smackdoogle Posted September 6, 2012 Share Posted September 6, 2012 I've been commuting to work on my '93 VFR last week and this week and traffic has been fine and the bike has been running great. Getting between 42-48mpg. Great ride. Yesterday morning and this morning traffic going on base was backed up so I would end up waiting in line for a few minutes. Once the temp. gauge gets to the halfway point and the fan kicks on the idle gets really rough and eventually drops too low and it dies. She fires right back up though and the rough idle process starts all over. Once I get the bike moving and the fan shuts off she idles fine at stop lights until the temp rises and then the process starts over. At first I thought the carbs needed sinking but I ruled that out since she starts up fine when cold and idles fine when warming up. I'm thinking it has something to do with the fan since it starts when the bike gets warm enough for the fan to kick on. I don't know why that would happen though since the fan doesn't pull that much juice does it? Suggestions? Ideas? Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 7, 2012 Member Contributer Share Posted September 7, 2012 i think you have an air leak some place.. when cold the rubber shrinks and seals what ever hole or cut.. then when warmed up it leaks.. in any case.. PM sent.. Link to comment Share on other sites More sharing options...
Member Contributer kaldek Posted September 7, 2012 Member Contributer Share Posted September 7, 2012 Check your voltages when hot (strap a multimeter to the bike). If your volts are really low it may not be enough to drive the spark plug coils, hence the stalling. If you have a weak/faulty stator they tend to also drop their power output when the bike is hot as well, which makes the problem worse when the fan kicks in. If your fan is dodgy it can pull heaps of current which can drag the voltages down really low. A really quick/immediate test while riding is to turn off your headlights (if your bike has a headlight switch) because they pull 100 watts as well. Turning them off will let you know if it's a charging system problem because the bike will likely not stall then - i.e. the charging output should be enough to run the fan still. You'd expect that your battery would carry the load for you even with the charging system being stuffed but my experience is that's not always the case. Link to comment Share on other sites More sharing options...
smackdoogle Posted September 7, 2012 Author Share Posted September 7, 2012 Thanks for the suggestions. I'll be checking it out this weekend. Hopefully its an air leak (easier) as opposed to an electrical gremlin to hunt. Link to comment Share on other sites More sharing options...
smackdoogle Posted September 8, 2012 Author Share Posted September 8, 2012 Voltage of battery with bike off after 1000 miles of riding in 7 days is 12.7 I think I'm doing alright there so I'll check vacuum lines and the fan. Link to comment Share on other sites More sharing options...
smackdoogle Posted September 8, 2012 Author Share Posted September 8, 2012 ******UPDATE****** So, I tore the bodywork off and checked the air lines. I decided not to de-pair since I didn't have any caps or any way to make block off plates. I checked the lines and a few were loose or could have been letting air in. Put the tank back on and let it idle till hot. Once the temp gauge got to the half way point the same issue came up. Rough idle and it was starting to die. I noticed the fuel filter (clear FRAM) was nearly empty and a lil foggy. I then remembered on my VF1000R that I was using that same type filter on, once the engine got up to temp the fuel wouldn't flow through the filter. I pulled the fuel filter off, re-routed the fuel line and let it warm up to temp again. The fan cycled 4 times and the idle never got rough. I'm pretty sure the problem is fixed. The culprit, fuel filter......again. I'll now for sure when i sit in traffic at the navy base gate on Monday. Thanks for the suggestions though everyone. Link to comment Share on other sites More sharing options...
Member Contributer kaldek Posted September 8, 2012 Member Contributer Share Posted September 8, 2012 Huh, I thought based on what you said that it was "exactly" when the fan came on. So it was just more like "around the same time" then? Link to comment Share on other sites More sharing options...
smackdoogle Posted September 9, 2012 Author Share Posted September 9, 2012 Huh, I thought based on what you said that it was "exactly" when the fan came on. So it was just more like "around the same time" then? Yeah, I guess I wasn't clear. It seemed like "around the time" the fan came on. Sorry about that. Link to comment Share on other sites More sharing options...
GearWhyne Posted September 15, 2012 Share Posted September 15, 2012 Does the fuel pump come on at idle? Maybe you needed a new filter. Link to comment Share on other sites More sharing options...
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