Fuel in oil


10 replies to this topic
  • moto762

Posted January 27, 2014 - 09:11 PM

#1

Alright here is my problem shifting has became a problem from 1st to neutral or 2nd to neutral, so I change my oil to a mobile one full synthetic while I am changing my oil I smell fuel. also when I drained both sides clutch and motor, (takes 1qt.) at least two qts. came out.....and smells like fuel. So I changed it rode and pulled the fill plug out and I smell fuel, sight glass is over full as well so.....not sure where to start, replaced fuel pump about 8 months ago due to stalling issue other then that it is bone stock.



  • jakeh_16

Posted January 27, 2014 - 09:59 PM

#2

what model is the bike.

 

fuel in oil sound like a badly worn piston and getting piston blow-by

does the bike blow smoke?



  • grayracer513

Posted January 28, 2014 - 07:26 AM

#3

Since you have a sight glass, and you are in the YZ450 forum, I'll guess that you have a '10 or later fuel injected YZ450.  (it's easier if you say so up front).  Since you're in Wyoming and it's January, I'll assume it's cold. 

 

The injection system automatically compensates for cols starts based on information from the coolant temperature sensor.  If the temp is low, the mixture is enriched, and only goes to a normal, warmed up state after the coolant reaches 120-130 or so.  The trouble in extreme cold weather is that the cooling system has no thermostat, and what with the radiators being capable of managing the heat of the engine running in south Texas in August, the coolant never heats up that much when riding in the snow, and the result is that the engine runs artificially rich all the time.  The additional fuel contaminates the oil.  This issue fairly well known.

 

The simple fix is to cover one radiator while riding in "real" winter weather.



  • moto762

Posted January 28, 2014 - 08:38 AM

#4

The Bike is a 2011 yzf450, it has been an unusually cold winter but I have rode the bike in winters past and never had an issue before with the fuel going into my oil. The bike does have a lot of hours on it with the stock piston, while running the bike the other day if the bike was running overly rich because of the coolant not coming to operation temp wouldn't the bike act like it was running rich? I have not noticed any performance issues bike is running awesome.



  • grayracer513

Posted January 28, 2014 - 08:50 AM

#5

The bike will actually like the rich mixture with all that cold air running through it.  You don't have to believe it if you don't want to, and the problem was worse with the '10's than with the later ones, but it's a simple enough thing to try. 



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  • Darvo

Posted January 28, 2014 - 08:59 AM

#6

The Bike is a 2011 yzf450, it has been an unusually cold winter but I have rode the bike in winters past and never had an issue before with the fuel going into my oil. The bike does have a lot of hours on it with the stock piston, while running the bike the other day if the bike was running overly rich because of the coolant not coming to operation temp wouldn't the bike act like it was running rich? I have not noticed any performance issues bike is running awesome.

 

Grayracer is right - the bike will still run fine when cold, you won't notice any performance loss other than using lots of fuel.

 

In the snowbike world, cold temps are constantly a problem.  The simplest solution for you would be to block a radiator as mentioned, however, I'm not too comfortable with that unless you're monitoring the water temps.  TrailTech makes a nice water temp sensor for around $40.  If you ride a lot in extreme temps (cold or hot) it's worth having one!



  • moto762

Posted January 28, 2014 - 09:26 AM

#7

gray-racer and darvo thanks for the info and I will try it out. just wonder why I wouldn't have had this problem before when I have rode in the winters prior. I am time limited on ideas wanting to go down the the rhino rally in Feb. wouldn't want to drive that far and have my bike fail on me. I have two rides on it with the fresh oil and I would say that there is about an extra qt. of oil out of it. when I rode yesterday it was around 30 deg. with a slight snow fall. Thanks guys for all/any ideas :thumbsup:



  • Darvo

Posted January 28, 2014 - 10:01 AM

#8

gray-racer and darvo thanks for the info and I will try it out. just wonder why I wouldn't have had this problem before when I have rode in the winters prior. I am time limited on ideas wanting to go down the the rhino rally in Feb. wouldn't want to drive that far and have my bike fail on me. I have two rides on it with the fresh oil and I would say that there is about an extra qt. of oil out of it. when I rode yesterday it was around 30 deg. with a slight snow fall. Thanks guys for all/any ideas :thumbsup:

 

 

There are probably several things making small differences that are all adding up.

-More hours on the motor, easier for the extra fuel to get past the rings

-Slightly colder temps.

-Light snow falling, the snow hitting your radiators seems to cool stuff much faster than just air.

-New fuel pump?  not sure.

-You might be giving the bike less time to warm up, not letting it idle before shutting it off, etc.

-Blurping the throttle when the bike is warming up will make it worse.

 

I've done lots of experimenting this winter...  By running a Dobeck programmer, and keeping the water temps up where they should be, my bike burns anywhere from 25-35% less fuel than the guys running stock bikes and not watching their temps.  It's crazy how much fuel these bikes can burn and still run ok.



  • moto762

Posted January 28, 2014 - 04:14 PM

#9


 
Did a lot of thinking today and wanted to try something before I go and ride the bike in the cold again(have a heated garage). Talking with my dad we thought that there had to be some sort of check valve to prevent the fuel from the tank to the fuel injector. Looking into it and found that it goes fuel pump to fuel pump line straight to the injector. So I took the chance and pulled my tank off put it on my work bench and looked into the line a little closer still couldn't find anything. went back to my tank and noticed there was fuel on my bench, lifted up my tank and fuel pretty much just pored out of the fuel line that comes off the pump itself, Sort of shake the tank and pump and fuel just comes on out of the line. I believe that there should be a check valve of some sort on the pump to prevent fuel from flowing out of it. Does any body know for sure if the fuel pump should have a check valve (haven't taken the pump out of the tank yet).

  • jakeh_16

Posted January 29, 2014 - 07:54 PM

#10

check valve or not, fuel can only enter the oil via the cylinder or head. even if its running super rich fuel shouldn't enter oil. if ur bore, oil scraper, and rings are intact fuel cant get down, nor oil up.

 

possible worn exhaust valve seals combined with rich mixture, if fuel is left unburned it will go through exhaust, if valve seals are worn unburned fuel may go up into head (not likely but)

you may have been unlucky enough to have ur engine suck it debris and damage ur engine.

 

I would say try covering 1 radiator since its easy to do. but I don't like ur luck



  • grayracer513

Posted January 30, 2014 - 07:30 AM

#11

check valve or not, fuel can only enter the oil via the cylinder or head. even if its running super rich fuel shouldn't enter oil. if ur bore, oil scraper, and rings are intact fuel cant get down, nor oil up.

 

 

That's factually incorrect.  If you don't think so, take the best sealed engine that you have access to, cold start it and let it run for no more than 5 minutes, then send a sample of the engine oil out for analysis.  The report will come back showing significant fuel contamination to the extent that it might even reduce the tested viscosity by a full grade.  In normal operation, where the engine is run up to full temperatures and kept there a while, that fuel is simply evaporated and disappears within fifteen minutes.  Take the same engine and run it around for 20 minutes with the choke on, then test that batch of oil. 

 

  It's even worse when you have a condition like was common to the early EFI CRF's.  They had injectors that would "drool" under residual line pressure after shutdown.  The liquid fuel simply runs past the ring gaps.

 

As to the pump question, I am not certain, but I believe there should be a low pressure check on the fuel pump, as the OP suspects.  If it's leaking on the bench, as you say, it may be due to trapped debris in the valve, and you may be able to clear it by routing the open fuel line into a suitable container and briefly powering the pump.  Keep in mind a fairly high volume of fuel will be driven through this line under a good deal of force, and gasoline is outrageously dangerous to spray around the room.  Be careful.  The volume delivered will be higher than any normal fuel flow the pump normally sees, and you might wash the check valve clean that way.

 

But even if the check valve did leak, the injector should stop the fuel flow completely.  To test this, remove teh injector from the throttle body with the line connected, disconnect the electrical connector at the injector, and kick it several times to power the pump.  No significant fuel should drip from the nozzle.







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