Help, Gas coming out of Airbox?

[crazy steve]

The 79 SF did not have those screens in them in the US, those are specific for the 80 model and up carbs...

Those float valve filters were OEM to all the XS11 carbs, but tended to disappear if somebody has been at the carbs...

[unicorncomputer]

Is there a special way to remove them and move them to the new valves?

Thank you,

Steve

Those float valve filters were OEM to all the XS11 carbs, but tended to disappear if somebody has been at the carbs...

[unicorncomputer]

They are brass floats. Thank you for the suggestions of the white paper.

Just for my knowledge, why does the water have to be hot?

Thanks,

Steve

Put a piece of white printer paper on the cardboard b/c the gas might evaporate if its a slow leak and you might not see it...if you put a piece of white paper it might stain it.

To check you floats (I assume they are brass) fully submerge them in in water that is about 120 degrees or so (as not to burn yourself) and if there is a hole in it it will blow bubbles as the air expands in them, if it doesn't have gas in it already. If they are plastic then this approach wont work b/c I believe they are solid...

Check the tech tips on setting float height, let us know if you have brass or plastic as the setting is a little different from what Ive read...

[DGXSER]

Hot water makes for hot brass, which then heats the air inside the float. Hot air takes up more room than cold air, or it develops pressure.

When you put the float in hot water, the air inside the float will increase the pressure inside as it heats up wanting to come out of the float. If it has a path to escape, you get bubbles. Where air can come out, fuel can go in.

As far as the filters on the float needle valve seats, they are a snap on fit. You just have to gently pry them off.

[unicorncomputer]

Thank you for that explanation.

Steve

Hot water makes for hot brass, which then heats the air inside the float. Hot air takes up more room than cold air, or it develops pressure.

When you put the float in hot water, the air inside the float will increase the pressure inside as it heats up wanting to come out of the float. If it has a path to escape, you get bubbles. Where air can come out, fuel can go in.

As far as the filters on the float needle valve seats, they are a snap on fit. You just have to gently pry them off.

[natemoen]

I would use hotter water, boil the water and then dip the float in it after taking it off the stove.

[unicorncomputer]

Carbs are off, Floats are brass. I held each on beneath water hotter than I can withstand using needle nose pliers for about 15 sec. each. No bubbles.

I did replace the valves and needles.

When measuring from top of float to lip that gasket sits in, 2 of them read 27 and 2 read 28.

Which setting is correct or are they close enough?

When I took tank off and set it on saw horses with petcocks in the off position, I did have one that started dripping. Guess I will be stopping by Ronnies Cycles tomorrow to see if they have a rebuild kit for it.

Thank you again for all your insights,

Steve

Hot water makes for hot brass, which then heats the air inside the float. Hot air takes up more room than cold air, or it develops pressure.

When you put the float in hot water, the air inside the float will increase the pressure inside as it heats up wanting to come out of the float. If it has a path to escape, you get bubbles. Where air can come out, fuel can go in.

As far as the filters on the float needle valve seats, they are a snap on fit. You just have to gently pry them off.

[mikubuilder]

the height should be about 25mm for brass floats +/- 1mm(so, about an inch)

[WMarshy]

Carbs are off, Floats are brass. I held each on beneath water hotter than I can withstand using needle nose pliers for about 15 sec. each. No bubbles.

I did replace the valves and needles.

When measuring from top of float to lip that gasket sits in, 2 of them read 27 and 2 read 28.

Which setting is correct or are they close enough?

When I took tank off and set it on saw horses with petcocks in the off position, I did have one that started dripping. Guess I will be stopping by Ronnies Cycles tomorrow to see if they have a rebuild kit for it.

Thank you again for all your insights,

Steve

You should have one vacuum operated fuel valve which we call an octy because it has so many hoses coming in and out of it. That octy has a diaphragm in it that needs replacing also not just the seals and stuff in the petcocks. Some owners remove them though, the trick is knowing if you have one or not.

[unicorncomputer]

Someone had removed the OCTY before I got the bike. I am in the search for one to put back on the bike, but haven't located one that is affordable yet.

If you know of one, please let me know.

Thank you,

Steve

You should have one vacuum operated fuel valve which we call an octy because it has so many hoses coming in and out of it. That octy has a diaphragm in it that needs replacing also not just the seals and stuff in the petcocks. Some owners remove them though, the trick is knowing if you have one or not.

[natemoen]

the height should be about 25mm for brass floats +/- 1mm(so, about an inch)

That is 25.7mm +/- 1 mm

[CaptonZap]

What were you main jet sizes? If they were 115 or 120 then they are the 80-81 style...



I could swear the screens were only on the '80 and up models...

The 3 banks I've been in were a '79 F, SF and a '78 and neither had the screens.

Could be, as somewhere in the many XS parts vendors sites I've seen on the web, I saw the screens advertised as a seperate component. They could have been added to the carbs I have, but it would seem logical that Yamaha would put them on at the factory. Dunno. CZ

[CaptonZap]

When I took tank off and set it on saw horses with petcocks in the off position, I did have one that started dripping. Guess I will be stopping by Ronnies Cycles tomorrow to see if they have a rebuild kit for it.

Thank you again for all your insights,

Steve

I just had a petcock that seeped a drop or two an hour. So I took off the cover with the vacuum port and the two diaphrams with the spacer block, and inside there is a o-ring on the center post that makes the seal. The seat it rides on looked good, so I went to the seal store, and bought some Viton o-rings, 2mm thick by 4mm ID. Put one on, and that cured the seep. 6 o-rings for $5.
CZ

[unicorncomputer]

I just took the petcock apart, but I don't see the spring like people have shown or talked about. The gaskets all look good - I will be brining it by the local shop for inspection.

Thank you.

I just had a petcock that seeped a drop or two an hour. So I took off the cover with the vacuum port and the two diaphrams with the spacer block, and inside there is a o-ring on the center post that makes the seal. The seat it rides on looked good, so I went to the seal store, and bought some Viton o-rings, 2mm thick by 4mm ID. Put one on, and that cured the seep. 6 o-rings for $5.
CZ

[natemoen]

That's cause you have a special, and specials don't have that in the petcocks, they only have that in the octy.