Hello,

I recently purchased a 110CC ATA110F style ATV that has been hard starting. After doing some digging I found 2 problems. First, I'm not seeing charge voltage with the engine running or revving. I have a 4 wire regulator on the machine but I'm not finding a good electrical test procedure for this unit. White, Yellow, Red and Green are the 4 wire colors. What should I be looking for regarding voltage and/or ground? Secondly, the engine will crank at what I think is an acceptable speed but I've noticed that I have weak or intermittent spark while cranking. If I hook a batter charger up to the battery and repeat I get good consistent spark and the engine starts easily. Once that engine is running it stays running and the kids have ridden for hours at a time. I have chased the positive and negative battery cables and ensured that I have a good path to ground from the battery but not sure where else to look from here. Tips, tricks, advise or links all appreciated.

 

With a voltmeter across the battery, the voltage should slowly rise, not always matched to engine revs and, with those little bikes it can be a very slow rise. However if you switch the engine off, you should see a sharpish drop in voltage, may not be a big drop 0.5 volts or so, but noticeable. With AC CDI ignition the charging/battery circuit is totally separate from the ignition system so you shouldn't get much difference in the spark, other than the jump start may be faster. With DC CDI systems the spark is dependent on the battery so with it dropping to about 10v when starting, you are getting less power to the CDI, so a poor spark. Check compression too, as that gets lower bikes get harder to start, much under 90psi and either valves need setting or it is time for a top end rebuild.

 

Hello. The battery voltage doesn't change from idle to higher speed at all. I had the kids run the machine for quite some time this weekend and the battery voltage never went above 12.6V while running. So it seems it may be providing enough charge to keep the battery from going dead but it's not putting any charge into the battery. I'm wondering if there isn't some kind of wire harness issue that may be creating additional voltage during crank that the battery charger is making up for.

 

As I wrote above charging voltage isn't always directly related to engine revs. Some of those small engines don't have a proper regulator, just a rectifier, so the manufacturers deliberately make the alternator feeble, so that it doesn't overcharge. I would have expected better than 12.6v but, if you get a rapid drop back to 12v when you switch off, you know it is charging when running, if voltage doesn't drop at all, it isn't charging. Some two wires to alternator systems are single phase, some use earth as the third phase wire, so electronically they can be quite complex but, if they are not working, there is only the battery, rectifier, stator and the wiring, to go wrong. You can test for high resistances in the wires, and check a battery for being good under load. If wiring and battery are OK, it is easiest to just swap out the rectifier and, if that doesn't fix it, only the stator is left.