Spark plug not grounded?

[carrier]

Hello All

Whenever I try to start my bike I turn it on, thumb the starter, and the engine will turn over but may or may not start. If it does I have to turn it off and back on and try again. Using a volt meter I checked the coils positive terminal and it gets a steady 10.5v and drips a bit when thumbing the starter. On the negative terminal it starts at 10.3v and drops a little more to 8.6v around. Doesn't that mean the coils are working? Sometimes during testing the bike would start and sometimes it wouldn't but the voltages were always the same. Could my spark plugs just not being grounding?

Thanks

[Fazerider]

The ground for the spark plug is the engine which is connected via a cable at the rear right hand side to the battery's negative terminal.
Your reading of 10.5 v sounds a bit low, the positive ends of the coils are connected via two switches and a fuse to the battery so you should be getting a couple of volts more than that assuming the battery is healthy. Exercising the run/stop switch with some contact cleaner might help.

[carrier]

I cleaned the engine kill switch last weekend, hoping it was that. It was not. I've also clean and sanded the contact between the engine and the wire that goes to the - bat terminal. Anything else?

[Fazerider]

If the battery is OK, you're losing a couple of volts somewhere between that and the coils. I'd focus on trying to find out where... the connector block for the ignition switch and the kill switch are in the box under the tank, corrosion or loose contacts may be to blame. Hopefully it's not the ignition switch itself, though you may be able to get some contact cleaner in there.

[carrier]

I'll check that tomorrow, thanks. Why would it sometimes work with only 10.5v and sometimes not?

[carrier]

The missing volts where from the battery not being 100‰ and the headlights being on. Battery topped up and I get 11.5v at the coils with headlights on. If I bypass the ignition switch I get 12v. Could it be not enough amperage?

[andybesy]

You should you don't just have a battery on it's way out? It's quite common this time of year.

Andy

[carrier]

had the problem even when battery was new