cabreco Posted March 4, 2015 #1 Posted March 4, 2015 Ok I have a mystery on my hands & need ideas. I have 2 bikes (My Venture & a CB750 ) I filled both tanks over a month ago. Today I took a ride on my Venture & noticed the gas gauge is down to 2 bars above empty with only 49 miles on the trip odometer (The CB750 is still full with 30 miles on its odometer) My bikes are parked in my garage, I am NOT leaking gas at all, SO where did my gas GO??? I have new lines, new clamps, no weeping. Is it plausible that it has been evaporating via the gas cap not sealing right anymore?
Peder_y2k Posted March 4, 2015 #2 Posted March 4, 2015 That much won't evaporate that fast. Check the motor oil level as there could be an internal carb leak draining into a cylinder. Then again, maybe the tank float is caput leading to a false reading. Pete, in Tacoma WA USA
Flyinfool Posted March 5, 2015 #3 Posted March 5, 2015 Mine did that once. Half of the tank disappeared while locked in the shed. No drip marks on the floor, none in the oil, no clue where it went. It fixed its self and the missing gas never happened again.
cabreco Posted March 5, 2015 Author #4 Posted March 5, 2015 Yeah it's weird, The float is accurate. Normally when the bike is in use I get about 200 mile on a tank consistently. It's been sitting awhile because of the snow, which it usually is always in use. May b a leak into the carbs but then wouldn't she be hard to start being flooded? Maybe a better petcock (1st gen's suck) may be in order to shut the fuel when not in use
Peder_y2k Posted March 5, 2015 #5 Posted March 5, 2015 One carb leaking internaly won't make for flooded hard start. Pete, in Tacoma WA USA
friesman Posted March 5, 2015 #6 Posted March 5, 2015 hmmm....got a teenager in the house? have you checked your siphon hose lately? Brian
Venturous Randy Posted March 5, 2015 #7 Posted March 5, 2015 Andy, your bike will not leak much thru the carbs while just setting because of the tank being so low. I had a problem similar to what you are having where the fuel level would drop a few bars and it ended up being my sending unit in the tank was messed up. I pulled it out and could see the problem. Put another one in and it fixed it. Randy
BlueSky Posted March 5, 2015 #8 Posted March 5, 2015 If you are my age, maybe you had a senior moment and just thought you filled it up:backinmyday:
tz89 Posted March 5, 2015 #9 Posted March 5, 2015 Parked on the side or center stand? Just asking. With a gallon gone before you parked it, so the top overflow empty, I don't expect it flowed through the engine from tank, pump and float chamber. I would suspect the tank float, cold weather and maybe a little accumulated moisture combining to cause the mystery.
cabreco Posted March 5, 2015 Author #10 Posted March 5, 2015 Parked on the center stand. Well if it IS the float then if I fill it I should still have about 4 gallons in the tank right? Oh yeah I do have a teenager but he has my credit card for gas. I did consider a "senior moment" but I checked my credit card statement & saw that I filled both bikes on the same day. Damn curious thing.
flyday58 Posted March 5, 2015 #11 Posted March 5, 2015 Parked on the center stand. Well if it IS the float then if I fill it I should still have about 4 gallons in the tank right? Oh yeah I do have a teenager but he has my credit card for gas. I did consider a "senior moment" but I checked my credit card statement & saw that I filled both bikes on the same day. Damn curious thing. So how much did it take when you refilled? No odor of gas? My supply hose to the fuel filter was seeping. Took forever to find due ti the location under the tank.
cabreco Posted March 5, 2015 Author #12 Posted March 5, 2015 So how much did it take when you refilled? No odor of gas? My supply hose to the fuel filter was seeping. Took forever to find due ti the location under the tank. I haven't filled it yet (after a 73 degree day today it will be snowing tomorrow, go figure) So not sure yet. I replaced all my fuel lines last summer & replaced the filter & clamps as well.
bongobobny Posted March 5, 2015 #13 Posted March 5, 2015 OK just grasping at straws here but did you add any stabilizer to the gas? Modern gas does not store well so maybe the stale gas resulted in really bad MPG...
cabreco Posted March 5, 2015 Author #14 Posted March 5, 2015 OK just grasping at straws here but did you add any stabilizer to the gas? Modern gas does not store well so maybe the stale gas resulted in really bad MPG... Bob she wasn't down that long only about a month. (not by choice but by snow) I ride all year round. I would guess that a possibility but my CB750 is still filled.
Neil86 Posted March 5, 2015 #15 Posted March 5, 2015 The higher the resistance in the sender circuit the lower the reading....so you might have poor connection between CMU and sender.
Flyinfool Posted March 5, 2015 #16 Posted March 5, 2015 Start by filling the tank, if it only takes about a gallon then you know it is a problem with the sender / fuel gage circuit. If it takes about 3 gallons, then the gas is actually gone and you have an issue with the fuel system.
baylensman Posted March 6, 2015 #17 Posted March 6, 2015 Do a quick visual self check. Remove cap and peer inside, can you see the fuel. Rock the bike listen for splashing.
dna9656 Posted March 6, 2015 #18 Posted March 6, 2015 It probably migrated to the chain saw.... Mine did that once. Half of the tank disappeared while locked in the shed. No drip marks on the floor, none in the oil, no clue where it went. It fixed its self and the missing gas never happened again.
cabreco Posted March 11, 2015 Author #19 Posted March 11, 2015 So how much did it take when you refilled? No odor of gas? My supply hose to the fuel filter was seeping. Took forever to find due ti the location under the tank. Ok so I filled it up today. The gauge was at 1 bar but would occasionally bump up to 2 bars The fill up was 3.2 Gallons & I could see the fuel just below the neck after letting it settle through the baffles when I capped it
Semi-retired Posted March 11, 2015 #20 Posted March 11, 2015 OK just grasping at straws here but did you add any stabilizer to the gas? Modern gas does not store well so maybe the stale gas resulted in really bad MPG... On the same subject of "HORRIBLE GAS MILEAGE".....I had a one spark plug go south on me and, you'd think that with "one quarter" of your engine not providing power....you'd notice it in "performance" almost immediately. But for some strange reason......maybe because the engine puts out SO MUCH power when it IS running on all four.....I didn't really notice the performance thing, UNTIL I noticed the gas consumption phenomenon. Then and ONLY then, I tried hammering on the throttle......and it was missing and farting and stuttering all over the place. So.........after all THAT.............changed your plugs in the last 3 or 4 years???
cabreco Posted March 11, 2015 Author #21 Posted March 11, 2015 So.........after all THAT.............changed your plugs in the last 3 or 4 years??? New plugs replaced at the beginning of last season. Gas mileage she does fine. I get around 43mpg hywy & about 34 city. This gas just DISAPPEARED while sitting in my garage a month
Semi-retired Posted March 12, 2015 #22 Posted March 12, 2015 New plugs replaced at the beginning of last season. Gas mileage she does fine. I get around 43mpg hywy & about 34 city. This gas just DISAPPEARED while sitting in my garage a month OK, then.......the only other contribution I can offer is that this same phenomenon happened to my 1982 Suzuki GS1100G, shafty, and the "mystery" in THAT case turned out to be that the fuel tap had been left on........as it OFTEN is with bikes these days.......and I'd had a carb float "issue" (either with a stuck needle or a cracked float....resulting in its "sinking").....so that a huge quantity of gasoline drained from the tank, through the carburetor float-bowl....down the intake manifold......and eventually right down into the crankcase. So, this is a very REAL possibility......and if it's what happened to YOU.....be VERY cautious about starting/running your engine at all before checking the "integrity" of your engine oil. Start by checking engine oil level (via inspection window, dipstick, whatever.......then pull the drain plug remove a good "sample amount", 1/2 a pint or so, and look at and smell the oil to see if it hasn't been "polluted" by a possible internal fuel leak. Good luck......and let us know the outcome!
cabreco Posted March 12, 2015 Author #23 Posted March 12, 2015 OK, then.......the only other contribution I can offer is that this same phenomenon happened to my 1982 Suzuki GS1100G, shafty, and the "mystery" in THAT case turned out to be that the fuel tap had been left on........ Since the Gen 1 are not gravity fed (electric fuel pump) & the carburetor is a good 18 inches ABOVE the fuel pump, even with the petcock open (which it always is) I surmise the fuel would not be able to travel UP to the carbs. Now if it would have been my 81 CB750, I would say it would be a good possibility. As far being cautious before starting her, I'm afrad that ship has sailed as she has been out every day this week!
Semi-retired Posted March 12, 2015 #24 Posted March 12, 2015 As far being cautious before starting her, I'm afrad that ship has sailed as she has been out every day this week! Well.....those are all good things, Andy! But as far a solution to your "mystery" goes.......you and your bike are certainly making it difficult for us aspiring "Inspectors Clouseau"! Had (m)any other "submissions" of interest? Can't recall if some or all of the "obvious" questions have been asked: 1. Was the bike under lock and key? 2. Is the gas cap under lock and key? 3. Is any OTHER vehicle on the property "down a quart?" 4. Has this ever happened before....to ANY machinery on your property? 5. How's the gas mileage TODAY? 6. Have you set up security cameras since the incident? Wow. Tough one!
cabreco Posted March 12, 2015 Author #25 Posted March 12, 2015 Well.....those are all good things, Andy! But as far a solution to your "mystery" goes.......you and your bike are certainly making it difficult for us aspiring "Inspectors Clouseau"! Had (m)any other "submissions" of interest? Can't recall if some or all of the "obvious" questions have been asked: 1. Was the bike under lock and key? 2. Is the gas cap under lock and key? 3. Is any OTHER vehicle on the property "down a quart?" 4. Has this ever happened before....to ANY machinery on your property? 5. How's the gas mileage TODAY? 6. Have you set up security cameras since the incident? Wow. Tough one! Bike sat locked in my garage, locked & capped, I filled the CB750 on that same day a month ago, no issues, It's not my kid as he has my credit card for gas & uses my wife's car. All my vehicles have locking caps, I have a home security system & my bike has an alarm system. I filled it yesterday (still full) and there is no significant smell of gasoline in the garage. Yeah, that made everything even MORE confusing
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