Hissing/pssss while running

[mzack]

'06 FLSTFI - a hissing/pssss sound when the bike is running. This stated a couple of hundred miles ago. Whatever it is, the bike doesn't seem to care and it runs as before. it may be effecting cold start-up - it has wheezed a couple of times in the last two weeks but fires easily on the second started try.

The sound seems to be coming from under the tank - and seems to be external to the tank but....

There is kind of loud hissing sound along with the fuel pump humming when the ignition is turned on that I had never noticed before. Both noises are together and all noise stop as soon as the pump is pressurized. A quick cycling of the ignition does not get the fuel pump to repressurize unless I wait 5+ seconds between cycling the ignition off/on.

The bike was originally sold in CA and has the charcoal evap cannister. All connections are good, all hoses apprear to be fine but I haven't lifted the tank as it has 4 gallons or so in there now. As I understand that system it is low pressure so probabaly wouldn't cause this kind of audible hiss.

I can hear this noise over the running motor - it is an intermittent hiss - it comes and goes in irregular intervals of few seconds or so.

I opened the tank up to see if I could spot a pin hole/perforation in the fuel hose but I have too much gas in there to see that now.

I sprayed STP Carb Cleaner around the intake plenum - where it bolts to the front and rear heads - and there doesn't seem to be a leak there. No sputtering or stalling when I spray the STP on it.

Do I have an upcoming issue with my fuel pump? What else draws vaccuum on these EFI systems - what am I missing? Ideas?

thanks guys -

Mike

[gunnut]

Sounds like a leaky hose inside the tank. Does the bike start right up or does it need to crank a bit before it fires?

[mzack]

...well I think the problem is solved. Would you believe that both of my compression releases were loose? The front cylinder more than the rear - it took 4-5 twists of the ratchet (1/3 turn per). I snugged them down and the noise is basically gone. I'll check them tomorrow when it's cold - something about tightening steel in aluminum.

Without looking at them - are they supposed to be installed with loctite (blue?) or do they get anti seize and a washer?

[niget2002]

The hissing noise you're hearing when first switching to run could be your IAC motor resetting (in conjunction with the fuel pump). Mine makes an audible noise sometimes.

I don't remember if I hear it when I turn the ignition on or when I switch to run.