Ignition or fuel

Hey all. Posting under carb and ignition sections. I've searched extensively too.

I get a wavering tach needle sometimes just cruising around 4K RPM, at which time the motor is running smoothly. I just noticed this riding in this morning so it may point to an ignition issue.

I know there are a lot of diagnostics to run but thoughts, gut feel, etc.? Thanks!

If it's carbs, it sounds like main jets. Can't tell if your bike has stock pipes and airbox? Would also make sure timing advancer is releasing correctly.

Yup I checked timing and the advancer, and my bike is pretty much all stock.

It could be dirty carbs. When did the problem start? Was the bike running well on a regular basis and then one day the problem just popped up? Prior to the problem starting did the bike sit unused for more than a couple weeks? Ed

I've only owned the bike for a short time and only recently tried running it up to redline (it needed front suspension work, brakes rebuilt, mc replaced, etc so was hesitant to push it much!). Since I've owned it I've run it regularly.

I'll go through the ignition system next. It's running ok while the tach is fluctuating so maybe just the tach.

If you have a kickstand switch, that can sometims cause ignition stumbles from the switch vibrating.

The switch is designed to kill the ignition if the kickstand is down when the bike is in gear. When the switch, or kisckstand vibrates, the switch acts like it's down.

Interesting, I'll have to check that. I don't think my switch works but I'll check before I ride home!

Troyn wrote: I've only owned the bike for a short time and only recently tried running it up to redline (it needed front suspension work, brakes rebuilt, mc replaced, etc so was hesitant to push it much!). Since I've owned it I've run it regularly.

It's possible the previous owner let the bike sit for a while with fuel in the carbs - not a good thing to do. I would drop the bowls off the carb bottoms and see if everything looks squeaky clean up in the carbs and in the bowls (a mirror and small flashlight will help). You should be able to do this with the carbs still on the bike. If things inside the carbs don't look really clean I would pull the carbs and clean them. Ed

If you haven't cleaned the fuel system, that's #1. Take the tank off and rinse it out with clean solvent or gas. Clean the petcock assy, install or replace fuel filters. You can rinse the carbs out from the top: remove the drain screws and shoot carb cleaner down through the fuel lines. Replace screws and fill carbs with liquid cleaner like gumout and let sit for a couple of days, then rinse again. That will remove some of the built up varnish and make it run better. You can also add cleaner to the gas like Seafoam. If you still have problems, carbs have to be taken off and cleaned/rebuilt.