So I have ordered a Mikuni VM38 carb kit. Today was prep day and I noticed something startling, the gas in my carburetor was a reddish / brown color (similar to a nice ale). I drained some gas from the tank into a cup and noticed a similar hue, but not as "deep" as the gas sitting in the carb for a couple days.

Some background: The tank had been sitting for 30 years with gas, was completely rusted out inside. Had a radiator shop treat it with Red Coat a month ago.

Should I go back to the radiator shop and ask for it to get redone? Is this normal for a redcoat sealed tank to produce reddish gas? There are no particles at all in the gas as witnessed from emptying both the float bowl and letting out about a cup of gas from the petcock.

EDIT: Also, I should add that the cup I was pouring the gas into was transparent green, would this explain it?

 

I have had a few tanks treated with RedKote and have never had a problem. I would look at the gas in a clear glass [not plastic] jar. And compare it with some fresh gas.

 

This is a picture of the gas in a clear glass mason jar. The color is very close (use the white as a reference). This makes me cringe... I have only run about 35 miles since firing it up, but its been from this same tank. Don't have any fresh gas around to compare, but the only fuel I have seen this color is off road diesel. EDIT: According to the Redkote information PDF I found, gas that contains more than 10% methanol will leach the red dye from the coat, with apparently no effect on the tank/coating or engine.

 

As long as there is no sediment in the fuel, I would not be too concerned about the color.
You are probably too young to remember Gulf Oil's premium Crest gasoline back in the late 1950's, but it was colored purple!
Ditto for Royal Triton motor oil.
If the bike runs good the fuel is fine.

If you are still concerned about the color do this:
Buy a gallon of new fuel in a lawnmower can.
Pour a cup full of new fuel in a cup and note the color and set it aside.

Next, drain all of the fuel out of your tank.
Pour in the gallon of new fuel and let it sit for a day or two in the tank.
Drain a cup full of fuel out of the tank into a cup.
Are both cups the same color or is the cup out of the tank redder than the cup out of the lawnmower can?

If the tank fuel is redder, then there is some leaching going on.
In that case I would take it back to the guy who did the coating....... or just buy a brand new tank for a hundred bucks and some change and get it painted.
pg

 

I am very attached to the tank as it is a '78 original with lettering (and AMF logo) in excellent condition, they did a good job keeping it clean at the radiator shop too. Considering that the fuel I buy is 10% ethanol I am leaning on the leaching of color. Gotta find some better gas.

 

If it is just leaching the color out you could fill the tank, let it sit for a few days, drain it and repeat. If it's just the dye coming out then there can only be so much there, eventually color should stop coming out of the coating but you'll definetly want to watch it and make sure the actually coating on the inside of the tank is sticking still.