86 FJ1200 Sputtering/Tach Jumping

[Prototype4342]

Hello all, so recently my FJ has developed an issue, it seems to start when the bike is warm but that may just be because I don't push it much when it's cold. When I have the throttle at certain positions it sputters like it's missing and the tach bounces upward [toward redline], I have also noticed when riding at night that the headlight flickers when it does this. Typically I notice it first when I try to get on it in 4th or 5th gear, then it starts happening in all gears when I hold it at that throttle position. Any ideas? It seems electrical to me but I'm not too sure.

[Mark Olson]

Start with the simple stuff, remove ground from coils and clean it with sandpaper/wire brush . Check you engine ground as well . Is your battery charging . Are the spark plugs ok. Are the coils cracked .

There is a bunch of other stuff butt start with this .

[Arnie]

It actually sounds like an intermittent short to me.
These can be very frustrating to find sometimes.
After you've done the normal stuff like Mark suggests, you might want to try running the bike in a dark garage (with the door open) at varying rpms and look for sparks.  Check everywhere the loom is close to the frame, and especially any "extra" V+ wires that you or previous owner may have installed.

[Flynt]

Start with the simple stuff, remove ground from coils and clean it with sandpaper/wire brush

+1...   This solved the same issue for me...  coil grounds were causing funny symptoms, but the tach symptom you describe was right on.

Frank

[Prototype4342]

Thanks guys I'll pull the tank off and see if the coil grounds are good. Could probably use some new spark plugs too.

[Prototype4342]

Where is the engine ground located?

[Mark Olson]

Your engine ground is located near back low on engine ,,follow neg batt cable and you will find it.