Snaggletooth Posted July 18, 2012 Share #1 Posted July 18, 2012 Ok, been a lot of conversation lately about fuel pumps and now I'm chasing a problem with mine.... me thinks. First of all the bike is in good shape and most possible issues have been addressed in the past. Fuel tank lined with expoxy. Fuel filter and petcock shows clean and free. (Opened the tank to inspect) Fuel lines have all been replaced Tank vent clear and free of obstuctions. Carbs in good working condition and fuel bowl levels at spec. Good fuel flow through system. Air filter clean. Sync done recently. Electrical connections recently checked and found to be clean and sealed. Cooling system clean and working properly. Bike is not over heating. Charging system and electrical working properly and in good condition. Different fuel bought over a week from different stations. The problem only happens when the temps are in the top end of the 90's or over 100. Everything works fine in cooler temps and no problems of any kind. What happens is the bike, at highway speeds (60 - 75 mph) after being ridden for a distance in hot temps just stalls and sputters out. It will cranks right away but needs to sit for a bit before starting again. The first time it happened I wrote it off as a possible vapor lock. The bike had been sitting out in the sun since early morning and I didn't leave work until 2:00 PM when it was 101 degrees out. I only had a gallon and a half in the tank so I figured with the heat maybe I was vaporing. After 15 minutes the bike fired up and I rode home with no furture problems. I did check the vent line at that point. I filled the tank the next morning and ran about 100 miles that day in 80 degree temps and no problems. The next day it did the same thing again with a over half a tank in temps close to 100 again. Same thing. Let it cool down for bit and ran on home. It's done the same things twice more since then in the high temps but I made note that the digital voltmeter was showing a nasty fast drop from the usual 14.2 volts to 13.5 -13.8 right as the bike started to sputter. Not normal. And again today on the Interstate when it was 97 degrees. So knowing everthing I've checked is working as it should, almost, with the sudden drop on the voltmeter just as the bike stalls out I'm starting to question the fuel pump itself. NOTE: I can't say I've seen the volt meter dropping prior to the stalling, only note it as the bike is stalling. Is it possible the pump itself is stalling out do to a heat related failure causing the drop in the volts? It functions properly when cooled off. I can not get the bike to stall while on the stand and letting it run hot. It only stalls hot and under load. Kind of got me scratching my head... Mike Link to comment Share on other sites More sharing options...
OB-1 Posted July 18, 2012 Share #2 Posted July 18, 2012 I think the problem is the fuel pump. The stock pumps can be intermittent when they begin to fail. Just my guess and worth everything you paid for it. Link to comment Share on other sites More sharing options...
Dano Posted July 18, 2012 Share #3 Posted July 18, 2012 Have you checked the tank venting line? Hooks up at the filling hole, then runs down. Has a shut-off in it if'n you roll over, along the right side rear sloping frame visible with the side cover off. Just an idea..... Link to comment Share on other sites More sharing options...
dacheedah Posted July 19, 2012 Share #4 Posted July 19, 2012 I would drain the fuel from the tank and pull the petcock. look at the screens, and see id they aren't clogged with junk or that the screen is serviceable. Good opportunity to get a look at the inside of your tank also to assess the condition. I would look at the hose from your filter, if I remember right that does a 180, make sure it's not kinked before the pump. If that's all good I would start with fresh clean gas and give it a shot Link to comment Share on other sites More sharing options...
Snaggletooth Posted July 19, 2012 Author Share #5 Posted July 19, 2012 Have you checked the tank venting line? Hooks up at the filling hole, then runs down. Has a shut-off in it if'n you roll over, along the right side rear sloping frame visible with the side cover off. Just an idea..... Uh yeah, couple times. And no vacumn at the filler cap either (which would be caused by a plugged vent line) It's got every sign of actual vapor lock but I can't explain the sudden drop on the voltmeter. Still chasing for a shorted wire but that should be a lil more extreme on the voltmeter. Link to comment Share on other sites More sharing options...
dingy Posted July 19, 2012 Share #6 Posted July 19, 2012 Uh yeah, couple times. And no vacumn at the filler cap either (which would be caused by a plugged vent line) It's got every sign of actual vapor lock but I can't explain the sudden drop on the voltmeter. Still chasing for a shorted wire but that should be a lil more extreme on the voltmeter. The drop in the volt meter might indicate the pump is sticking in the energized position and not releasing to pull back, thus keeping current flowing through coil in pump and dragging voltage down with it. Gary Link to comment Share on other sites More sharing options...
Snaggletooth Posted July 19, 2012 Author Share #7 Posted July 19, 2012 So more than likely simple pump failure and the heat is not related, or maybe just a contributing factor at the least? Link to comment Share on other sites More sharing options...
dingy Posted July 19, 2012 Share #8 Posted July 19, 2012 So more than likely simple pump failure and the heat is not related, or maybe just a contributing factor at the least? Still could be heat related, but not in so far as vapor lock. The high heat could be aggravating a lingering pump issue. I looked for turn signals for you, but didn't find any. I have a parts bike I bought arriving tomorrow, I will see whats on it. Gary Link to comment Share on other sites More sharing options...
KIC Posted July 19, 2012 Share #9 Posted July 19, 2012 I believe one of my 84 parts bikes stll has the fuel pump on it and one of them has the rear turn signals if you need them . Link to comment Share on other sites More sharing options...
pmelah Posted July 19, 2012 Share #10 Posted July 19, 2012 heat will be a contributing factor hot gas heat of day hot roads and a weakining pump as the pump gets hotter with no way to cool off it will show a drop on the meter a friend just went thru this he changed the filter 3 times and the pump once the pump was the problem it had the same symptoms you described with yours snaggletooth i also went thru it in the suburban 2hrs. from the house not fun Link to comment Share on other sites More sharing options...
Snaggletooth Posted July 19, 2012 Author Share #11 Posted July 19, 2012 Hey again, Checking on the Mr. Gasket 42S fuel pump. Got one down the street from me so I might just swap that out. I have a spare OEM pump but not sure if it's worth installing. I did find a set of turn signals yesterday on fleaBay for $19.00 with shipping so I grabbed them. I guess that rubber knuckle joint don't last forever. But thanks, Mike Link to comment Share on other sites More sharing options...
reddevilmedic Posted July 19, 2012 Share #12 Posted July 19, 2012 Hey again, Checking on the Mr. Gasket 42S fuel pump. Got one down the street from me so I might just swap that out. I have a spare OEM pump but not sure if it's worth installing. I did find a set of turn signals yesterday on fleaBay for $19.00 with shipping so I grabbed them. I guess that rubber knuckle joint don't last forever. But thanks, Mike sent a PM. ya, i did the 42s with no issues now for about a year. good luck! Link to comment Share on other sites More sharing options...
Snaggletooth Posted July 19, 2012 Author Share #13 Posted July 19, 2012 Thanks Mike Link to comment Share on other sites More sharing options...
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