weak spark on 750E common?

[drhermanstein]

I'm getting popping and banging on what appears to be a weak sparking 750E. Stator provides good voltage , new battery sits at 13.6 at rest. all plugs have a weak dull blue spark. wires and caps are all at 5.5k ohms.
NOS wire harness on the way. I hope that will work.

Fuel, carbs, and valves are all OK

[Billy Ricks]

Search for threads on adding a relay to get power to the coils directly from the battery instead of the stock harness.

[drhermanstein]

Search for threads on adding a relay to get power to the coils directly from the battery instead of the stock harness.

Great idea, I'll try that asap. I have a number of good waterproof relays that would work real slick.

[tas850g]

what does a relay do?

[doctorgonzo]

what does a relay do?

It's a "Must do" modification in my opinion. In the original wiring the hot wire for the coils passes through the kill switch and sometimes other switches on the bike. This causes (especially with 30 year old switches) resistance so the 12V that left your battery may be 11, 10, even 9 or lower volts by the time it hits the coil, translates to weak spark. You use a relay to wire a hot directly from the battery to the relay and from there to the coils so you get the full output of the battery for spark. The relay functions to cut that juice off and on when the kill switch is used, ignition is off, etc.... Search for "Coil Relay Mod" and you should find a nice pictorial on it. I am NOT an electrical guy and I did it in an hour.

[drhermanstein]

It's a "Must do" modification in my opinion. In the original wiring the hot wire for the coils passes through the kill switch and sometimes other switches on the bike. This causes (especially with 30 year old switches) resistance so the 12V that left your battery may be 11, 10, even 9 or lower volts by the time it hits the coil, translates to weak spark. You use a relay to wire a hot directly from the battery to the relay and from there to the coils so you get the full output of the battery for spark. The relay functions to cut that juice off and on when the kill switch is used, ignition is off, etc.... Search for "Coil Relay Mod" and you should find a nice pictorial on it. I am NOT an electrical guy and I did it in an hour.

Thanks for the suggestion. Did the mod. It started up even though plugs were likely fouled and wet!

[chef1366]

what does a relay do?

http://members.dslextreme.com/users/bikecliff/images/coil_relay_mod.html