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450FX oil change gas smell

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Hi Guys, I recently changed the oil in my 16 YZ450FX. The old oil smelled a lot like Gas. I haven't experienced this on previous dirt bikes. Anyone know what may be the cause of this?

 

Thanks

 

Love the bike!!

 

 

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The injector is leaking when the motor is off, and the next time you start the bike the un-atomized fuel gets past the rings and down into the crankcase.

Hundreds of posts on the subject in the Honda forum.

No real evidence of it in the KTM forum.

 

Why it is leaking is a subject of lengthy debate.

 

Bottom line is, the residual fuel under pressue inside the fuel line after the pump and before injector, is leaking out of the injector nozzle, and getting into the engine past the rings.

It could be debris, it could be wear, it could be corrosion.

 

In my opinion, Ethanol in the fuel is creating deposits inside the injector, and causing corrosion and debris. 

You have to pressue clean the injector, treat your gas for ethanol poisoning, and filter your fuel before it goes in the tank or with a tank sock.

If the injector is badly damaged, it has to be replaced.

With Ethanol fuel, this could happen in a few tankfuls of gas, if the bike sits a lot....

 

There have been several 'solutions' in the Honda forums.

No real evidence of any of them working, other that what I mentioned above.

 

  • When you shut the bike off, make sure you do with the kill button, and with the throttle open. Do not stall-kill the motor.
  • Do not start/stop/start the bike. 
  • Always leave the piston at TDC when you shut off the motor (using the kick starter to do so) so any leakage is better sealed from the crankcase
  • Properly seat the rings on a brand new motor (first 10 minutes from brand new) to keep gas from leaking past when the motor is off....and have a better running motor....
  • Install a fuel pump shut off switch, and turn off the fuel pump 10 seconds before you kill the motor. Don't let the pump run dry!
  • Keep the front wheel elevated substantially when the bike is parked

Honda officially says 'it's not a problem unless you let the fuel become more than 15% of the volume. Regular oil changes every ride should solve the problem "

Edited by KRANNIE

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Krannie, thanks for the response. I will try to run ethanol free fuel when possible. 

 

Motohead, It was the second oil change so not break in oil

 

I'll see how it is next oil change, I had an RXV550 and an WR250R, both fuel injected and neither exhibited this issue. I ran exclusively fuel containing ethanol in both of them

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What have the outside temps been for you?  In the snow bike circles it's not uncommon to hear of gas in the oil, when the ECU sees that the engine isn't warming up to temp it increased the fuel output to try and resolve the problem.

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What have the outside temps been for you?  In the snow bike circles it's not uncommon to hear of gas in the oil, when the ECU sees that the engine isn't warming up to temp it increased the fuel output to try and resolve the problem.

 

This is far more likely than a leaking injector.  It's a common remark ever since 2010 when the bike gets ridden in low outdoor temps.  The system stays rich because the coolant temperature never goes up.

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The cold weather theory makes sense, I have a 16 450F and a 14 RMZ 450 and i leave fuel in the tank and I have not smelt gas in the oil. I do use fuel stabilizer and live in socal, not very cold here. Keep us posted please.

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The cold weather theory makes sense, I have a 16 450F and a 14 RMZ 450 and i leave fuel in the tank and I have not smelt gas in the oil. I do use fuel stabilizer and live in socal, not very cold here. Keep us posted please.

It makes sense because it's a fact.;)

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This is far more likely than a leaking injector.  It's a common remark ever since 2010 when the bike gets ridden in low outdoor temps.  The system stays rich because the coolant temperature never goes up.

 

I used to see this pretty often when I worked at a Can-Am dealer. The Early fuel injected ATV models (around 08 I think) used to have this issue fairly often. It was usually fixed with replacing the injectors (V-twin motor). Obviously there is a huge difference between Can-am v-twin ATV's and Yamaha single cylinder dirt bikes however the symptom is identical and small engine fuel injection is small engine fuel injection regardless of the brand, Model, or application. 

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Everything has some leakage into the oil, and the less you let it warm up the more gassy the oil will smell, whether that lack of warm-up is due to weather or short trips isn't too important. 

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I used to see this pretty often when I worked at a Can-Am dealer. The Early fuel injected ATV models (around 08 I think) used to have this issue fairly often. It was usually fixed with replacing the injectors (V-twin motor). Obviously there is a huge difference between Can-am v-twin ATV's and Yamaha single cylinder dirt bikes however the symptom is identical and small engine fuel injection is small engine fuel injection regardless of the brand, Model, or application.

There's one key detail your missing in your comparison. Those atv's you worked on have a thermostat that regulates engine temperature regardless of ambient temp and air flow through the radiator. The FI Yamaha dirt bikes do not.

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That's true.  It's completely normal for the rich operation of a cold started engine to force gasoline past the rings and into the crankcase oil.  But the engine normally warms up enough after 15-20 minutes to evaporate most of the fuel back out again.  The trouble here is that the low ambient temps prevent the coolant from getting hot enough to stop the engine from running in the cold enrichment mode, so it's a bit like leaving the choke on all day.  The gas dump past the rings never stops. 

 

The easiest fix for this is covering part of the radiator set.  Guys up in the north border states that do that usually hide between half of one up to one whole radiator from the wind.  They say it helps.

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There's one key detail your missing in your comparison. Those atv's you worked on have a thermostat that regulates engine temperature regardless of ambient temp and air flow through the radiator. The FI Yamaha dirt bikes do not.

 

Good point.....

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Do any YZs have thermostats? If not, why not? Just the extra weight?

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Do any YZs have thermostats? If not, why not? Just the extra weight?

No none of the YZ's have a thermostat. These are considered closed course competition bikes.

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Sounds like it's time for a thermobob kit ! I got mine originally for snowbiking but I leave it on all year and monitor my temps.

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No none of the YZ's have a thermostat. These are considered closed course competition bikes.

I just don't see any real downsides to having one, but maybe I'm missing somethinig. What kind of course you're on will dramatically impact how hot it runs. 

 

Is there any reasonable way to add one? Would be nice to at least add one to my WR which I guess doesn't have one either.

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I just don't see any real downsides to having one, but maybe I'm missing somethinig. What kind of course you're on will dramatically impact how hot it runs. 

 

Is there any reasonable way to add one? Would be nice to at least add one to my WR which I guess doesn't have one either.

 

If it fails, you have no cooling.........

 

Unless you have a need to run the bike 'hot' (like ice riding riding), I can see no reason to have it.

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Given how reliable they are in cars and trucks I doubt problems would come up often. I'd expect the rate of damage due to failure to be significantly lower than the extra wear due to running cold all the time.

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Is there any reasonable way to add one? Would be nice to at least add one to my WR which I guess doesn't have one either.

 

http://shop.watt-man.com/Snow-Bikes_c7.htm

 

Depending on radiator hose sizes on the YZ, you may also be able to run a KTM housing and thermostat.  I bought one for my KX but never installed it, not sure if the YZ uses the same size hoses but I'm guessing it would be at least close enough to work.

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