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Metho in the petrol tank

Discussion in 'Bling and Appearance' started by BlueRex, Oct 2, 2007.

  1. The maintenance guy in the building i work rides a sr500 and has been riding for years. He suggested once a month i put 2 caps of Metho in the fuel tank to get rid of any water.....

  2. This is an old bush trick, I guess it depends on the quality of the fuel you're getting as to whether or not water in your fuel is an issue. It won't hurt anything though.
  3. From a scientific point of view, this is a valid idea. Ethanol is hygroscopic, so much so in fact that you can't distill it past the azeotrope of about 96%. This is usually the concentration of metho. If you wanted it to work even better, you could dessicate the metho over concentrated sulfuric acid for a day (other dessicators probably wont work) to dry out the remaining 4% water.

    Obviously you don't actually need to do this, its just something I would do cause I'm a nerd. Go for it, its a great idea and as long as you put it in after filling the tank up with fuel so as not to dilute the petrol too much, there should be no problems. I might even do this myself, thanks for the tip.
  4. Haven't heard that one before but it certainly makes sense. Metho will absorb the water.

    Yeah, what he said. :LOL:
  5. Far better to just stop the water building up in the tank in the first place (ie don't leave the bike sitting for ages). Metho will disperse the water in the fuel but then when it gets to the carbs/inlet manifold that water turns to steam - which is highly corrosive to some metals (why ethanol blended fuels aren't recommended for a lot of engines).
  6. Works a treat.

    I had water in my lawn mower's tank and I couldn't get it started, I had to remove the plug and wipe it dry.

    I put a bit of metho in the tank, filled it with petrol, ripped away at the starter and it fired.
  7. Yes, but don't use more than 1 cap per tank, and don't do it on a regular basis, as the water/ethanol mix can corrode metal and damage plastic/rubber parts. Also, if you have not got any water in the tank the metho will absorb it from the atmosphere and cause rust in the tank. Also you may need to change your fuel filter if its a paper type, as the water/metho mix can cause swelling of the paper fibres and block the filter.
  8. Snowball, do you think you have a water in fuel problem?

    Water could come from condensation on the inside of the tank (especially if the bike has been standing partially full overnight or longer) or from crap fuel... are either of these relevant?

    Metho does work a treat - don't go overboard though! A couple of other things you can do though in lieu are:

    Every now and then on the freeway, flip to reserve. This will ensure you don't have water and crap building up too much in the tank (if your bike is prone to that sort of thing) since water will collect at the lowest point - which is roughly where your reserve take off is. Don't do this if you think you have a serious heal of water though! Better to disperse as discussed.

    Or if you have extra time and TLC attitude, remove tank and drain into a bucket, rinse and repeat... while you're at it check and/or replace the filter at the same time.

    If you often run down to reserve anyway, just keep on keeping on. You're already cleaning up the low point every now and then as it stands.
  9. Thanks Rob, not sure why he suggested it i don't think i do have any water in the tank and i have not had any problems so i will as you suggest.
  10. The water only turns to steam in the combustion process, not in the carb or inlet manifold. This is not a dangerous process in itself - it occurs every day in every engine due to the water vapour in the atmosphere.

    That is why you see water dripping from the tailpipes of cars, especially, on a cold day, and why vehicles which are only used for a few kilometeres of travel end up rusting out the exhaust system or muffler(s).

    Once the entire exhaust system is warm enough the moisture in the exhaust can no longer condense inside the exhaust system itself and is emitted as invisible water vapour.

    Ethanol is more of a problem for rubber components in the fuel system, than for metal ones.


    Trevor G
  11. The recommendation is to use one or two CAPFULs per tank, not a cup full!

    At that low concentration the filters have no idea that there is any "alcohol" near them!


    Trevor G
  12. Actually, the reason you see water dripping from the exhausts isn't really to do with the water in the atmosphere, although some of it is.

    Octane is one of the major parts of petrol - C8H18

    Combustion of octane is:

    2C8H18 + 25O2 -> 16CO2 + 18H2O

    So burning petrol produces water, and it condenses in the tail pipe until it is, as you said, warm enough that it doesn't even do that. Water vapour in the engine is to be expected, it's part of the chemical process.
  13. Trevor / Ginji... I was waiting for someone to pick up that point... I didn't want to be accused of picking on JD.

    JD might be right IF carby's do get hot enough to turn tank condensation into steam... but this is not something I've seen in my common experience.

    Otherwise, he wasn't precluding the fact that a by product of combustion is indeed water vapour.

    Well spotted fellers.

  14. The best way to keep water from your tank, is to keep a 20 litre drum of fuel at home, and fill your bike to the brim after your ride. No air in the tank means that condensation won't happen. Takes self-discipline, I know, but you can do it if you love your bike.
  15. Hmmm...I'm glad you included water vapour in the atmosphere, because I see water vapour from diesels now. I didn't realise it occurred with diesels - I assumed the combustion was so much better with the higher compression ratio that water vapour could not condense. However my old Mazda Capella with the awful Pressure Wave Supercharged engine would pump out globules of water on a cold start.

    Diesel doesn't have C8H18 does it?

    The amount of C8H18 in petrol also would not be enough, surely, to produce the copious amounts of water vapour seen emitting?

    Especially with around a 12:1 ratio of air to petrol?


    Trevor G

    PS Thanks for the tech info :)
  16. The old aviation trick of filling the tanks overnight. I can handle a bit of water in my bikes tank but not my plane!! :wink:
  17. Oh ta, yeah spelling edited. Cap for car-size tank, cup for bike...DAMN I did it again... Cup for car-size tank, cap for bike... that's better
  18. If it did that I reckon you'd have a problem. On combustion petrol increases in volume by around 150 times, turning water to steam however gives a volume increase of 1600 times. Your also forgetting that the inlet manifold is operating at less than atmospheric pressure - which significantly reduces the boiling point of water. By the time it gets to the cylinder most of it would already be steam - otherwise you'd be noticing the affects of the increased pressure (like blown head gaskets).
    As Ginji pointed out the water from the exhaust is a product of combustion, and obviously any condensation formed in the pipe from sitting.
  19. If you take the previous formula for combustion of octane, and burn 2 moles of octane (which weighs 228g, and is about 325mL), you product 18 moles of water (which weighs about 324g and is about 324mL) So it's almost a 1:1 ratio of octane to water produced by volume.

    So yes, the combustion process produces enough water to account for what you see. Most of it remains as a vapour, and doesn't condense.

    As for diesels, the same sort of combustion formula applies. It takes in the fuel (generally taken as C12H23), burns with oxygen and produces CO2 and water. And as with petrol engines, some of that water condenses in exhaust and you see it.
  20. One of the products of combustion with any HC fuel is water vapour.

    I have a carby bike. Fuel goes from tank to the bowl, metered out into the carby and then to cylinder via inlet valve. The temperature gauge says 84degC, so assuming the whole carby gets to this temperature, any water in the bowl still isn't likely to turn to steam. The question is, will it turn to steam in the carby or just after or not at all?

    Actually I'm doubtful that metho dispersed water is going to turn to steam anywhere before combustion - I spose a check of steam tables (which I don't have right now) might give some better clues about the probability... if you can guess the pressure in the bit between the carby and the inlet valve...

    I agree it would be advantageous for the water to vapourise, but it's not really an issue.

    If in the worst case water doesn't vapourise before hitting the cylinder/combustion process, then I'm thinking the little amount of water in the atomised fuel spray (assuming water has been well dispersed throughout the fuel by the metho) that survives freezing as it passes through the venturi, is hardly likely to kill the combustion chamber due to volume expansion...

    I used to be student pilot. I've experienced carby ice and applied carby heat to melt the ice. The understanding is that actual droplets of water then end up passing into the combustion process turning to steam and being exhausted. Not an issue. The plane flew happily and safely and has since.