Guest vfr2102 Posted January 24, 2008 Share Posted January 24, 2008 i have a 1987 vfr 750 it doesn't want to start, in mesiing with the fuel pump it started running i rode a little (20 min) that day and it hasn't started since, i know it's getting fuel. but when i tested voltage to the spark plug i dont get quite 2 volts. how many volts approx should i get? and i think either one of my coils is bad or possibly: the guy who owned it before me put a ungo alarm on it which is gone now but could have messed up a ground maybe. any advice is much appreciated thank ride on -jim Link to comment Share on other sites More sharing options...
turtlecreek Posted January 24, 2008 Share Posted January 24, 2008 how (where) are you measuriing the voltage to the spark plug? i am pretty sure the spark is at 40k or more volts! probably the best way to check your coil is to check input and output resistance (unplugged of course) as the coil is nothing but a transformer. sorry, i dont know what those resistance values should be, but if they aren't the same on both coils or if you have a short, you definitely have a problem. Link to comment Share on other sites More sharing options...
squirrelman Posted January 24, 2008 Share Posted January 24, 2008 If you have a bad coil you will have infinite resistance (no connection) between the 2 low voltage terminals. You can also check between the sparkplug wire and ground for some continuity. In practice, coils very seldom go bad, so your problem may be elsewhere..... Link to comment Share on other sites More sharing options...
Guest Posted January 24, 2008 Share Posted January 24, 2008 If you have a bad coil you will have infinite resistance (no connection) between the 2 low voltage terminals.You can also check between the sparkplug wire and ground for some continuity. In practice, coils very seldom go bad, so your problem may be elsewhere..... there's about 12 v going up to the coil, 1.22v constant to the plug when key is on but is not being started and 1.33 (a little bit more) when i hit the start button. so u think just trace wires and try to find a bad one? Link to comment Share on other sites More sharing options...
squirrelman Posted January 24, 2008 Share Posted January 24, 2008 that sounds about right.....check for sparks on all wires while cranking... the coils are all the same, so interchangeable, so testing is just switching them around....... Link to comment Share on other sites More sharing options...
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