I realize this isn't a car question. There doesn't seem to be an appropriate Exchange for it, so I'm trying it here.

I have a two-stroke engine (for a rototiller), and it worked more-or-less well enough until it rained. It seems as if there might be water in the fuel. I tried filtering it with a brand new fuel filter specifically for removing water. Then I tried adding isopropyl alcohol, and some octane booster (as suggested elsewhere on the Internets). No luck.

It starts -- but won't keep running for more than a second -- if I put starter fluid in the choke with the air filter off.

I'm not sure what else to do. Any suggestions would be accepted with gratitude.

  • You're okay with regard to being on topic. From the FAQ: «Questions related to [...] internal combustion engines, even in applications other than automotive...»
    – jscs
    Commented Jun 9, 2013 at 18:45
  • If this is still open, what is the make/model/year of the motorcycle? Commented Dec 15, 2015 at 22:32

3 Answers 3


Is it possible that the fact that it rained is a coincidence? Could the fuel just be old? If you leave a two-stroke engine sitting too long with mixed fuel/oil in the tank, the mix will lose some of its lubricating properties---sometimes enough that when you try to start the engine it'll run for a moment, then overheat from lack of lubrication and stop. I would drain the tank as best you can and try putting in fresh fuel (with fresh two-stroke oil added in the proper ratio, of course).

  • Even if the rain is related and there's water in the fuel, draining the fuel is probably going to be necessary. Commented Jun 9, 2013 at 22:19
  • It's new gas and new oil. Like, a few weeks old.
    – Translunar
    Commented Jun 10, 2013 at 21:05

Fundamentally, any engine needs spark, compression and fuel in order to run. If it starts when you put starter fluid directly in the engine, that suggests to me it's not getting fuel.

If you've already filtered the water out of the fuel we ought to be able to rule that out. The next check is to make sure fuel is actually getting to the engine. How is it fed? Is it gravity, or is there a pump? Is there an in-line filter between the tank and the carb?

You may have an obstruction in the fuel line - if water could have got in, so could bits of grit, leaf, etc. Try disconnecting the fuel line from the engine (put the end into a clear bottle so the fuel doesn't go everywhere) and see if you can get fuel to flow. (there could also be a blockage in the carb, but try the easier stuff first...)


Water is heavier than gasoline and can usually be drained off of the bottom of the tank. If you are concerned about losing too much gas you can also dump the fuel into another container and let it the water settle out. You should be able to see a clear line between the water and the gas if it is present.

  • I filtered the fuel for water using a special filter for removing water from gasoline.
    – Translunar
    Commented Jun 10, 2013 at 21:06

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .