Odd LO206 Issue Last Weekend - Seeking Opinions

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!

I’m not a 206 expert, but the temp as cold (need more fuel), the plug was a little white (need more fuel), you richened it up, and it fixed the problem. Seems pretty cut-and-dried that it was too lean.

Didn’t manifest until part way through the session, once the engine warmed up and started needing more fuel.

Unless I’m not privy to some detail it sounds like you successfully diagnosed an issue and fixed it.

I’ll let the Ghost boys chime in with their expertise.

Thanks for the feedback. I am hoping it was just too lean. But, for some reason I don’t feel like that is it. Would being just one clip position too lean cause a complete lack of throttle response and the engine wanting to die? I am not sure how drastic one position is to be honest. I have also heard that running worse when the engine warms up can be a symptom of running too rich but I could be wrong on that.

The previous time this engine ran was in November under very similar weather conditions and it had no issue (temps in the 40s). I did not change the float height, drop or clip position between the two days.

Additionally, doesnt the main jet needle clip really only impact fuel mix from 10-75% throttle? At full throttle, that is controlled primarily by the main jet. So when I had my foot all the way down and nothing was happening, would the clip position have impacted that all too much? (I am learning hear so forgive me if I am way off).

Your understanding is very good. The clip change may have been helpful, but absolutely would not have solved the problem you were having.

When you cleaned the jets, could you see through the idle jet? 85% chance you had idle jet plugged and successfully cleaned it out when you cleaned the carb. Clean it again at home, flush your tank and start fresh. You’ll probably be good to go!


TJ thinks I have expertise?!?!?! Exciting Day!!!:stuck_out_tongue_winking_eye:


Dunno why I was inspired


I thought there were going to be articles about cam twisting and rib protectors in this issue? :grin:

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Clearly more than me on this topic! :beers:

Listen to Derek, ignore me.

The air density went up, you were nice and lean to begin with, and the mixture dropped too lean to make good power. You can raise the floats to enrich the mixture a little, or you can pull the needle up with the clip, or you can make sure to use a fuel that is vaporizing the whole way at your running temperature - as the race goes on, the tank and the carburetor cool down from evaporation!

Sorry for the confusion. I cleaned the carb prior to the track day Sunday. I meant to make the point that I didnt make a change to the carb settings compared to the prior track day at which I had no issues. All I did prior to this race day was clean the carb.

After the session where it was having problems, I did not clean the carb in the pits. I took it apart, checked the float height and confirmed the jets were snug but I did not clean them. The only change I made was moving the clip from P3 to P4 to richen the mix.

So I guess what I am looking for is a sanity check that:

  1. The behavior of my engine was consistent with a too-lean mix as the source of the issue. and
  2. That moving the clip from 3 to 4 is a drastic enough change to completely rectify the issue and run well the rest of the day.

It sounds like you are not convinced it was just a matter of moving the needle clip and neither am I. Another data point, I pulled the plug yesterday to inspect it and it is definitely more black than neutral. So, I don’t think the air/fuel mix being too lean was the original issue as the plug now shows signs of being slightly too rich after the clip change.

Its just weird to me that it ran okay (but not great) for a few laps and then all of a sudden crapped out. If it was a static issue (like an air gap between the carb and the manifold, throttle slide stuck, bad fuel, clogged jet), I would have expected there to be more problems right from the start. I also did not change out the fuel in the tank. When it ran fine later in the day, it was on the exact same tank of fuel as when it had issues.

So just to confirm, the sound the engine was making and total lack of revs once it really started to die sounds pretty typical of a too lean mix?

Curious about the fuel comment. I am actually really unhappy with this last tank of “ethanol free” gas. It clearly has a bit of a green tinge to it and leaves green deposits in the carb after running. Per series rules, I can only run 91 octane ethanol free gas.

I’m sorry for not understanding. That does change things.

You are correct that we are together on our assumption. 1 move on the needle will not allow you to go from stumbling, not running right, to running well. It may gain you a tenth of a hp or a tenth of a second, but a clip change will not “move the needle” (haha, awesome pun, I crack myself up) enough to notice that big of a difference.

I still wonder if there was a partially clogged jet? Maybe opening the carb and checking everything was enough to let whatever was wrong fall out?

P.S. Reading a plug on a 206 is not straight forward. Lean does mean lean, but rich does not mean rich. Due to the tune that most top guys run, the engine is extremely rich off throttle. So, it is almost impossible to read the plug after a cooldown lap or after putting into the pits.

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Thanks for the additional information. At this point, it sounds like there was just some fluke of a problem that I unknowingly resolved by taking it apart and re-installing it. I was hoping there was a clear “X was the problem and you fixed it by Y” so I don’t make the same mistake again, but it doesnt look like that is the case.

Thanks for the help!

Would you eat old stale food that had turned green? If not, why would you feed it to a racing engine?

When I ran 206 I bought fresh fuel at the pump every day, and poured any leftover fuel into my car’s gas tank.

Well actually… if the mold can be scraped off, it’s all good.

French cheeses can be pretty wild, too.


The problem isn’t the ingestion/combustion phase… it’s what comes out the exhaust that’s alarming.


No I get that. Its what I had and it was supposed to be “clear gas” but you are right, I should put it in the car and get fresh next time!