Last weekend was the last Winter Series race this season with the Portland Karting Association. I was last in the kart back in November and the engine felt like it was running well. No issues that I can remember and it was running in a familiar way compared to prior track days.
However, during the first practice session last Sunday, I began to notice that the engine was not hitting the rev limiter where it should and it felt sluggish. Then, a few laps latter it started to die and putting my foot down did nothing (other than keep it running and get me back to the pits). The engine itself mechanically sounded totally fine (no misfires, pinging, crunchyness or anything of that sort). However, it just sort of sounded like it was being starved of fuel.
I took it back to the pits and looked around for obvious issues. Fuel lines look good, fuel filter is newish, pickup is at the bottom of the tank, no signs of fuel leaking at any of the connections. Oil caps are all there, drain plugs are tight, good. My catch can did not have any notable amount of fuel in it and the drain screw was tight. I pulled my spark plug to see if there was any signs of running too rich or too lean. The plug was certainly not black and sooty but also wasnt very white. Maybe a slight hint of whiteness on it. Noted.
So, I figured I best pull apart the carb and have a look. Just prior to the race, I pulled it apart and cleaned the whole thing with brake cleaner. I removed the jets and cleaned those too. I also verified the float height and drop were correct (0.870" and 1.048" respectively). Everything looked good so I put it all back together and re-installed it on the kart.
It was cold out (about 42F) and so considering the slight whiteness on the plug and in an effort of changing at least something before I went to the track again, I moved my needle clip down one notch from 3 to 4 in order to richen the mix. I could not get the engine to idle on the stand. It idled with a slight bit of gas from the throttle totally fine but completely off the throttle it would slow down to 1700 rpms or less and then die. I tried adjusting the idle mix and idle speed screws all over the place and nothing really seamed to resolve the idle issue. But, races are not won idling right? So I headed back to the track.
For whatever reason, I had ZERO issue the rest of the day. The engine was hitting the rev limiter in the spots that I expect it to and it felt like it was back on power. I even had more top end than other LO206 karts the rest of the day.
I am at a complete loss about what happened. Thankfully, I have the first session on video so hopefully you can see and hear what happened as it was dying. I’ve never ran this engine at the 4th clip position before but it seemed to run okay. Is there something I am missing or things I should check out? Was it just bad luck? I am new to the sport but have been trying to do my homework and I can’t pinpoint the most likely cause. I want to know how to avoid whatever went wrong in the future!
Video is below. Engine issues start at 3:45. Thanks in advance!