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Fuel tank breather check valve for carbie SS.

4K views 16 replies 6 participants last post by  Iwannaduc 
#1 ·
I'm looking for a replacement fuel tank breather check valve for a carbie 900ss. Mine is completely corroded. Does anyone know where I can get either the OEM replacement or aftermarket replacement that works? I have one from some other machinery, but this one is pretty chunky at almost an inch in diameter. I'd want something a bit smaller like the original. Appreciate your suggestions!
 
#3 · (Edited)
Depends on where you route the hose, (My 95 dives down the steering stem hole so it still is inline), but those $10 anodized ones for dirt bikes at CycleGear work fine. Just put a longer hose on and put the vent breather piece at the end instead of hanging out on top of the tank with two hoses. Miy 91 routed is under the fairing and zip tied to the frame out of sight unless I put the CR fairing on.
 
#5 ·
I have an additional, related question - so the one that I put on from the other machinery (it's from a pile of parts for things like industrial air compressors and water cooler and stuff like that) works well as a one-way check valve, but I found what could be an unintended consequence, maybe? The way I understand is that the breather valve should let the air in the tank to replace the fuel that is being sent to the carbs, right? What's happening is that now the one-way check valve works, every time I open the filler cap, it blows out puff of (petrol smelling) air, meaning that it appears to build a positive pressure inside the tank (from the heat?). Is this normal? The filler cap obviously is not vented, is there supposed to be the secondary vent? I'm still very new to 900SS, so I'm very curious to learn. By the way, I had an early GSX-R 750, which had a breather hose, which had no check valve, and I don't remember that it leaked fuel.
 
#6 ·
The cap usually does have a vent into the chamber under the cap. from there you have one or two ways for it to exit.
#1 the cap drain that should be the recessed hole at about the 7-o'clock position if you are setting on the bike.
#2 later cap flanges with California emissions there will be a rubber bumper looking thing at six o'clock. this is actually a passageway from the cap to the charcoal canister. if either of these holes/vents are plugged they cannot de-pressurize the tank. It is not un common to have a tank vent plug either internally from rust or externally from insects or simply pinched off.
 
#7 ·
The cap usually does have a vent into the chamber under the cap. from there you have one or two ways for it to exit.
#1 the cap drain that should be the recessed hole at about the 7-o'clock position if you are setting on the bike.
#2 later cap flanges with California emissions there will be a rubber bumper looking thing at six o'clock. this is actually a passageway from the cap to the charcoal canister. if either of these holes/vents are plugged they cannot de-pressurize the tank. It is not un common to have a tank vent plug either internally from rust or externally from insects or simply pinched off.
The overflow, or the cap drain is working fine. There's the recessed hole there (the 7 o'clock hole that you are talking about, I think), it's actually not a hole. I looked at it when it was off the fuel tank, but there's no hole that goes through. Is that supposed to be open? I guess I can drill it out.

 
#12 ·
An interesting info about the CA emission stuff. Because the fuel filler cap mechanism was seized, I had to disassemble the cap, and noticed that there was an elaborate passage for something, but now I see that it’s for the vented gas. Anyway, so the drain is working fine, meaning the positive pressure buildup is not venting passed the sealing part of the cap. I poked the little hole on the cap’s latch cover, and it’s not blocked. I may have to take it apart again to study the filler cap one more time to see how it works, it might be more complicated than I thought.
 
#14 · (Edited)
I took the filler cap apart. The small hole at the bottom of the latch, there’s a lot of space inside there that houses the latch, and the bottom of the lock. There’s a plate, then there’s the spring loaded filler cap seal. There’s a little rectangular chamber that has two small holes that leads into the chamber that’s shaped like two circles in shape of ‘8’, from which there’s a pathway defined by the cap and gasket to the little hole that lines up with CA emission related hole that ducvet mentioned. Here’s the weird thing - mine had a rubber piece in the shape of ‘8’ that fits in that chamber that blocks the flow of the vented air. I removed the rubber piece, so that vented pressure can leave through the cap area. I’ll take a ride tomorrow to see if that’s what, but I’m pretty sure that’s what the problem has been. I should have taken some pictures.
 
#16 ·
Erm, yeah? See, the one-way check valve was shot, so I got new one, right? It does let air in to the tank, not out, right?, so to replace the fuel spent with air, basically. But since I replace the check valve, I noticed that the tank holds positive pressure inside, probably from heat, since while it lets air in, it’s not letting air out. The logic suggests that there’s no other place to let the pressure out, so I think it’s a reasonable conclusion, at least it seems to me.
 
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