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Motorcycle Repair/Draining 1973 Honda Gas Tank


Hi. I own a Honda 1973 CB175K and had it totally serviced by a motorcycle repair shop in October of 2012. I had very little gas put into the engine as I was going to be transporting it, which I did. I never turned over the engine or checked the new battery until the end of June 2013. (Bad, now I know.) That is when I just turned the key with button starter for a few seconds and the battery sounded slow but did turn over the engine using the button starter. I never even turned on the gas lever. I was told because I had left the small amount of gas in the tank for that long a period without starting the bike I should drain out the old gas and put in new gas. First, is it necessary to do this? After the mechanic gave me the reconditioned bike and drove it around several blocks and parking lots to show me how it worked I never started it again after he turned it off. I had the carb reset and cleaned, new gas lines and 2 gas filters attached, new battery and new clutch cable installed. My guess is they would have used the proper octane gas in it. If I do have to drain the gas I was looking under the bike and for the life of me I can't figure out what to do to get the gas out. Again, there is little gas in it but it is older gas. I intend to transport the bike again so I don't want to add a lot of gas to the tank to try it out and make sure it is running well. If I need to drain the tank please tell me the very easiest way to do that (ugh). If I don't have to drain the tank that would be wonderful but I don't want to clog up the carb or anything even though I have two gas filters installed. Please tell me what to do and how to do it if I need remove the gas. Thanks so much. Arlene

Hi Arlene,

I would try to get the old fuel drained as small engines and carbs are
not as tolerant as a car or truck would be to the old fuel.

The fuel passageways are smaller so there is a greater chance of the
fuel plugging things up.

Gas is not fun to mess with but there are a few ways of draining things.
The carb has a drain screw in the bottom of the float bowl to drain the
carb. You just loosen the screw a bit and the fuel should drain.

The tank can be drained by pulling the fuel hose off the carb
and running it into a container. If the hose is hard to
remove there is a sediment bowl on the fuel valve
that can be removed to drain fuel. It also has
a small screen up inside it. It seals with a rubber
o-ring so watch for that so it doesn't get lost.

The tank can be removed if you want to go that far and
dump it out.

Use a container to catch the old gas and dispose of it at
your local recycle yard or dump.

The tank should always have some fuel stabilizer
added to keep the fuel from going bad.
Any auto store should have that.
It only takes an ounce or less to treat the fuel
and prevent future problems.

Fuel can turn to a jelly like substance which plugs up
the tank and lines and carb so make sure
fuel flows out of the lines or the carb bowl
drain to make sure all is clear.

You can wear rubber gloves to protect yourself.

The easiest way might be to open the carb drain screw
and just let the fuel run out onto some absorbant
material.  Make sure the fuel tap is set on the
reserve position to fully drain the tank.

Let me know if you have more questions.

Wayne S

Motorcycle Repair

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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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