yamaha 2.5hp 4 stroke warm start issue

[BelleSerene]

The best approach is, indeed, to drain the float bowl using the drain fitted, when you leave the engine for more than an week or two. This does clear out the crud before it becomes a problem and ensures 100% drain out which running the engine cannot achieve. I have permanently attached a short length of fuel hose to my 2.5 which pokes out of the casing just below the power head to make it easy to run the petrol out into a small bottle.

Interesting, Richard. So do you turn off the fuel supply using the lever on the outside of the engine, then lift the cover and open the carb drain screw to empty the carb, then tighten the screw? And do you put the fuel back into a fuel can/ the fuel tank (perhaps through a water separator), or dispose of it?

 

[RichardtheBoffin]

Interesting, Richard. So do you turn off the fuel supply using the lever on the outside of the engine, then lift the cover and open the carb drain screw to empty the carb, then tighten the screw? And do you put the fuel back into a fuel can/ the fuel tank (perhaps through a water separator), or dispose of it?

Yes, that's what I was thinking. I would never put it back into the fuel tank as it will just accumulate the crud.

Adding the pipe to the drain means removing the drain screw and fitting something suitable to the end of the extra pipe. You'd need to be sure the pipe was secure on the carb of course.

I am suspicious about how the particles got into the bowl as there is a filter in the fuel tank which looks quite fine.

I bought some very fine mesh stainless which I might make into a filter to install after the fuel tap just before the fuel gets to the bowl.

On another engine, I found a jelly like gunk in the carb bowls and I believe that this came from the glue used in the fuel pipes to bond the inner and outer layers over the thread re-enforcement. I tested a small piece of pipe in a jar of petrol and it dissolved the glue and you could separate the pipe into it's component parts! Not good!

I read a lot of bad things about what modern petrol does to things due to the high ethanol content...

 

[RichardS]

Interesting, Richard. So do you turn off the fuel supply using the lever on the outside of the engine, then lift the cover and open the carb drain screw to empty the carb, then tighten the screw? And do you put the fuel back into a fuel can/ the fuel tank (perhaps through a water separator), or dispose of it?

Obviously designs will vary but my DF2.5 has a small nozzle thing on the bottom of the carb float chamber which is opened by turning a screw so that the fuel runs out of the nozzle. I pushed a few inches of fuel pipe onto the nozzle and led that out through a small hole below it and off to the side a bit. There is a hole in the casing directly opposite the screw so one can push in a screwdriver to turn the screw.

I assume the original idea is that the fuel runs out of the nozzle into the bottom of the casing and then finds it's way out through the hole .... but that's all a bit hit and miss and petrol ends up everywhere so the short length of pipe is a big improvement because I can aim it right into the neck of a small bottle.

You can presumably drain the fuel out of the tank and through the float chamber and thereby drain the whole tank but I don't do that because it's very slow so I turn off the fuel tap and just tip up the engine and pour the fuel in the tank back into my petrol can. The contents of the float chamber are only 30 mls or so, so it's not a lot of fuel to chuck away anyway .... but what I do is either keep it and use it for cleaning engine parts or drain it into a small clean bottle and, if there are any particles in it, let it settle for an hour or two before pouring the clean stuff off the top back into the fuel can. That only leaves a ml or two in the bottom of the bottle for disposal.

Richard