X30 Freshen Up time?

Before the new season kicks off we were planning to send my son’s X30 off for a fresh top end, but before we do I’ve popped it apart to measure up and check the general conditions.

The engine was bought second-hand, so not sure exactly of the rebuild history, but we believe that last was a full rebuild approx. 6hrs before we got it. Since then it has done 5 race meetings and some practice, so potentially ~12hrs.

On this basis, I was expecting to find it pretty worn and piston clearance to have opened right up…
What I found :

  • Squish was 0.9mm
  • A fair amount of carbon build-up on the piston crown
  • Piston Measure: 53.92 (Couldn’t see any sizing marked)
  • Bore measures: 54.04
  • Cross hatch still visible in the bore
  • Ring gap: .025
  • Clearly has had a full rebuild before, based on the witness marks in the crankcase it has eaten a piston or broken a rod previously.

Pics attached for information.

I’ve not rebuilt one of these before, with engine-work experience limited to bikes and cars, so was a little unsure of what to expect.
My first reaction after taking measurements was that it looks fine to pop back together and go for several more hours - but that just doesn’t align with normal service intervals.

Collective KP engine brains trust, what do we make of the condition as found?

I’m not the X-30 expert here but have run X-30, KA100, KPV and Leopards. Maybe, some others will chime in. I wouldn’t go past 12 hours on an X-30. Your motor reputedly has 12 hours on the bottom and part of these hours are in question. So, if were me, I’d rebuild the entire motor.

Also, look at the rod crank bearing condition, that might drive your decision.

There is also fresh discussion on piston clearance on KP, that might be informative. Also, there is likely a discussion on the rod crank bearing on KP.

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+1 on the above. Especially with used engines of unknown origin and since it may have 12 hrs on it already, the safest thing is a full rebuild. From the picture I can see the piston wear and some blowby allround so for sure top end. Bottom have it done for safety, you may be able to reuse the rod and just change bearing,pin and spacers so it may not be that big of a deal cost-wise. If you need a new rod too, you at least catch it in time

Holy that first picture makes the engine look dead. Normally you send a 2 stroke (mini, micro, junior, senior, etc.) in every 4-8 hours. I normally send mine it at 6-7 hours on runtime, but I do know some people that send it in crazy often.

Is this your first time sending it to a builder to get it rebuilt? How long has it been run?

Of course, not a huge X30 expert seeing as I drive a swift.