem head maybe on eBay and go with that. If it was an oem head you could have it milled down a hair. I just don’t know how an aftermarket head will work out with that. 

[wanrep]

Pretty sure that's the original head. You'll have to take the head to a competent machine shop and have the head milled a few thousands to get a good sealing surface again.  Get the head gasket from Athena for the 98mm piston.  BTW....that piston has 12:1 compression.  Be sure to use one of the aftermarket coolants or distilled water and antifreeze.

Coolant in the oil means water pump seal is leaking.

 

[HeWasRidinDirty]

8 minutes ago, wanrep said:

Pretty sure that's the original head. You'll have to take the head to a competent machine shop and have the head milled a few thousands to get a good sealing surface again.  Get the head gasket from Athena for the 98mm piston.  BTW....that piston has 12:1 compression.  Be sure to use one of the aftermarket coolants or distilled water and antifreeze.

Coolant in the oil means water pump seal is leaking.

 

Idk if it can be milled down far enough to get a smooth surface again. So, that piston is 3mm over stock. That's a big jump. So the stock head can be used with that big of jump? 

[wanrep]

Yes, stock head works fine with the Athena 98mm kit.  I don't know how much milling would be too much.  There's a couple guys over at www.yfzcentral.com that could tell you. There's different thicknesses of base and head gaskets available to compensate for a milled head but I'm no expert when it comes to that.

[HeWasRidinDirty]

Ok, thanks. I'm gonna look into that. 👊

[06kfx440]

Did any gaskets come off of that? Worst case scenario, buy a used head. I would have compression tested to see if air was leaking. Water corrosion is from water sitting on the surface. Since your in to the motor anyway. Check all your seals.

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