KZ Shifter - Cost of ownership

Introduce a bad engine, and you’ve added one more engine to the mix until it fades away.
Introduce a good engine, and it’ll kill off a couple of bad engines it competes against.
I think we’ll be in the second camp but the sales, the track results, and the MTBF will tell the tale.

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I agree karting has too many motors but I actually applaud the effort to build a cheaper lower power reliable and consistent shifter package. I think the Restricted ROK is already a great option but honestly something even less powerful you could run on a harder tires rear brake only to use TAG chassis would be even better. Just check out Norcal, where they have 23+ drivers showing up to race 80 shifters, separated into the main group and “novice” class for guys starting, despite the cr80 kart packages being bit of a PITA to run and require some work, but it’s growing like mad anyway and they’re having a ton of fun.

If it’s a 4T I’m interested. 2T, I’m not sure the juice is worth the squeeze if it’s making less power than the likes of a ROK or Stock moto.

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I disagree with that. My 80 has been sitting since September and I could go put fuel in the tank and it’ll fire first spin with a one handed roll of the tire. It gets dusted off once or twice a year for a race and performs flawlessly. :man_shrugging:t2:

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Any thoughts on the wear and blow-by staining below the ring?

TM R1 piston with 2.5 hours. Last race it overheated to about 160 on water temp (darn driver) but no noticeable loss in power. Location of staining looks to coincide with the exhaust port bridges which is where I would expect the cylinder to lose its circularity first when hot.

Definitely not ideal but is this typical for the amount of time regardless of the temp or is it a replace without question due to my lack of attention?

Replace without a question, what did you set the ring gap to?

TM has been offering reduced maintenance KZ engines since the K9ES debuted back around '07, & continues with the KZ10ES:

Rebuild intervals (based on fuel consumption):
Top end @ 100-140 L (26-37 gal)
Crank bearing @ 400-440 L (105-116 gal)

Also has a starter.


As for the piston above I agree replace for sure, but this is not normal, you need to understand what happened. It would help to know ring gap, why it overheated (e.g. forgot the curtain up or out of coolant? jetted too lean?) Look at my piston up above after 6 hours, barely any blowby visible. You also have a fair amount of wear on the skirt for 2.5L.

For the KZ10ES, that’s a lot of run time, basically double the interval! @WheelSpin : do you know how it compares to the 10C/R1 power wise? I know it’s de-tuned but not by much

Don’t know how all the metrics compare (although they have the same published HP ratings), but on a technical course, like I’ve often seen at the SIMA facility, the difference is academic, & more about the driver (no surprise).

Got distracted after a restart and forgot to pull the curtain down. Motor was as delivered (stocker-not factory prep) so initial ring gap was unknown. Also still need to check squish and timing FWIW.

Jetting was pretty conservative but road racing does spend a lot of time at high load so I assume that also contributed.

Overall I’m impressed that I didn’t have more problems. Temp came down once I caught it and was still pulling the same MPH at the end of the straight.

Oh yeah, that’ll do it. Yes change piston and needle bearing and you’ll be ok then. Inspect the cylinder wall for marks, but it should be ok.

Going forward, you can use your mychron to help…I’m using a blue light in the left for cold, goes away when engine is in temp range. Then I use the other one on the right, red when getting hot, blinking when over the max, at that point if I can’t get the temp down quickly, I stop

Had a light set up and I still missed it…

Guess I was having too much fun. Can’t fix that

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I think we’ve all been there! Glad it’s not bad!

I use a red solid light for overheat and a magenta flashing light for EGT over limit. The only other red light I have on my display is the last “ok, you’ve gone way too far” shift light so the overheat light is the only solid red on there.

not to derail thread, but yeah I absolutely love my 80, i just find they require a bit more attention than stock honda or restricted ROK, and new piston every 3.5 hours (albet piston is $65 and you can do them in 15-20 minutes) but yeah the cr80 package is still a ton of fun and blast to race on hard tires.

4h on piston and 0.35mm ring gap. Barely any wear at all, runs on aspen 98 with 4% motul 2t oil!
Vertex piston, 53.93


Looks super clean! Have you had to tweak anything with the Aspen fuel in terms of jetting, advance or other parameters?

It is almost the same as normal pump gas. It has lower density so slightly more fuel is needed. But when running too rich it could pop sometimes, but the quality is excellent so zero problems. Ran it the whole 2022 season as it became mandatory :grin:

Never leaves residue and I didn’t need to change timing. Running 1.1mm squish, 4 degree piston

I’m assuming F here,160 is nowhere near overheating. It’s not optimal, but definitely not overheating.

I’d sometimes see temps around 150/160 in road racing too. It’s not a cause for concern, but if you can get to 130 that’s not a bad thing.

160F. Running a big radiator, keeping it at 120 has not been an issue. (other than driver forgetting curtain). Usually have more of an issue getting up to operating temp, especially if it’s cold out.

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