Hi now that is summer in europe i have a question.
Where i go to train its quite hot on summer about 34°c, i train with kz engine and maybe i hit 70°c on the engine when the ideal is 50-55°c, is there much of impact on performance? If so i will plan to buy a big radiator. Thanks
IMO with out seeing or hearing any data (so this is really a guess) I think you should jet a little fatter.
If you can afford a bigger radiator you could do that too.
As for performance, in my opinion, its more about how the engine is feeling while driving, which is a bigger discussion. Making sure the engine is smooth through the rev range not surging or racing at any point.
60 C is what I aim to stay under, your engine may perform best at 70.
At some point the engine will go beyond what is it’s best performing heat range and start loosing power, is that 50c, 60c or 70c? it depends on the local weather conditions and what jetting you are using at the time.
KZ Jetting is a black art.
Yeah you’re leaving a little power on the table at 70c.
Before you go to bigger rad, or a second one, consider the axle/pump ratio for flow and also use a surfactant such as water wetter.
If you feel inclined, you could cowl your current radiator as well to make it more efficient
Also, please update your profile to your real name 
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Hi again, what i felt most it was the kart sometimes made me the ‘‘empty effect’’ on slow speed corners with low revs, it’s maybe caused by high temp?
Yeah it could be if it’s very mild. But for that I think I might look at the needle selection and/or clip position.
Are you tracking air density?
Nope I’m not tracking it but last week I changed the circuit where I will go to train frequently and I noticed that empty effect that i didn’t notice on the other circuit, I know I have the needle on the 4th position and it was the recommended position on the other circuit but I’m not sure it’s the best on the new circuit. It happens on some very closed corners with the 2nd gear the engine drops down, i should put the needle on a lower position like on 3 or 2??
Which tracks are you driving at?
I tend to go rich first if I’m not 100% sure which way to go. So you would raise needle/drop clip.
Another thing… are you sure the engine is staying in the correct RPM range out of those tight corners?
If the power drop off is very significant, where it almost feels like the engine goes totally dead, then suddenly picks up after a few meters, , that is what I would consider first.
Have a look at the min RPM on your datalogger for the turns that are tight.
If the RPM out of the corners is too low, your options are:
Change gearing.
Lengthen exhaust at the flange
Consider chassis may be too “flat” causing the rear wheels to scrub off speed, dropping RPM out of range.
Drive faster 
Hope this helps.
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Keeping the RPM at a decent level when coming out of a very tight corner can be a tricky situation, not so much with automatic engines, but with KZs and especially with the Super Shifter 175cc .
Hey, great advice, “drive faster” 
that’s what we’re all trying to do.
Silly question, but are you sure you’ve bled all the air out of the cooling system? My X30 runs at no more than 45C. I fill the radiator on the stand and then lift the left wheel up to eye level, and will hear the “glug…glug…glug” of the air in the engine draining out to the radiator cap, then add water to fill it and close it up. It’ll run a lot hotter if there’s air in the lines.