Hi All,

I recently bought a lightly used 2013 KFX 50 for my son. Since I bought it, it will start, run and take off but after about 20 or 30 seconds will bog down and not move. You have to keep your thumb in the throttle just to keep it running. If you let off at all it will die and is very hard to start. I've replaced the carb as the old one was gummed up and had some issues. I have also replaced the ignition coil and still have the same issue. I am leaning towards it being the CDI box?

When I research this box online, they are everywhere but are AC rather than the DC I need for this machine. Any help here?

Thanks!

Biekdawg

 

Check that you are getting a good flow of fuel to carb and the tank vent isn't blocked. If your new carb isn't genuine, it may not be set up for your engine and may even have the wrong jets. Change the plug if you haven't done so already. Check the regulator isn't overcharging when engine is running, more than 14.5v across battery terminals and it will slow cook a DC CDI. Better to get a workshop manual and do the electrical tests in it, rather than keep buying new components, because it is as likely to be a trigger coil problem as a CDI one.

 

All good things to check. Every replacement carb I have ever bought had the wrong jets in it. But that shouldn't cause the problem you are having.

In addition to that, Just a couple questions, So it runs the same with the new carb as with the old carb? Or is it different.

You said it bogs down and will die if you don't keep your thumb on the throttle. Is it smoking out the exhaust? Like flooding the engine with fuel rather than starving it?

Does it run better or worse with choke on?

 

Check the valve adjustment

 

Thank you all for the advice. I appreciate it!

It seems to be running very rich when you keep your finger in the throttle and it starts to bogg down. Has a very strong gas smell out the exhaust when that happens.

I will check the voltage to see if there are any issues there. I have red that many of these smaller ATV's and scooters with this same engine have rev limiters or restrictors that work electronically by cutting out the spark to limit the engine. Could that possibly be the issue for the motor running very rich and bogging out?

 

I suppose it could be. You can get an inline spark tester from places like harbor freight. Put it on and leave it.

That allows you to keep an eye on the spark when it is running. Might tell you if you are losing spark or not. If not then you have a fuel issues. If so then electric. Like a CDI issue.

 

Did you check choke operation?