1990 Suzuki King Quad 300cc Kicks and bucks when accelerating unless ignition switch is in LIGHT position.

[Tuzz]

Bucking started about a month ago and works ok after 1/2 hour warmup.  Today while working on it i discovered that if i put the ignition switch in LIGHT position it runs fine right from the start.

I'm stumped!  Any idea why this could be?  

[Mech]

Check the charge regulation at the battery. Before starting the battery should be about 12.5 volts, a couple of minutes after start up it should be 13.5 and after a while it should top out at about 14.5 volts. If it's not charging, or charging to high, you need to check the wiring to and from the regulator, earths and power. If the power to and from the battery, and the earth is good, then the regulator is probably playing up.

I say probably because they don't normally come right after a half hour of running.. It could be getting warm and then functioning properly, or some bad connection or a dud battery could be causing it.

[Tuzz]

It works fine when the lights are turned on.  Does that make sense for a bad regulator?  Also it specifically is a: 1998 SUZUKI LT-F4WDX

 

[Mech]

Yeah the headlight helps if the regulator isn't working, but the regulator can be not working because the battery is dud, or because an earth to the regulator isn't good, or because the wire taking the power from the regulator to the battery is crook. It may not be a faulty regulator.

I'm in New Zealand and we have different charging systems to the American models, but our regulators seem absolutely bullet-proof. I've seen it claimed over there that all suzuki regulators are absolute rubbish and should be ditched for an after market as soon as you get the bike. But that's only one guy says that, and he always tells people not to check the earths or power wire, that it is always only the regulator.I think that's a stupid attitude and bad advice.

Check the charging as I suggested and it will show up any of the faults I suggest it could be. If the power wire from the regulator is broken or got a bad connection the voltage won't rise. If the earth wire's broken or got a bad connection it won't regulate. If it charges, and regulates, the system's fine.. but it won't be probably because of your symptoms. I've seen it heaps of times..

[kiriyaaoi]

I've seen this in a few videos, if the regulator has failed and is outputting crazy high voltages, like 18v- it will cause the ignition system to not work properly. Running with the lights on puts just enough of a load on it to pull the voltage down to a level that the CDI doesn't freak out.

[Gwbarm]

👍

[Chucksta]

About the voltage regulator effin' up the running.... It's true. 

Got a '97 king quad.. a freebie fixer upper..  Got it to start, and run, etc.etc. But, once the battery was fully charged, it'd run O.K. at idle, then buck and jerk and run like a bag of hammers. I couldn't find the problem to save my life. I had the meter out to try and get the power port 12 volt thingy working, and the meter showed 18.2 volts..  

Google quickly let me know that this was WAY to high and would have " adverse effects" on ignition, headlights, etc. I changed the voltage regulator, and it's been all good ever since. On;y crappy part was having to take off the plastics to get at it. At the end of the day, I couldn't get the old one out ( rusted mounting screws), so I just stuffed it in there, and zip tied it into place. 

When you put it back together, be sure not to disturb the trigger wire to the starter relay. 

Don't ask me how I know this..

[Gwbarm]

Good info here, thanks for sharing.