250F oil kinda smells like gas?

[nikki]

Any possible reasons my 250F oil might kinda smell like gas? I changed the oil last night in it and it sorta smelled like gas. Was a little thinner than new oil but not too thin. Bike runs great so seems strange that there would be some sort of leak. Red did overflow the tank and spill all over the bike last week with gas (and just filled the pressure washer with gas before smelling) so maybe it wasn't related at all... just wondered if there would be any simple reasons if it did smell like gas?

 

[cujet]

It is not uncommon for fuel to contaminate the oil. As a matter of fact, this is a major reason for oil changes. Propane powered engines do not contaminate the oil in the same manner, so the oil changes can often be extended.

Chris

 

[jmics19067]

Cujet is right but here is a couple of mechanical problems that you should make sure you dont have.<depending on the severity of the situation>

overly rich, worn rings and somebody setting on the bike twisting the throttle while it isnt running making vroom vroom noises :confused:

 

[Rich Rohrich]

Nikki - What type of fuel are you running in your 250F?

 

[nikki]

Originally posted by Rich Rohrich
Nikki - What type of fuel are you running in your 250F?

Always run 93 octane... but it may have gotten a gallon of Gas City's race fuel the weekend prior to the oil change.

 

[Rich Rohrich]

What you are smelling in the oil is fuel that never vaporizes or burns and gets past the rings dilluting the oil. The options are pretty simple. Change the oil after every race (a very good idea in general on these engines), and/or run a fuel that will vaporize and burn completely and not leave any liquid fuel behind to dillute the oil.

Dr. Dave Redszus the blender of FirePower race fuels gave me these numbers as typical distillation temperature values at the refinery for Northern Illinois in the summer.
10% - 158
50% - 250
90% - 374
End point - 437

while Phillips B35 looks like this consistently

10% - 156
50% - 204
90% - 217
End point - 250

So what do these numbers mean? Pump fuels, and some of the cheapo race fuels have components that are so reluctant to vaporize and require such high temps that a LOT of the fuel that passes through the jet tends to make it to the combustion chamber in a NON-combustible form (i.e. liquid droplets). If it won't vaporize before ignition then it won't burn. So you end up having to add a bunch of extra fuel to hit your target air/fuel ratio. This is a MAJOR contributor to the spooge problem on two-strokes and the oil dillution issues on four-strokes.

The 250F is even more sensitive to this issue because of the high rpm it makes peak power at. There is so little time to vaporize the fuel that only the lower temp light ends will burn off, the rest goes out the exhaust valve or leaks into the crankcase. It gets even worse here in the midwest during the spring.


The EPA mandates seasonal temp ranges for different areas of the country but there are a couple of key points to remember. The EPA seasonal values only have to be met at the refinery not the pump. The 50% distillation temperature in Illinois (summer) has an acceptable range of 170-250F . Think about that. A single point on the curve can vary by a larger range than most race fuels change from 10-90%, and that is at the refinery point. By the time it gets to your engine the range is even greater.


Pump fuel just can't hang with an engine this advanced. Seeing how many guys who run pump fuel have crank and main bearing problems on these engines makes me think the perceived savings from pump fuel is a false economy in the long run. It certainly was in Okie's case. :ugg:

 

[nikki]

OMG... I understood one of Rich's posts... someone please call a doctor! ;)


Thanks for the explaination, Rich! Can't wait to explain it to Red tonight...

 

[Rich Rohrich]

Originally posted by nikki
OMG... I understood one of Rich's posts...

:eek: :scream: :yeehaw:

 

[Danman]

Dr. Dave Redszus the blender of FirePower race fuels gave me these numbers as typical distillation temperature values at the refinery for Northern Illinois in the summer.
10% - 158
50% - 250
90% - 374
End point - 437

while Phillips B35 looks like this consistently

10% - 156
50% - 204
90% - 217
End point - 250

I take it that these are % of fuel vaperized at a certain tempature? So at 250 degrees 100% of the B35 is vaporized as opposed to the 437 on pump gas?

 

[Rich Rohrich]

Originally posted by Danman
I take it that these are % of fuel vaperized at a certain tempature? So at 250 degrees 100% of the B35 is vaporized as opposed to the 437 on pump gas?

You just passed Fuel Tech 101 Dan. :thumb:

 

[jmics19067]

sorry Nikki,

I could of had you chasing a non problem the wrong way. Could of been real expensive to change rings and lean jets only to get pinging. Am extremely glad Rich stepped in and straightened out the fuel issue

I can say with some degree of certainty that if any unburnt fuel gets past the rings your oil will turn black quickly and if it smells like gas it was in there way to long. Ever noticed new cars can go 3 thousand miles with the oil still looking like honey and yet the old truck or lawn mower gets black as soon as you start it up. For whatever reason a lot of that is because unburnt fuel is getting past the rings,also the same reason why propane engines stay clear. So with maybe 5 % of the driveway test of sniffing your dipstick :eek: and 95% of the knowledge Rich shared........ :)

 

[Rich Rohrich]

Keep in mind the situation only gets worse as the rings wear and blowby increases. These bikes DEMAND regular preventative maintenance because they wear parts out in a hurry.

Don't discount the possibility of rings being worn if the hours are high enough.

 

[Danman]

Thanks for clearing that up.