klebocna101 Posted April 22 Share Posted April 22 Hi guys, recently I got vfr800x y2015 with 9600km on the clock and noticed one strange sound when I got back to garage. You can hear it from third second of attached video (volume up). Sound repeats every 1-2 minutes but when tank cap is open this does not happen. It all stopped when engine cooled down. Cleaned one-way valve in the tank cap. While blowing some air into the breather coupling, I could hear air is coming out of the hose under the engine but I really had to blow hard to get air out. Any ideas what to check? IMG_5463.MOV Quote Link to comment Share on other sites More sharing options...
Member Contributer Skids Posted April 22 Member Contributer Share Posted April 22 Totally normal so don't worry. Quote Link to comment Share on other sites More sharing options...
klebocna101 Posted April 22 Author Share Posted April 22 Thank you. May I ask what is the root cause of this sound? Quote Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted April 22 Member Contributer Share Posted April 22 9 hours ago, klebocna101 said: Thank you. May I ask what is the root cause of this sound? You may Sir........ Copied this info from the 8gen. posting "Vent System - Update" from 2021. Assume the VFR800X has the same filler cap and vent system. Beware the tank vent hose! Pressure Relief - The common noise we all have heard, and as one member puts it "sounds like the Fuel Pump is priming with power off" or just a few second buzz, fluttering or gurgling sound. This is coming from the Pressure Relief Valve in the filler cap as the tank pressure builds and overcomes the spring tension on its valve. This process will continue to repeat any time slight positive pressure builds in the tank. As you stop a warm engine the heat transfer to the tank causes this to happen more frequently and if you open the filler cap in between the venting you'll always get a very slight pressure relief. Vacuum Relief - Negative Pressure relief also has to overcome slight valve spring pressure as the fuel level drops while riding. On cold days when topping up your tank you may notice very slight suction as you open the tank cap. So depending on temperatures and riding conditions it is Normal to have either slight Vacuum OR slight Pressure as you open the cap. The emphases being SLIGHT. Blocked, Kinked or crushed Breather Hose = DANGER! The problem with the 8gen is the first 12 inches or so of small diameter breather hose. When the Fuel Tank is raised to the maintenance position, the hose is pulled up through a lot of piping and general clutter in this area. If this hose is not manually pulled outwards at the small to large hose coupling taking up the slack as the tank is lowered, you run the chance of a blocked kinked breather hose. The nasty effects of a blocked breather cannot be overstated on these bikes! - Strong Vacuum, can make it impossible to open your filler cap. The Fuel Pump has enough strength in increasing the vacuum while riding to physically damaging your tank, bending the sides inwards. - Whilst having the bike in the sun strong positive pressure can distort the underneath of the tank deforming it outwards. Or virtually blasting the filler cap open as you unlock it. Any signs of strong pressures, negative or positive when opening the filler cap is a warning to check the breather hose. 1 Quote Link to comment Share on other sites More sharing options...
Member Contributer bmart Posted April 23 Member Contributer Share Posted April 23 I bet that's a...relief. 🙂 Quote Link to comment Share on other sites More sharing options...
klebocna101 Posted April 23 Author Share Posted April 23 Thank you. I had same thoughts but was not sure. So joy of removing plastics here I come. Quote Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted April 23 Member Contributer Share Posted April 23 4 hours ago, bmart said: I bet that's a...relief. 🙂 Haha yep, vented relief I hope, horrible that blocked breather feelin, just gotta get that gas out! Quote Link to comment Share on other sites More sharing options...
klebocna101 Posted April 23 Author Share Posted April 23 🙂 🙂 🙂 Quote Link to comment Share on other sites More sharing options...
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