Just got XZ 550

[fret not]

Is the float valve functioning ?  It needs to open to allow fuel into the carburetor. 

I would begin at the carburetor and work back along the fuel line looking for blockage.  The fuel line to the carbs is shaped like a "T", and that might be the first place to look, as it comes in one line from the fuel pump and splits at the "T" to each carb.  Since fuel is getting to the one carb fuel must be getting to the "T".  It is a very short distance from the "T" to each carb.  This causes me to think there is a blockage in one side of the "T"  or the float valve is not functioning properly. 

[Slav91]

I bet its the float valve, because I have clean the carburators  + the gas is new just from petrol station in clean bottle. I must adjust the float level so that they close right in time and gotta check it are they even working. I had similar isue couple months ago, when my pilot tank was high they overflow from each choke.  ???
But does anyone know how to adjust float bowl?

[fret not]

Adjust the fuel level in the float bowl by bending that little metal tab on the float you were asking about previously. 

[Slav91]

Any measurements or just on felling?

[QBS]

Use the clear tubing you already have attached to the float bowl overflow spigots to measure the fuel level inside each bowl.  The fuel level should be at about the same level as the float bowl gasket.  The measurement should be made with the carbs level.  In your picture the left hand carb appears to be set at the approximately correct level.  There is some speculation within the V community regarding drivability improvements/changes related to higher or lower fuel levels. Perhaps another V member can provide more specifics.  Setting the float bowl fuel levels is described in the Haynes manual.

[The Prophet of Doom]

+1 on the clear tubing, but I think the level is 20mm below the gasket.  Check the manual to be sure.
It's most probably the float valve - you can replace the o-ring with a standard viton (fuel safe) one - it's a standard metric size. If the valve is corroded, some metal polish may help shine it up so it will seat better


Setting your float bowl levels correctly is critical for good performance

[Slav91]

I have change the o-rings on both float valves, they are oil and gas resistant. I'm gona disassemble the tops again and see if there is a problem with how float valve sits and shut down the fuel. Maybe one of the problems is how float bowl push the valves. I have reajust that part on float bowl what push the valve, because couple of months ago I had gas leaking in both carburator choke overflows. Gues I did it wrong.  :-X

[The Prophet of Doom]

I had gas leaking in both carburator choke overflows. Gues I did it wrong.  :-X

Unfortunately Yes, i think overflowing on one and no fuel at all in the other is not so much of an improvement  :( .
If you look at Haynes it shows a way of rough checking the float by measuring with the top removed and inverted, the gap between the gasket and the float.  This can save a lot of time, but gets you close only.  The only way to get it right is thee way you measured.


When I was doing mine I put some hose where the T piece goes and blew into it.  Even closed I could blow!   That was when I realised there was corrosion in the float valve seat letting fuel through when closed.
The same will help you find your blockage I think on the other carb.

[Slav91]

I did have circle on one of the valves  ??? at least now I know where to look for problems. Thanks :D

[Slav91]

Got allot of work at my job so didn't have much time working on the bike. Anyway at free time I got fuel level all good in both carbs and then I assemble it, bench test it it was all good until i put it back on the bike and this time it didn't overflow on overflow holes.  I don't know how but the air inlet of front carb  got full of fuel (over the brass plate) I got it all clean so It didn't go into cylinder(it was air tight) when i put the gas on and off the fuel got into the cylinder again it was filling the venturi with fuel on some level then it stoped.  Does anyone have an idea where to look? The good thing both sparks on cyl have fuel on them, so one problem is fixed but got the other one now.   :D

[Rikugun]

An interesting dilemma indeed. If fuel did not flow from the carb overflow tubes I'll assume the engine did not fill with fuel through the carbs. I have a possible solution but it requires more assumptions.  :)

I'll assume your petcock is a vacuum type and the vacuum line that feeds it comes from the front cylinder. I'll then assume the diaphragm in the petcock has a hole or tear. I'm imagining fuel flowing through the tear or hole to the wrong side of the diaphragm into the vacuum line then into the front cylinder's intake manifold. The final assumption involves the intake valve being closed and functionally sealing well which then causes the gas to back up the manifold and fill the carb's venturi from below.

[QBS]

Not sure, but the routeing of the clear hose to the black spigot looks suspect.

[Rikugun]

QBS - you don't like my highly speculative and unlikely scenario!?  :)

While not original, the clear hose appears to be connected properly to the pressure regulator. Someone with a spare set handy might verify though.

[QBS]

Rik, I'm just happy to see you back here again.  Good man.

[Rikugun]

Thank you QBS, I appreciate that.  :)

[The Prophet of Doom]

I hadn't noticed he'd been gone.  Did you get banned Rikugun?

[Rikugun]

Oh Rohan, don't be so coy. Have you forgotten the heartfelt letters we exchanged on a weekly basis?   ;) OOPS! Oh dear, it's out in the open now.... Well, I don't think your girlfriend reads the forum - you're probably safe.

And no, I wasn't banned. That would have been one for the record books based on duration though. While I've only come close to joining the "Banned Club", there is always the future. Save me a space.

[Slav91]

I have tried to start it. Now the good news is that smoke is coming from both exaust and there is no bang like it use to be. As for gasoline problem it has disapear, the petcock is not original nor it is vacun operated it is just simple "open" and "close" valve with electrical valve (when you prime the bike it lets gas flow, but that is dissabled). My gues it stayed to much  time on "open" side so it overflow on some way. Now when I give throtle when I try to start it it had some life in it (like its about to start) but no luck. And it hapened that it throws air from front carb I think. How should i put the fuel mix screw? Maybe it doesn't get any fuel on hole under the brass plate?  ???

[Slav91]

Well the bike is haunted. I have started it without radiator. But with choke and throtle on, without it it goes dead. And it did work but as soon i let the start button it stops. Its 15 seconds on the end of the video. Nevermind my happines  :D

http://vid270.photobucket.com/albums/jj92/Felony-14/Yamaha%20XZ550%20bobber/20160508_190335.mp4

And this is the second time with radiator and cooling. No luck, it tries to start but there are fire coming from the carburators of  front cyl.  :(

http://vid270.photobucket.com/albums/jj92/Felony-14/Yamaha%20XZ550%20bobber/Nov.mp4

[Slav91]

Here are the shorted videos.  :D

When it started(it doesn't sound right)

https://www.youtube.com/watch?v=JJ5Yb62xCwg

And after i assembled the radiator and put coolant.

https://www.youtube.com/watch?v=1mYbwz6f6-E