Tuning the X30 engine on track

2 Stroke Kart Engine Forums
1

Hi guys, I’m new to the X30 engine and was wondering about tuning the carby while on track.

I used to race the Yamaha KT100s (or Clubman) aircooled engine many years ago, and it was normal to tune the High needle while driving, to achieve certain engine temperature as the race progressed, but also to lean it off on roll-up laps as to not foul the plug and get a crisp get away off the line.

I’ve been told with the X30 to set the Low jet at 1 turn open, and the High jet at 1.5 turns open and don’t touch it at all while on track. But I noticed a couple more experienced competitors tuning theirs on the roll-up laps of a race. What’s the general rule you guys follow? Cheers.

2

I definitely remember our regional hot shoe, Bonanno twiddling the dial on track back when I raced x30. Similarly to what you observed, on warm ups.

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3

You can dial in the carb a bit on track, aiming to get your EGTs in the correct range but overall it isn’t as drastic of a change as it would’ve been on a KT. Engines these days are more foolproof in that regard but it is still a valuable skill for eeking out the last little bit of time from the motor.

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4

Just stay on top of maintenance and it is foolproof. I like to richen up things a bit, I often find good success with low needle in 1:05-1:10 and high 1:30-1:35

Keep membranes in good shape and check reeds and you are good to go

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5

With the needle setting being dependent on the popoff pressure… What popoff and hold pressures are you running?

6

I found it very difficult and risky to adjust the carb during a race on either the X30/KA100 because of the sensitivity of the needle settings, measured in
“minutes”. I treated it like a float carb and made adjustments in the pits after reviewing exhaust temp data. The X30/KA100 carbs are a dream, when compared to the KT-100 carbs. Like TJ pointed out these carbs really don’t require much change once they are set correctly. I’m sure time could be found by tuning the carb on the track but there are more areas that are more productive in reducing lap times, unless the carb is not working.

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7

Always ran with the standard spring, it opened at 0.7bar and held steady at 0.55bar.

Tried the 42g spring but the higher pressures was never needed

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8

on our x30 super 175cc single speed engine we found that 42g spring was making things more alive overal . with this pop off opens at 10psi and holds steady at 8psi .

but 175cc is a different animal thats for sure .

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9

I wasn’t so much looking to eek out better lap times but moreso looking to possibly lean it off on the roll up lap where everyone is crawling, to get the best possible get away and avoid fouling the plug. But if it’s generally accepted that this isn’t necessary then I’m happy to not have to touch it.

10

It’s not necessary. If you want to experiment you could play around with the ole Rotax “pinch the fuel line” trick, but I’m not sure it would translate to any benefit. When I ran X30 I didn’t mess with the needles when rolling to the start line.

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11

I mean, one can do it, it just requires a very good ear to hear the engine and experience on track

12

The ultimate way to know is to test it on track with a simulated start. I’ve heard very conflicting things on leaning or richening across engine packages.

I’m skeptical leaning out the engine on a start is a prudent idea. That said, you can definitely foul a plug if you try hard and believe in yourself in a modern engine.

13

Go watch X30 starts at the high levels and you’ll rarely see people touching the carb. It just doesn’t really do anything on these engines.

I’ve tried leaning it down and pinching the line like Evan mentioned and neither made a noticeable difference.

Sometimes I like to lean it down for a second after the warm up lap and give it a few revs to clear out any unburnt fuel from the fast warm up lap, but again, not a noticeable difference to acceleration.

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