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valve seals leaking

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Hi my name is David Russell I own a 06 yz450f. This bike has about 300 hrs on it. Noticed that on the last couple oil changes having to add a few ounces of oil. I had subframe off to change shock bearing and looking in intake I notoced oil on both outside intake valves. My question is this do I need to just change seals or ? I am very anal about maintenance, this bike still fires up 2nd kick no problems what so ever. I have changed the timing chain in last 20 hrs oil gets changed 10 to 12 hrs with Amsoil.

Thank You

David Russell

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The phenomena of the center intake being cleaner than the outer two is normal, and points up one of the idiosyncrasies of the 3 valve intake; the bulk of the fuel enters the engine through the center port, while the outer two handle mostly air. The fuel system cleaning additives in the fuel thus do a much better job of keeping the center valve spiffed up, while the outers get a little crustier.

The source of your oil loss is more apt to be rings, but at that much time, a new set of seals and springs won't hurt. One indication the valve seals are leaking is a puff of smoke on start up when the bike has sat for more than a few minutes, or a single puff when coming back on the gas after decel.

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Thank you for the information. What is the recomended replacement hrs or safe zone for the bottom end on these engines. I plan on getting parts together and puting new piston rings seals,springs in it just wondering about bottom end? This bike has been flawless not one problem just getting a little nervous.

Thank you

David

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The only accurate way to rate an engine's longevity is in horsepower/hours. For instance, an engine intended to last for 100 HP/hr can be expected to produce 1 HP for 200 hours, or 50 HP for 2 hours.

That means that the answer really depends on how you use the bike. If it's something you mostly ride trails with, the crank can easily go 300 hours or more. If it's a serious race or practice bike, a crank every year might be wiser.

I've often thought that rather than log hours, tracking total fuel used would be a better way of measuring engine use.

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I'm a 43 yr old C class rider I do 2or 3 hare scramble races a yr. I can usually finish in top 25 percent of class. The rest of the time is trail riding. The bike has hit rev limiter maybe twice in its life. I havent noticed any smoke at all. I apreciate your time and knowledge. I think I will gather up piston kit valve springs keepers, retainers and go from there.

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I'm a 43 yr old C class rider I do 2or 3 hare scramble races a yr. I can usually finish in top 25 percent of class. The rest of the time is trail riding. The bike has hit rev limiter maybe twice in its life. I havent noticed any smoke at all. I apreciate your time and knowledge. I think I will gather up piston kit valve springs keepers, retainers and go from there.

by anychance do u have a hourmeter on your bike. because if you do have a soild 300 hours on your bike that just proves the point that theses motors are amazing

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I dont that is where the problem lies I'm guessing I bought the bike new in March of 07. I do keep a note book on the hours for changing oil but its just guess work. I might be off by a few hrs but it should be pretty close?

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I dont that is where the problem lies I'm guessing I bought the bike new in March of 07. I do keep a note book on the hours for changing oil but its just guess work. I might be off by a few hrs but it should be pretty close?

yea thats what i did untill i got the hourmeter. it take the guess work out of doing work on your bike like oil and stuff like that..

its funny me and my buddys would go on a ride and be like damn we rode all day we had to do at least 6 hours of riding. now they say the same thing but i look down at mybike and be like hey we only did 2.5 hours worth..

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I usually figure about about half the time we are gone is actual running time. I will put a hour meter on when I tear into engine this time.

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I had an 05yzf450 and it started burning oil not long after it had a new piston rings, head, timing chain etc. Would race one day and check oil, had to add a lot.

Now my 06 with minimal hours is burning oil. Smoke on startup. Would that be the rings or the valves and seals. Was thinking more the rings. If it was the seals, wouldn't there be oil in the exhaust head pipe, or would it just burn off to fast to notice if i took the head pipe off. I did a top end and checked valves on a buddies bike last weekend and found that one of the exhaust valves wasn't closing all the way due to carbon build up. We just cleaned the head and valves/seats and put new seal on that valve. New pison/ring/timing chain. Runs great. His was burning lots of oil too. What is an average amount of oil to be losing on lets say, a race day. 15 minute practice, 2 15-20 minute moto's.

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