Fuel/Oil dripping out of X30 old-style exhaust flex (n00b kart owner)

Kart owner n00b here. X30 old style. Engine had top end rebuilt just before I got it. First time running as owner / own mechanic. I’ve tuned EFIs before, but never carbs. MyChron is 1T and I had it monitoring water for first shakedown runs.

Mixture is ~5%. 1L Motul 2T into 5gal (18.9L) of Sunoco 260GTX 98 Unleaded. 1:19 Oil to Fuel, 1:20 Oil to Total

Carb set to Fox + Son suggestion of
Low @ 1hr 10min
High @ 1hr 30min

I had it running on the stand for about 5 min on and off dialing in the idle screw. Then we noticed the spew. I pulled the spark plug and it was wet.

I was concerned I’d be spewing onto the track and fellow drivers, so I asked a few experienced X30 guys who graciously took time to look at it. They told me my engine was fine, that this is somewhat expected at idle, to get some flex insulation to keep it contained, but wipe it down and then just run it.

On track, not smoking. Ran great on top, a little throttle delay out of some corners, so I think low speed needs to be leaned, at least.

My plan now before next outing this weekend is:

  • Full carb rebuild just be be sure, pop-off pressure check
  • Add Insulation to exhaust flex section
  • Add MyChron expansion and tune in with EGT. Wideband later.
  • Potentially go to new style exhaust to eliminate the exhaust flex tube

Some questions:

  • If this is expected, should I just never be idling the kart?
  • If this is expected, should I prefer to not run it too long to let water temp get up and just do that on first laps?
  • If this is not expected, what should I be checking?

Thanks all.

Totally normal, especially when just idling on the stand. It is a race engine, it was to scream at high RPM, and should be tuned for that. The excess oil will burn off when you’re under load. It’s fine to let it run at low RPM on the stand to warm it up, you just have some excess oil from the exhaust then. Not going to hurt anything, other than make a little mess.

Wrap the flex area and that’ll solve like 99% of the oil spewing. But yeah, without that wrapped it’d going to coat the whole back of the kart, and that’s pretty typical.

And note that as a race engine, it shouldn’t really be set up to idle without some throttle input. It might a little; every engine is a bit different, but generally it should need a bit of throttle to stay running. Idle isn’t a concern, mixture at 16k RPM is the the main thing to consider.

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Seeing as you have old exuast and ignition - Do you have a Tillotson, or orignal (pre 2108) Tryton carb?

@dar53 Tillotson HW27A. Engine and kart were new in 2021, apparently right before the swap over to the new style exhaust and ignition?

I realized the Fox + Sons suggestion is for the Tillotson and the suggestion in the IAME X30 Assembly Manual at IAME USA East Site and IAME USA West Site is for the Tryton. I could see that messing some people up, so thank you for asking!

@tjkoyen Thank you, that helps a lot!

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The goop coming out is pretty normal as a lot of raw fuel (with oil of course) escapes out the exhaust port at idle and small load.

Once the engine is in its operating range, the expansion chamber in the pipe helps keep this charge in the cylinder more effectively.

Same with the spark plug, they are very cold plugs (NGK 9,10 and sometimes 11) and will foul easily if the engine is not run hard enough to get them into self-cleaning temperature range. Roughly 500C

There’s really very little to be gained with Lambda/AFR. EGT is generally the way to go with two strokes. I totally get wanting to run one out of curiosity though.

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Lambda are good but for one practice session after taht they need to be cleaned good coz the oil on them makes them go crazy

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I’m using unleaded fuel, so it would be just oil right? Would degreasing (oven degreaser or other solvent in an ultrasonic cleaner or similar) revive them?

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yes it does . i am afraid to put them in the ultrasonic cleaners , better work them by your hand .

cleaning works . but as i said lamda is not manufactured to read and live inside of 2 stroke fumes so it will die soon or later as you use them on our smokers .