Jetting Investigation

I’m investigating the topic of jetting richness in relation to engine heat and lubrication and think the karting world is a good place for data gathering since your setups and type racing are extreme. I’m mostly from the motocross world and so don’t know much about karting setups. Could you do me the favor to answer these questions?

  1. Do karts have rich jetting compared to motocross bikes?
  2. Do the majority of karts use synthetic or castor/synthetic engine oil?
  3. What is the color of your piston underside? (Please tell the engine oil used, fuel/oil ratio, and type of engine cooling (water or air)

Michael, it sounds like you are asking about 4-stroke engines due to the question about engine oil. Most high hp kart engines in the karting world are 2-stroke, and in the US, high octane leaded fuel is still used (due to the Honda 80 and 125 motocross engines that used to be dominant).

What type and size engine, with what fuel are you looking for answers to?

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He means two strokes.
It’s hard to compare Mx and Karting because the engines end up in a very different config on a kart.

Stock Honda for example (CR125) runs a very aggressive pipe compared to the MotoX version, along with plugged power valves. I suspect we feed them more fuel in karting, but I’m not sure if they run any richer in an AFR sense.

I’m disappointed to not get even one of the 3 questions answered, just people asking me questions as if I didn’t make it clear I am investigating the topic, not trying to figure out a problem I’m having…
It’s like here in South America the habit of the salesmen is to ask you what you want something for which is infuriating so I often say “I’m working on a space ship, now just get me what I’m asking for (such as a multi-purpose crescent wrench)”. Then if they get pissed off in return they say something like “we don’t sell tools for working on spaceships”. arghh

Part of the problem is the premise of question. There is no single answer that represents karting.

Karting comprises of a lot of disparate rulesets and engine packages. Piston port, reed, rotary. Mixing ratios from 50:1 down to 16:1, CDI and analogic ignition. Power valves actuated by port pressure, or electronically controlled. 50cc to 250cc. Single gear and multiple gear. Even different types of racing.

There’s a TON of variables in karting.

At the very least, you’ll need to pick and engine package to compare. Which is why I shared what I know about the CR125

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If a couple people try to be helpful and answer your questions (of which most karters will not know the answers to), and you don’t provide clarification, I’m not sure how you can expect people to help. This is a discussion board, not a demands board.

Most 2-stroke engines are running full synthetic oils, but as James noted there are TONS of different engine packages being raced. His comparison to the CR125 is probably a more apples-to-apples comparison to motocross.

The other two questions, I don’t have a clue.

  • Do karts have rich jetting compared to motocross bikes?

Define rich? Rich by AFR, or simply a larger jet? The latter, yes bigger jet generally. But again with the CR series in a kart, the pipe is much different on the kart application too. So it’s not apples to apples. Also the Cr125 in karting runs a 39mm carb which I don’t think is used on the motocross version?

  • Do the majority of karts use synthetic or castor/synthetic engine oil?

Varies with class, engine package, rules, engine builder. There’s no clear answer other than perhaps Rotax Max which is overwhelmingly synthetic but also not used in motocross. One org even specifies a mix of a 50:50 oil mix castor and synth.

  • What is the color of your piston underside? (Please tell the engine oil used, fuel/oil ratio, and type of engine cooling (water or air)

Can’t help there. I’m colorblind :joy:. I have multiple engines, but none are motocross derived.

Ok…I’ll play since you seem to just want feedback without specifics.

1). Rich
2) synthetic
3) silver - kart engine air cooled

  1. No. We’re running between best-power and stoichiometric. My plug will be light tan most of the time, while a motocross bike will have to run richer because re-jetting is more difficult.
  2. Most people run synthetic/castor blend. I use Klotz Super Techniplate which is a synthetic/castor 80/20 blend, and my engine manufacturer recommends Elf HTX 909 which is also a synthetic/castor 80/20 blend
  3. Grey. Klotz Super Techniplate, 24 fuel : 1 oil, water-cooled.

Running an open questioned questionnaire is difficult I think. Maybe you can create a multiple choice one and send the link.