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Discussion Starter · #1 ·
I have noticed a recent problem where my BMW R100 begins to blow white smoke out the exhaust after about 10 mins of riding. The engine will then begin to shut down..

I emptied the oil and noticed 2 things:
1. the consistency of the oil was very thin. Almost like water..
2. the oil smelled of gas..

I'm hoping someone can help me out in figuring out how gas is getting in the oil.

By the way, I did use the side stand for awhile but am now using center stand..

thanks!!
mnrider
 

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Has the bike been down? Also when did you last change the oil?
 

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Discussion Starter · #3 ·
I've owned the bike for about 4 yrs and it tipped over once about 3 yrs ago.

I changed the oil around April '09 with only about 300 miles of riding afterwards.
 

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Discussion Starter · #4 ·
Gee, it just occurred to me that as I was pushing the bike on to the stand, it tipped over. It wasn't a hard landing because I was able to keep it from doing so...

Is it possible for gas to get into the oil this way?

thx,
mnrider
 

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Anything with a carburetor can flood the sump with gas during a tip-over. It can also happen if a needle valve sticks open, such as the case with my Virago.
 

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Anything with a carburetor can flood the sump with gas during a tip-over.

It can also happen if a needle valve sticks open, such as the case with my Virago.
For fuel to "flood the sump", it would have to remain laying on it's side longer than a few seconds......and the "flood" should be limited to a couple of ounces......unless the bike continued to run.

The white smoke indicates a float or needle valve problem.
It should NOT be ridden that way because the fuel in the oil......and presumably running down the sides of the cylinder, will cause rapidly accelerated engine wear.
 

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Your petcock is your friend

Fuel in oil is a common occurrence on bikes w/ gravity fed fuel systems.
If you ever see the helmet sticker that reads "Turn on the gas, dummy", You also have to turn off the gas... Many times i've kicked my old sporty to life and just as you get into it you run out of fuel, at least in the carb bowl, and you start kicking all over again. But there is good reason to turn it off anytime you park it.

Bikes with non vacuum petcocks can leak fuel into the crankcase through the cylinders, past the rings. Taking with it even the highest quality motor oils and "gas washing" the cylinders leaving them uncoated, grinding metal on metal between the rings and cylinders.

Same thing applies to leaving your vacuum petcock in the prime (PRI) position.
In this position it is free to flow fuel through the carbs into the cylinders and on to the bottom end.

Floats and seats and needles are not reliable for stopping this condition.

Change the oil & filter & spark plugs, go for a good long ride and when you park it...Turn off the gas.

Hope this helps.
 

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This is a common problem with BMW airheads when they have aged a little.
Never leave the bike on the kickstand with the fuel taps open.
These bikes benefit from new needles. The range of activation of the float and sealing of the needle is much improved with new needles even when the old ones appear to be OK.
 

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Floats and seats and needles are not reliable for stopping this condition.
Ive never found vacuum petcocks to be to reliable either. Every single bike Ive owned with a vacuum petcock failed and flowed gas. Theyve been replaced with mechanical petcocks.
 
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