Guest Kue Posted May 7, 2012 Share Posted May 7, 2012 I have a great old VF750, 1985, that ran mostly great until about 6 weeks ago. The first really hot day, I was driving back and forth from Chapel Hill to Durham, and it started running really crappily. It wouldn't idle, had NO power, and I was cranking pretty hard to keep from stalling. Almost made it the last mile home (which was downhill) but stalled on the last hill. I waited a couple minutes but didn't really know what to check, since it had plenty of gasoline. Tried starting again after it had sat maybe three minutes, it started right up and felt normal; got me home fine. I thought it was a one-time thing, but a few days later, on another hot day, it failed again after about an hour of riding. Now as soon as it gets hot, it runs poorly and then stalls and I have to wait 10-15 min and it will start again. When running, it has plenty of power, and even idles well. Then suddenly looses power and then begins to stall and won't start again for 15 min. Battery seems to be charging fine, rectifier puts out the right voltage (14.8 volts). We have replaced a weak coil, the pulse generators, and the spark units, with no improvement. The only other thing I can think of that may be related is that I replaced the fuel filter and parts of its fuel line in January when the old rubber split and spilt the contents of my gas tank all over my work parking lot. Anyone have any ideas or suggestions? This is my first bike and I'm learning, but I just don't know where to go from here! Thanks! Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted May 7, 2012 Member Contributer Share Posted May 7, 2012 you keep missing a BIG clue.. ITS OVER HEATING!!!! is your coolant low? fill it up. is the rad fan coming on? if not check the fans thermo switch.. if it does.. then it 99% sure shot that your thermostat is stuck shut. replace it. .. Link to comment Share on other sites More sharing options...
Guest Posted May 7, 2012 Share Posted May 7, 2012 Good point, thanks for your reply. I'm at work but I'll definitely check out the rad(iator?) fan and thermostat. Coolant levels are fine, we've checked and rechecked. It does seem unlikely that it is overheating though, just since the temperature gauge seems to work fine and it has been failing when the gauge still reads low. In fact, failing seems to be pretty independent of internal temperature, since it has failed during long rides (temperature higher but still pretty normal) and more recently after only 5 minutes (temperature only barely registering on the sensor). Could this still be consistent with a bad thermostat / rad fan? I'll definitely check out what you suggested, but any other ideas, meanwhile? Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted May 7, 2012 Member Contributer Share Posted May 7, 2012 its possible... the fuel pump is cutting out at odd times.. a simple way to check.. unplug the wires.. unplug pump from gas lines. place a fuel filter where the pump was.. go for a ride around the area close to home. the down side of this.. if you ride flat out top speed ... the bike will "run out of gas" in about 7 to 10 min.. till you slow down to a 100 or so... Link to comment Share on other sites More sharing options...
Guest Posted May 8, 2012 Share Posted May 8, 2012 Next time you take it out, carry a small screwdriver and a rag with you. If it stalls out, turn the ignition off and loosen a couple of the drain screws on the bottoms of the carb float bowls-have the rag ready to catch fuel when (if) it runs out. If no gas runs out, you know you've got a fuel starvation issue. Another thing to check when it cuts off - open the gas cap and see if the bike will start. If it fires right up you could have a vent issue with the tank, not allowing the pump to pull fuel. Just a couple of thoughts - easy to check when you're on the side of the road... Link to comment Share on other sites More sharing options...
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