Pre-mix separating??

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Jul 31, 2003
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#1
Tried searching but not much luck, so....

Recenly made the switch to Chevron avgas 100LL. I mix at 32:1 with Maxima 927. Bike is a 98 yz250.

I drined the tank and carb bowl before adding the new fuel. After adding the new fuel I only had a chance to ride it for about 5 - 10 minutes in a small field next to my house, but the bike ran great.

A couple days later I start it up and am warming it up and it dies after maybe 2 or 3 minutes. It will not start back up. Plug is not fouled, but changed it anyway. Still could not get it to start.

So today at lunch I notice that there was a drip at the bottom of the carb bowl. When I wiped it, it felt just like pre-mix. I didn't have time to investigate further.

But this has me wondering if the pre-mix could have separated that much in just a couple days? Is this common with Chevron avgas 100LL, it never happend with pump gas?
 
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#2
forgot to mention that because of the drip of what appeared to be pre-mix at the bottom of the carb bowl. This makes me think that the premix settled at the bottom of the tank. So when i started it the next time, it ran the fuel out of the carb and then got almost pure premix from the tank.

Can that happen?
 

Y2Z

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#3
im not sure about that particuar oil but when my KDX sits there for months at a time, it starts fine and there is no symptoms of it running rich. even if that could happen(mabe it can i dont know) i doubt it would do it over a few days.
 
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#4
doh!

After reading the label on the bottle of 927, I see that it states that separation can occur if the temp drops below 35 degrees F with some racing fuels. Guess Chevron Avgas 100LL would qualify and that is what happened.
 

Y2Z

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#5
that would make sense for my kdx too because my bikes are always in a heated area, but is that only with that 927 stuff??
 

Studboy

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#6
Castor oil is prone to separation at lower temperatures.
 

SPR

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#7
Yes Castor oils do tend to seperate in cold temps. Try to only mix up what you need to ride each time and drain the tank / carb after each ride back into your gas can. Next time you ride shake it up, pour in and roost.

The other option is to get your bike into the 21st century and use syntheitc 2 stoke oil. No separation, clean burning and less maintanance but it don't smell as good as Castor :-)
 
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#8
yeah, I called Maxima to ask about this. Their tech. guy suggested switching to synthetic and I won't have this problem. Probably good advise.