KA100 Starter issues

Hi Guys - ran all day Sunday no issues. Then on the grid for the feature and the electric start doesn’t go. We got it to fire with an external starter and had a great race. But I am not sure where to start to diagnose the starter issues. I have heard the switch can be problematic, but also brushes go too. All connections seem good.

I am ok with a multimeter, but not the best. Any tips would be appreciated.

Unplug the kill switch and try again. East place to start and known failure point.

Thanks Andy- but I already have that disconnected as I don’t use the cut off. I started with my battery- it is not a dead battery

My engine builder told me check brushes next as long as no wires were exposed from battery harness to the engine.

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If it sounds like a whine without kicking into the gear it may be your Bendix. I hear they go fairly often if they are not cleaned/maintained.

KA 100 Starter issues
1.“Flat Battery” - battery may have charge but not enough to kick the engine.
2. Chain lube/dirt ingress into Bendix causing it to stick. Can sometimes be fixed quickly by taking off black cover and squirting something in to clean, WD-40, carby clean etc. Bendix should be taken out regularly to clean. Sometimes has weird whine.
3. Dirty Brushes, connections inside. Good thump will fix. clean to fix
4.Bushes in motor break. Hard fix, starter motor needs to be totally taken apart
5.Connector issues from buttons to starter motor.

Most fixes can be done by anyone, without special tools. It usually just requires a good clean for most fixes. brushes are fiddly


Thanks for the tips Bill! I will be tearing into it tomorrow am!

The two main causes I have had with starters are a bad battery (wouldn’t hold a charge) or bad Brushes. Now I always keep a back up battery and a spare set of Brushes. Brushes are not a fast fix, but not that difficult.

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If you’re not using an AGM (absorbent glass mat) battery then it is likely to fail suddenly, giving either 10V or 13V open-circuit and 0V under any load. I like Yuasa motorcycle batteries, because they’re American-made AGM batteries and meant for hard service. If a karter’s battery goes, an external starter can be used. If a motorcycle battery fails, the rider is left hoping there’s enough voltage and current to run the ignition for a push-start - and then once home the rectifier/regulator is likely to be found dead.

I have a lightweight lithium battery. I will have to test it with my meter when I try to start the kart. Thanks for the tip!

Yiou have been given many ideas to look into. I am curious what you experienced. When you say it would not start do you mean the starter wouldn’t turn or wouldn’t engage?

Nothing happens when I press the starter button. Had it happen once before when a connector came off the switch, but that was obviously easily fixed. I will keep you posted I am going to dive into it tonight!

Joining in this discussion because our starter quit on the qualifying grid over the weekend. Found that the wiring harness shows no open circuits in neither the ground or +12 volts to the starter. Pressing the start button makes or breaks the +12. The starter motor shows low resistance between the terminal at the top and its case. The battery is reading 11.9 volts. Going to run two jumper wires from the battery to the starter and see where that takes me.

Hey Guys! Sorry I forgot to update this! Rushed all week to get this finished up to race last weekend! It was the brushes. Once I took it apart it was obvious!

I even got the armature back in on the first try—but then I looked down and noticed an o-ring that didn’t get put back on!! So took it apart and then it took me 20 try to get the armature back in between the brushes.

In the KA manual there is a good tip for holding brushes in while you place the armature. They recommend using a piece of safety wire in a U shape and it really did work well. Once I had the armature in I was able to use a flatbed to push the brush back on each side just a touch to get it drop in all the way.

I should have waited because it was the worst race day I have had all year! And now this week I am changing out a bent axle.

I have a good feeling it is your brushes in the motor.

If that is 11.9 volts no-load, the battery is no good. Also, check the battery under load, a good battery will read 12V or above. I had an similar experience with the starter system. The battery read 12.7 volts no-load, which should be fine, so we replaced the wiring, the brushes, everything except the battery. We then checked the battery under load and it dropped well below 12V. Replaced the battery and it started. It seems that the KA100 starter system is pretty robust and the battery is the weak link. Since the batteries are cheap, I usually have a spare. The other thing is keep both batteries fully charged. After a race weekend, put the battery on charge and when it is at 100% SOC, take the battery off the charger and disconnect the leads to the battery.

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Justine, having had a pre-09 Leopard, brushes were my first thought but the KA starter has been very reliable.
Larry, because I had a Leopard, I just happened to have a load tester and a spare battery. The spare battery tested great. The battery on the kart read 0 volts under load. Think this one is fixed.

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Larry, there are no old fart karters. Just ones with more experience.

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Just curious how old the motor was that it needed new brushes? Plus do you prime your fuel line before starting or use the starter to prime the line? For something that is used a few minutes per race weekend this seems like premature wear.

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On the KA I always prime it by bleeding it at the carb before I start it for the day. For me it just feels better than cranking on the starter button until it sucks the fuel up.

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