Lights on - Revs drop

[GavD]

Been getting the '98 steamer back on the road after 3 years laid up. Had a few problems with the carbs gummed up, but now she's ok in that dept. When it's idling and I switched the headlights on the revs really drop - by something like 800 revs. Gotta get her idling at about 1900 with the lights off to get her to keep running with the lights on. Batt is new and well charged.

Any ideas anyone?

[rybes]

my guess would be your alternator or chargin circuit. summink will be playin up somewhere. look for broken wires and corroded connections before thinkin its the alternator. to check if the alternators workin. leave the bike overnight then in the mornin check the voltage. remember it. start the bike up and when itll idle on its own with no choke, take another readin. if the alternators woekin it should read around the 14 volt area. hope this helps :D

[GavD]

Already checked that, 13.4v with the engine off, 14.5v with the engine running and lights off (1900 revs), 14.4v with engine running and lights on (1100revs).

Strange!!

[oxnsox]

Sounds, and looks, like the alternator is working.
I'd summarize it a couple of ways (from an electrical perspective):
- Either the regulator is cutting in too early, and the load is too much for the fuel settings.  OR
- The Carb settings don't allow for a bit of load at idle.

Not too helpful but then I'm a Girly owner

[iansoady]

Not a steamer rider myself but.....

This does sound quite normal. The lights put an extra load on the alternator. The power to supply this has to come from somewhere (ie the engine). So it's a bit like letting the clutch out a bit with the engine in gear.

Our sophisticated efi bikes monitor the engine speed at idle and if it drops open the IACV to let more air in hence maintain the idle speed.

If you have an efi car with aircon you can often see the revs drop slightly then recover when the compressor kicks in.

[GavD]

Nice one Oxnsox
It turned out that I hadn't cleaned the carbs as well as I thought. After another removal & blast with carb cleaner and compressed air, she's idling smoother and the revs only drop a couple of hundred now.

New chain and sprockets, oil and filter change and she'll be back on the road.