QuestionQUESTION: Starts and runs ok for about 20 miles then looses power and stalls. It feels almost as if it's running out of gas except that it has a full tank of fresh gas.
Thanks for your help.
ANSWER: Michael, if the bike will go 20 miles, generally what happens is that the charging system starts to malfunction when the engine warms up, due to defective rotors. You can do a full troubleshooting routine by downloading the test info at http://www.electrosport.com
The bike ignition is battery-powered, so when the voltage drops down around 10-11 volts, the ignition system components shut down. Get a volt-ohm meter for testing of the charging system output and the ohms value on the rotor tracks cold and hot.
There is a vacuum-operated petcock valve on these bikes, but if it was the problem you wouldn't get that far down the road. There is a fuel screen inside the fuel tank, which requires draining the tank and removing the petcock to draw the screen out from inside the fuel tank.
Bill Silver
---------- FOLLOW-UP ----------
QUESTION: Alternator, battery, gas all check out ok. The problem stopped for two weeks then returned for one day. It usually starts after a 20-30 mile run on the freeway(65-70 mph) when coming to a stop. If I keep the rpm above 3500 it will keep running. I have checked the alternator both cold and hot,12.5-13.2volt both ways. The battery always has 12.4-12.7 volts.
Mike
AnswerMike, does it just stall, then restart at a stop, after the freeway run? Does it re-start quickly or with difficulty?
Perhaps, the pulse generator gets hot and starts breaking down, once the cool breeze of the highway is lessened. The two spark units, mounted back by the battery should be checked. If you see black oozing down from the units, they may be weakening.
Take some spare spark plugs so you can connect a couple to the 2 outside cylinders and check them for spark. Have a look at the plugs, anyway, to see if they are fouling or look overheated from a lean condition, instead. If you are losing one coil, momentarily, it could be the coil overheating or the spark unit acting up.
If you know you have good spark when it is stalling, then you have to turn your attention to fuel supply issues, unless your valves are too tight. Run a valve adjust on it and check compression.
If you have the carbs off, disable the limit caps on the idle screws, so you can fine-tune the hot idle more effectively and help reduce the flat spot off of idle. If the accelerator pump is malfunctioning, then getting a good launch off of a stop sign will prove difficult.
A quick check on the charging system is to watch the headlight bulb intensity. If it brightens up when you rev the motor, then probably it is doing okay.
Make sure your vacuum hoses to the automatic fuel valve are good and tight. If that hose fails, you will get a vacuum leak and loss of fuel supply to the carbs.
Bill Silver
