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al-yfz

Yamaha
yfz 450 water pump leak solution

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I recently bought a band new 2004 yfz450 and it was leaking prestone off the weep hole , i brought it 3 times in 2 months to the dealer,they change the shaft, seal .bearing all 3 times . the last time i brought it to the dealer, i looked at the inside of the engine and i check the inside hole of the balancer shaft where the water pump shaft drives into and it was way to big . So yamaha canada is going to change that shaft free of charge . so everybody out there that there bike's are leaking, open the water pump cover where the impeller is and take a dial indicator and check if you got side play ,my bike had .019 :bonk::bonk:

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i went to the delear with the exact problem. the tech guy i talked to said he had a yz450f (almost the exact same engine) and it did the same thing. what you need to do is let the engine come to full opperating temp. might take a few mins but the leaking then stops. at least for me it did. it does leak a few drops every time you start it though... just a common thing w/ the 450 engines.

hope it helps you out

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yes , mine does the same thing it leak's while it's cold but as soon as it get hot it stops leaking ! i went to the dealer today to see the new balancer shaft that they ordered but the hole inside seem's to be too big. we measured it and it was .009 loose so they are going to install it anyways. we are going to see

afterwords if it leak's , where going to machine a bushing that goes in the balancer shaft . after the warranty . i know it's not leaking much but i say a machine is not suppose to leak oil or prestone . I will keep you posted if i got any more info regarding my yfz . thanks !

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Same Thing Waqs Happenig On My Yz450f When The Engine Is Still Cold But As Soon As It Warmed Up The Leaking Stoppes. Its The Oil Seal That Hasnt Taken Its Expansion.

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I just got my yfz back from the dealer yesterday and i opened my water pump cover and measured the side to side clearance .I got a reading of .004 this is big improuvement from last time . and i started my bike whithout the cover and you can see the impeller turning whithout going side to side . the reason why those yamaha yfz 450 or yz450f are leaking while there cold is because the shaft is going side to side and the seal is to hard so it doesn't follow but when it get's hot the rubber of the seal get's soft so it doesn't leak anymore . so i chalenge anybody out there if your bike leak's take the cover off and take a dial indicator and put it on the end of the water pump shaft and push the shaft from side to side ,take a reading if it's more than .005 to .010 it' probably going to leak!!!!! :bonk:

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I made a new shaft .005 larger in diameter and hardened and polish the surface. In addition, the lengths were changed to reduce end play and sizes of the end of the shaft to fit the slot better to reduce rotational play of the shaft. Haven't hade a problem after that. Its a poor fit using a stock Yamaha shaft. It has too much end play and I suspect that the seal is too close to the chamfer as it drifts in and out while spinning.

I don't have a drawing as I used my stock one as a reference when machining the new shaft. Also I tapped the weep hole and treaded a nipple and attached a clear hose and routed it to a catch bottle. this way I can monitor if it leaks during a ride. I'll remove and inspect it next winter! :bonk: I hope this helps someone who has the resources to machine there own shaft. :bonk:

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Hi, I have an 04 yfz450 and just noticed mine is leaking, I pulled the cover off and I see the water pump impeller, How do I take it off it seems tight and does it have reverse threads? I went today also to Malcolms Smiths and all they gave me were 2-oil seals a copper crush washer and a housing seal is that all I am going to need? Thanks for your help......Steve

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Hi, I have an 04 yfz450 and just noticed mine is leaking, I pulled the cover off and I see the water pump impeller, How do I take it off it seems tight and does it have reverse threads? I went today also to Malcolms Smiths and all they gave me were 2-oil seals a copper crush washer and a housing seal is that all I am going to need? Thanks for your help......Steve

Read this link and see if it answers some of your questions.:bonk:

http://www.yfzcentral.com/invision/index.php?showtopic=53470

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