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Lowering the fuel level this way

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Lowering the fuel level this way

PostAuthor: Greenrider » Mon Feb 04, 2019 7:48 pm

I know this thread is 3 years old but has anyone else had any luck with lowering the fuel level this way viewtopic.php?f=6&t=55540 ?
I have been getting fuel drips at the accelerator plunger boot (it has a crack in it), and fuel in the crankcase (oil thin and smelling of petrol) so I removed and cleaned the carb and replaced the float needle valve and seat with aftermarket parts off eBay. Since this has not helped, I am attacking the float level.

I've been measuring with the bike level on a floor jack, running, after the carb has been primed (bowl filled), and let some fuel out of the drain tube into a container until the bubbles stopped coming then inverted the tube in a "U" shape and held it against the notch. The fuel level was initially parallel to the notch. I need it about 17mm below this mark according to spec. I bent the tang upwards and got the fuel level down about 5mm below the notch. This apparently is as far as it will go. I gradually bent the tang further in increments but the fuel level always remained the same or got higher!! At the end the tang was bent that far that it wasnt allowing fuel into the bowl at all. At this point I cooked my battery from all the engine cranking when priming the carb.

Any advice or ideas would be much appreciated..
Last edited by Jake on Mon Feb 11, 2019 1:15 pm, edited 1 time in total.
Reason: Posts split from a three year old topic

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Re: 2005 xv250 float level

PostAuthor: Greenrider » Tue Feb 05, 2019 4:27 pm

I also noticed how difficult it was to bend the tang. I had to get some pliers onto it as the metal seemed pretty strong and sturdy and impossible to bend with just my fingers. I was wondering under what circumstances the tang would bend out of spec on its own accord? How much pressure would be on it in its normal operating environment in the carburetor? Just seems like bending this piece of metal is compensating for something else because it obviously left the factory with the tang in spec.

Any ideas, thoughts or comments?

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Re: 2005 xv250 float level

PostAuthor: Greenrider » Mon Feb 11, 2019 1:28 am

An update here....

I've been at it for days carefully bending and adjusting the tang. It seems 10mm below the notch is as far down as I can take the fuel level otherwise the bike wont start. Whats the trick to it? Can anyone confirm that the XV250 manual saying "16.5mm-17.5mm" below the notch is not a typo? It just doesnt seem possible. What else should I be looking at?

Is 10mm below the notch acceptable? Im thinking of just leaving it, I think it has beaten me. The bike starts and runs fine but Im worried about the petrol smell that accumulates in the crankcase. Is it normal to smell some petrol in the crankcase?

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Re: 2005 xv250 float level

PostAuthor: Flyingdog » Mon Feb 11, 2019 4:07 am

Greenrider wrote:Is it normal to smell some petrol in the crankcase?


Absolutely not. Keep a very watchful eye on the oil level. If it rises even just a millimeter, start checking for reasons, "why". Of coarse a millimeter is an exaggeration, but there should "only" be oil in the crankcase.
Quick search thru 3 online manuals all state 16.5-17.5mm below piston valve center mark..so I would suspect it right.
Have you searched and compared? Also noticed the 535's highest level is 13.5mm. So it's a pretty safe bet your 10mm is too high for a 250 cuz of being 1/2 the size of 535 and demanding less A/F charge. Besides, being above a maximum level, is just that. Too high. Least, that's how I would see it. Are your float all plastic or combo of metal support and composite float pods. If bent, wonder if that could contribute to off measurements?
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Re: 2005 xv250 float level

PostAuthor: hypophthalmus » Mon Feb 11, 2019 12:58 pm

Perhaps the float valve is leaking?

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Re: 2005 xv250 float level

PostAuthor: hypophthalmus » Mon Feb 11, 2019 1:02 pm

Sounds a lot like this post, where that was the case: viewtopic.php?t=42302

Edit: whoops, should have kept reading. It was ultimately an obstruction in the carburetor / bent out of shape float..

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Re: Lowering the fuel level this way

PostAuthor: Greenrider » Tue Feb 12, 2019 1:31 am

Flyingdog wrote:Absolutely not.


When I initially change the oil the crankcase just smells like hot oil after the first run, after a few days it starts to get that sharp petrol tang about it. So this is obviously unacceptable. Ive been changing the oil once a week since noticing the petrol smell and its gone through 3 changes now. Im hoping it may be residual fuel dregs in the bottom of the crankcase that havent flushed yet? Initially I had a clapped out petcock that was running fuel (in the "on" position) even when the bike was switched off. Since rebuilding it, its doing its job nicely.

After rebuilding the petcock I also bought a new aftermarket valve and valve seat off eBay suspecting the old ones were to blame. With the bowl off, Ive checked that it only drips in the "prime" position and even then if I held the float up with my finger, the dripping stops. But when I crank the engine, fuel drips out of it but Im guessing that is normal.

The floats are both plastic attached to the metal bracket - stock issue as far as I can tell. Ive put them in water to see if they were leaking (blowing bubbles or sinking) and they seem pretty good. They dont look bent as far as I can tell.

I appreciate your input here guys because Im almost all out of ideas. Many thanks.

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Re: Lowering the fuel level this way

PostAuthor: Greenrider » Tue Feb 12, 2019 11:27 pm

Does anyone think it could be something else affecting the fuel levels? Perhaps the needle diaphragm is too old? (the bike is 20 this year). Or the pilot air jet blocked? I've pulled the carby apart about a month ago and cleaned it out, maybe I missed something or didn't put something back together properly? It was idling pretty rough this morning until I took it for a few kms. It's never been like this in the middle of winter and here we are now in the middle of summer! Would it be worth pulling the carb and going through it again? I'd rather avoid it if possible.

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Re: Lowering the fuel level this way

PostAuthor: Greenrider » Tue Feb 19, 2019 2:01 am

Pulled apart, cleaned, reassembled the carby and now I'm bench testing it. Hooked it up to the fuel tank sitting on the shelf above. I've noticed it leaks like a sieve when in "prime" after the bowl has been filled, is this normal? Or is a good valve needle and seat supposed to prevent this and stop fuel from entering the bowl?

When I turn the tap to "on" the fuel stops flowing. So the levels I'm reading are just where I stopped the flow of fuel and not the level where the needle and seat are stopping the fuel. Please help.

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Re: Lowering the fuel level this way

PostAuthor: Flyingdog » Tue Feb 19, 2019 3:30 am

Greenrider wrote: I've noticed it leaks like a sieve when in "prime" after the bowl has been filled, is this normal?


Of coarse that's not normal.

Greenrider wrote: Or is a good valve needle and seat supposed to prevent this and stop fuel from entering the bowl?


Of coarse it will. Are these new? If the float needle is deformed, hard or anything other than "perfect" condition...it will not shut the fuel flow "after" the bowls' fill.
If the seat is pitted, varnished, deformed in anyway...it will "not" stop the fuel flow "after" the bowls' fill.

Greenrider wrote:When I turn the tap to "on" the fuel stops flowing.


That's how a petcock works. When there is "no" vacuum put to it, the petcock will "Not" flow fuel when the bike is "not" running. That is if the petcock's internals are in good shape. When the bike "is running", vacuum is applied to the petcock, opening the diaphragm..letting the fuel flow to the carbs. If the float needle/seat is bad and the level is set too high, you're going to get flooding..specially idle'n. But, then again...if there's something wrong with the float's needle or seat and there's something wrong with the petcock's diaphragm you'll still get flooding even with the bike "off" and petcock is in just the "on" position.

Where is the leak? Is it the float bowl seam/gasket, inside the carb body, both?

To bad you didn't catch this earlier, hypophthalmus mentioned this over a week ago.

If you're fairly new to carb work, ya gotta be pretty methodical in dealing with carbs. Treat it like a paint-by-numbers set. A manual will tell ya all you need to know and when to do what..first..second...third and so on.
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Re: Lowering the fuel level this way

PostAuthor: Greenrider » Wed Feb 20, 2019 1:35 am

It's leaking from the carb body, down where the barrel meets the intake boot/manifold straight into the cylinders. Nice.

Buying a new needle and valve seat was the first thing I did. They weren't genuine Yamaha parts though apparently still made in Japan. Could they be faulty?

Rebuilding the petcock was the second thing I did with an All Balls reco kit. However on 2 separate occasions now I've noticed fuel still leaking out of it in the "on" position and the bike being off. But it's been fine on dozens of occasions.

This is only the 3rd time I've pulled apart and cleaned a carby so yeah fairly new to the joy of it.

Got the XV250 Workshop Manual when I got the bike 8 years ago. The manual is informative but doesn't have the problem solving skills that you knowledgeable folks have.

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Re: Lowering the fuel level this way

PostAuthor: Flyingdog » Sat Feb 23, 2019 2:37 am

Greenrider wrote:It's leaking from the carb body, down where the barrel meets the intake boot/manifold straight into the cylinders. Nice.


Don't know what to tell ya. Yes, something like this can be very frustrating. There's only one way for carbs to leak like this... fuel getting by the float needle. Less the carbs have open cracks, somewhere. Like the float seat towers or something. Only you can determine this as 'you' have the carbs infront of ya.

Greenrider wrote:Buying a new needle and valve seat was the first thing I did. They weren't genuine Yamaha parts though apparently still made in Japan. Could they be faulty?


Could happen, but even non-OEM parts should work. At least for awhile..specially being new. But like everything else, bad and/or faulty stuff does slip into the mix on occasion. Remember also, there's a copper (or whatever) sealing washer "under" the float seat. Parts can be left out, sometimes, by the builder. Guess the only thing here is to make sure the seat is clean and shiney. You can put a Q-tip in a drill, with a drop of polishing compound clean the float seat, just to be sure. And..of coarse the float needle's tip should be pliable. Also making sure the whole assembly moves freely on the floats' pivot pin.

Greenrider wrote:Rebuilding the petcock was the second thing I did with an All Balls reco kit. However on 2 separate occasions now I've noticed fuel still leaking out of it in the "on" position and the bike being off. But it's been fine on dozens of occasions.


Drip or two? While not totally disastrous, this is still wrong. There should be "No" fuel leaking past the petcock. Gotta be either the diaphragm and or mating surface. Possibly some pitting between the two materials. I couldn't tell ya why. Even if the petcock is still leaking, the floats' needle should shut the fuel off, in the bowls. Or visa-versa..the petcock "should" shut the fuel off before it gets to the bowls. There's just no other way about this.

And..above all, since you got all this "leaking" going on..be sure to check the crank case oil..fuel in the engine is not good.
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