Project My Fizzer

Gentlemen
Every day we learn a bit more but still don't seem to get the final result. Have no idea how many sites, downloads, and so on and still at an impasse.
Let's look outside the square. I propose an email or letter to Yamaha Australia explaining our dilemma and seek some assistance. We have on this forum many fzr250 owners and we have searched for some basic answers and would very much appreciate some assistance from the parent company so that we can move on. What is the worse that can happen, they say that they are unable to help????
What do you good people think?

 

OK in the name of science I did an experiment today, I still haven't attached my tank, so I used my little fuel reservoir to run the bike for a bit.

I had maybe 150mls in the can and raised it up high and inverted it completely.

Guess what happened - I got the chugging problem. Immediately I lowered the fuel can below the level of the carbs and kept the machine running, after a few minutes it came back to life. The whole time I had it at full throttle just to keep it running.

So I'm hypothesising that after a high speed run, or if the machine has been sitting overnight with the fuel tap turned on the carbs are overfilling, maybe not to the point of leaking down into the cylinders, but enough that it just won't run properly.

So start your machine, with the fuel tap turned off, and see if it's running properly, if it is, get going before turning the fuel tap back on and go for a 100 or so metres before turning the tap back on.

It might be a good idea t run it for a minute of so with the tap off at the end of a ride also.

Do you turn the fuel tap off each night?

If not try turning the fuel tap off before killing the engine after a ride.
Then when you next start it next time, get it running before turning the fuel tap on.

This points to suspect needle and seat valves

peace out

Glenn

 

Guys just one observation, I think that looking at other different capacity bikes and seeing the fuel height different is confusing you.

The reason that I think this is because there's so many other factors that are going to govern the fuel heights on those bikes. The strength of the intake pulse, jet sizes, emulsion tube sizes, jet needles etc etc etc.

Consider that the 250 is a tiny little engine, with short sharp intake pulses, that go higher in frequency than all of the other bikes, in some cases by as much as almost 100%, so what seems to be a high fuel level may be needed to actually get the fuel into the engine in such a short space of time.

This is just speculation on my part, but what we need is a fuel height and way to measure it. i know what mine was, but will double check it today.

I'll have my tank attached today, with fuel in it and hopefully rego today or tomorrow.
So I'll check my fuel heights, take it for a run and do some plug chops in the coming days and see what's what as far as fuel/air ratio.
I'll carry tools to check fuel height, so that is at any stage it goes weird on me, I'll shut off the fuel and check each carb to see if it's gone high.

Bear in mind that I don't have a fuel pump fitted, which may be a good thing as it's one variable less to consider and from my test yesterday, even a slight change in fuel pressure seemed to be sufficient to cause problems.

I'm also pondering if the fuel pump giving too much pressure may be causing issues.
1.5 psi is minute pressure, perhaps old needle and seat valves and too much pressure is all it takes to cause issues.

peace out

Glenn

 

Guys I'm not the messiah, however I used to be a very very naughty boy.
But I feel I have a message worth sharing unrelated to Christmas...

Got my tank attached this afternoon and fired the fizzer up. I put 5 litres into the tank.

Remember I don't have a fuel pump, so it's only gravity feeding the fuel pressure to my carbs.

First I turned on the tap for about 10 seconds then off again. Running fine I left it to warm up, while I moved a car, then I turned the fuel tap on, revved it a few times and bingo it started chugging.

So I immediately turned the tap off and held the throttle full open for about 2-3 minutes till it started running properly.

Rode it 50 metres down the street with the tap still off, came to a stop, turned the tap on and didn't even get to start the u-turn before it started chugging again. So same routine, wait 2-3 minutes, throttle pinned wide open till it came good again.

I repeated the process again same result, the second time however the engine started backfiring after coming good again, so I've left it to dry out before pulling the carbs off.

Now the search for reasonably priced needle and seat valves and I'm also going to re-check my floats once I've got the carbs off

peace out

Glenn

 

let us know when you find them at a good price, where/how much would be good information to keep on the forum