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BMcEL

2008 YZ450F Excessive Oil Use

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Converted a 2008 YZ450f for street use and it's using a lot of oil. Never burned oil before and it doesn't smoke. No leaks. I've been riding it around town and the oil level stays normal but I ran it on the highway for about 70 miles at about 6500 RPM and the dipstick barely touched the oil afterwards. Again, it doesn't smoke, runs great, and there are no leaks. Any ideas? No excessive oil blowing out of the breather tube either. I'm running Rotella T6 BTW.

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Converted a 2008 YZ450f for street use and it's using a lot of oil. Never burned oil before and it doesn't smoke. No leaks. I've been riding it around town and the oil level stays normal but I ran it on the highway for about 70 miles at about 6500 RPM and the dipstick barely touched the oil afterwards. Again, it doesn't smoke, runs great, and there are no leaks. Any ideas? No excessive oil blowing out of the breather tube either. I'm running Rotella T6 BTW.

 

Try it again. The only way my YZ'd WR450 Supermoto used to spit oil out was the breather hose when it was overfilled. I drain it after about three or four rides and only put a quart in it. We also use the Graves racing oil seperator. However it will still puke out if overfilled.

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Never put more than a quart in it. Even if it was overfilled, wouldn't it only blow oil until the level dropped to normal? 

 

I've ridden this bike all over off-road, at the dunes, plenty of sustained high RPMs and it never used oil. I've seen the Graves separator before and maybe that really is what's happening. You would think there would be oil all over my boot and back tire if it was blowing that much out of the breather though. 

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Never put more than a quart in it. Even if it was overfilled, wouldn't it only blow oil until the level dropped to normal? 

 

I've ridden this bike all over off-road, at the dunes, plenty of sustained high RPMs and it never used oil. I've seen the Graves separator before and maybe that really is what's happening. You would think there would be oil all over my boot and back tire if it was blowing that much out of the breather though.

As long as you don't put more than a quart in it you shouldn't need the graves deal. Also if you let them sit for a while they may read low on the dip stick. When warmed up it will read full.

In any case just try it again. Yamahas are pretty oil tight.

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An '08 only holds a quart on a no-filter oil change; only 1 liter with a filter.  If more is added, it will not fit in the "tank" section in the front of the engine, so it gets forced out through the top at the pressure balance hose that connects to the right crankcase cover and goes back to the sump.  The return pump picks it up and tries to send it back again, but with the same result, because there isn't any space in the tank for the extra.  All it does is raise the level in the sump, which causes an excess to be slung off the crank, which leads to more oil out the breather, and can overwhelm the oil rings and cause oil to be burned.  Simple waste of money and a loss of power to overfill.

 

The dip stick barely touching the oil is a loss from the full mark of maybe as much as 100cc.  If you grant that you ran your 70 miles in an hour, just to keep things simple, then you're burning 100cc/hour at 6500 RPM, which works out to .0005 cc per each individual power stroke. 

 

With that in context, there are only two places for oil to enter the combustion chamber and/or exhaust , and those are the rings and the valve seals (if you rule out an oil leak from the top end feed through the head gasket).

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An '08 only holds a quart on a no-filter oil change; only 1 liter with a filter.  If more is added, it will not fit in the "tank" section in the front of the engine, so it gets forced out through the top at the pressure balance hose that connects to the right crankcase cover and goes back to the sump.  The return pump picks it up and tries to send it back again, but with the same result, because there isn't any space in the tank for the extra.  All it does is raise the level in the sump, which causes an excess to be slung off the crank, which leads to more oil out the breather, and can overwhelm the oil rings and cause oil to be burned.  Simple waste of money and a loss of power to overfill.

 

The dip stick barely touching the oil is a loss from the full mark of maybe as much as 100cc.  If you grant that you ran your 70 miles in an hour, just to keep things simple, then you're burning 100cc/hour at 6500 RPM, which works out to .0005 cc per each individual power stroke. 

 

With that in context, there are only two places for oil to enter the combustion chamber and/or exhaust , and those are the rings and the valve seals (if you rule out an oil leak from the top end feed through the head gasket).

 

I don't know how to make it any more clear...the bike was not, and never has been, over-filled. I always drain the oil warm and have never put more than a quart in it, even with a filter change. The bike has also never burned oil and wouldn't just start burning oil overnight.

 

I did some more research and it turns out it's pretty common for YZFs to blow oil out of the breather at high RPMs because of the lack of a baffle in the breather circuit. With the amount of highway riding I did recently, the oil could have blown out slowly and without making a mess. Going to put a catch can on the breather and run it on the highway some more. If that's where the oil is going, an oil separator with a return line to the tank should fix it.

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I have a 08 450 and under high R's or high temps it will push some oil out the breather hose. Do the oil breather hose mod. This fixes the oil pushing out. Also have noticed if you check the oil directly after riding it will almost always read on the low mark. Wait about five min then check.

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