Fuel Line Check Valve??

[H2O]

Thought I was smelling gas each time we stopped during a 250 mi. ride last Saturday.

It also sounded really crappy at idle the more we rode.

Got back home and inspected it. Found a small diameter hose on the left side of the engine squirting fuel out whenever I turned the key on and the fuel pump ran.

There is a small plastic device in the line with an arrow pointing up. The rubber line is worn out and developed a small hole just at the top where this plastic thing is located and squirting fuel when the pump runs.

The line is coming straight down from something above the engine that I can see (but can't tell what it is) then going into this plastic "check valve" looking plastic device with an arrow pointing up, then into a slightly larger line, then into the front left cylinder.

 

I need to replace the fuel lines obviously, but what is this device? It has a smaller diameter on the top side then it does on the lower side where it feeds into the engine. I removed the hose and the device and can see through it so I'm assuming it's not a check valve.

What is it?

Edited April 21, 2015 by H2O

[cowpuc]

Wow H2,, what you are describing sounds familiar to me but not from a fuel line prospective.. The hose with the connector in it sounds like a vacuum hose that maybe runs from that front cylinder.. Can you show some quick pics or maybe look and see if it slips onto a brass connection into the rubber boot (intake manifold) directly under the carb that feeds that front cylinder? The gas situation actually sounds like a stuck float valve.. This would cause some really strange idling affect (like the bike is getting way over chocked/flooded). The only thing is, the overflow tubes run down the frame back bone and empty in front of the rear shock and should puddle on the ground...

[H2O]

I can do that later. Just got the bike back from having the carbs rebuilt too. Thanks!

[Prairiehammer]

Thought I was smelling gas each time we stopped during a 250 mi. ride last Saturday.

It also sounded really crappy at idle the more we rode.

Got back home and inspected it. Found a small diameter hose on the left side of the engine squirting fuel out whenever I turned the key on and the fuel pump ran.

There is a small plastic device in the line with an arrow pointing up. The rubber line is worn out and developed a small hole just at the top where this plastic thing is located and squirting fuel when the pump runs.

The line is coming straight down from something above the engine that I can see (but can't tell what it is) then going into this plastic "check valve" looking plastic device with an arrow pointing up, then into a slightly larger line, then into the front left cylinder.

 

I need to replace the fuel lines obviously, but what is this device? It has a smaller diameter on the top side then it does on the lower side where it feeds into the engine. I removed the hose and the device and can see through it so I'm assuming it's not a check valve.

What is it?

 

That plastic device is a dampener for the vacuum source for the boost sensor (vacuum advance).

There should be no fuel in that hose.

Perhaps, the fuel you see is actually coming out of one of the carb bowl drain hoses and running onto that vacuum hose?

Surely, the person who redid your carbs didn't mistakenly hook up that hose to one of the bowl drain hoses?

The bowl drain hoses should only have fuel coming out of them when the carb bowl drain valve is open or leaking.

[H2O]

Yes. Thanks for the photo.

That's the line and the device, and if I follow mine from the left front intake like yours is showing, it's going up to what I assume is the nipple pointing straight back down from the vacuum advance or boost sensor, and mine has the right side intake capped/plugged off just as you're showing in the photo which I also assume is for synching the carbs.

There was fuel spraying out at the top of this "dampener" from the worn out hose.

I'm assuming again that I have some sort of problem in the left front carb causing fuel to be coming out of a vacuum hose, right?

 

Just had the carbs rebuilt and before I could get home I had a fouled plug on the left front cylinder. The way it was sounding by the end of our ride Saturday I'd have to assume I've got another fouled plug.

[H2O]

If the float is sticking and I have to go into the carb, can I go through the vacuum chamber cover/cap to access the float, or will I have to disassemble the whole carb rack assembly?

[Prairiehammer]

If the float is sticking and I have to go into the carb, can I go through the vacuum chamber cover/cap to access the float, or will I have to disassemble the whole carb rack assembly?

 

No, there will be no access to the float chamber until you disassemble the carb. However, before you send the bike back to the shop that did the work, try tapping on the float bowl of the offending carb(s) with a plastic screwdriver handle or large wooden dowel, with the hopes that this action will jar the sticking float needle valve or hung up float.

 

If you are encountering fuel "spraying" from the vacuum dampener, you have a LOT of fuel being dumped into the intake of that cylinder. The risk of hydro lock is high, not to speak of the damage done as the cylinder wall is washed of its lubricating oil. Keep an eye on your crankcase oil level; the gasoline is likely accumulating in the crankcase and raising the oil level.

Edited April 22, 2015 by Prairiehammer

[H2O]

Holy S%#t! You're right, the oil level has raised over the maximum level line and it was fine before our ride Saturday!

I'm lucky I made it home without a major mishap, but at the same time I'm lucky that vacuum line failed!!

I'll try the "tap" trick but if I have to go into the carb(s) I'll need some direction.

I removed all the fairing, side panels, head light, cowl etc. before I took it to a local shop because I thought it would help them save time and me money.

Can I remove the side panel/air ducts and leave the radio and electronics in place, remove the air filter and air box then be able to get the carb assembly out through one side or the other, or will it be necessary to take all the fairing assembly off again?

I'm assuming I have to remove all the carburetors.....

[Prairiehammer]

Can I remove the side panel/air ducts and leave the radio and electronics in place, remove the air filter and air box then be able to get the carb assembly out through one side or the other, or will it be necessary to take all the fairing assembly off again?

I'm assuming I have to remove all the carburetors.....

 

IF carb removal is required, the main fairings (and everything within) can remain.

Remove the lower fairings (the "L" shaped cowlings in front of the rider's shins), the side covers and the aforementioned air box. The main fairings may remain in place. The four carbs are removed as a single unit through the left side.

But, to be frank, unless the 'technician' royally screwed up, you should be able to fix the leaking float valve without carburetor removal. It IS possible, though that he screwed up the carbs during reassembly or carelessly bent the float tab or failed to renew the valve seat O-ring or failed to replace the float valve needle or it could be something as simple as debris is caught under the float valve. This debris can come from the handling of the thirty year old fuel inlet hose, causing bits to slough off from within the hose. There is a "net filter" ( a fine metal mesh screen) at the inlet to each float valve that should have caught the largest pieces of debris, but it wouldn't take a large piece of debris to wedge the float valve open.

[H2O]

The debris is exactly what the shop thought may have happened to it.

The owner of the shop is supposedly reliable and he didn't want to use anything but genuine Yamaha carb kits and diaphragms, so I can somewhat assume he didn't screw the job up, but you never know unless you do it yourself I guess.

Do you think I should do some "tapping" on that carb then?

[Prairiehammer]

Do you think I should do some "tapping" on that carb then?

 

Definitely!

[H2O]

Okay, I'll replace the vacuum hose and the oil tomorrow evening, tap about on that carb and let you know how it turns out.

I really appreciate your time and advice.

If this all works out (or even if it doesn't) I'll buy you breakfast or dinner if you let me know the next time you're near here from upstate Illinois.

[Prairiehammer]

If this all works out (or even if it doesn't) I'll buy you breakfast or dinner if you let me know the next time you're near here from upstate Illinois.

 

Evansville? That's south of the Mason-Dixon Line isn't it? I'm not sure if I am allowed to return to the 'South' after my last escapade there.

Perhaps if I travel incognito, I can get past those Indiana troopers.

[H2O]

Evansville? That's south of the Mason-Dixon Line isn't it? I'm not sure if I am allowed to return to the 'South' after my last escapade there.

Perhaps if I travel incognito, I can get past those Indiana troopers.

 

Some of those ISP troopers might be offended by that Mason/Dixon quip, and I won't even ask why they would be watching out for you. lol

Shawnee forest in your state is one of our favorite weekend rides!

[H2O]

So far, so good!

Changed the oil. Changed the fouled plug. Installed new vacuum line between cylinder and vacuum advance. Tapped on the left front carb several times.

Started it up and it's like it was several years ago when I bought it.....................hardly any choke needed and it's idling smooth as silk again.

Let it run for two minutes while I tapped on the carb again. Throttled it up to around 2K a couple of times and let it idle. Turned it off. Pulled hose of dampener and turned key on.....no gas coming through vacuum hose anymore.

Put vacuum hose back together. Started it up and rode a few blocks then came back. Listened to the smooth idle for a minute then turned it off. Pulled vacuum hose off dampener again. No fuel showing.

Turned key on with vacuum hose still off and no fuel coming through.

Wahoo!

Bob Evans?

[BlueSky]

Congratulations!