Cheating up the tach


Last night I was checking tachometers on the predator class when they came off of the track. I have not been putting them on the stand to check the RPM unless they do not have a tack on them. I was informed by a gentleman that races in the southern part of the United States at different race tracks that people are now starting to cheat the tack. That would mean that each time we have to put the cart on the stand to check the RPM 5500 limit. Is there anyone out there that knows any truth to this.


Mohawk Dawg
I'm not surprised. The hardware is not easy to manipulate but you could definitely play with the software with the right tools and know how. Wouldn't take much to manipulate the system that measures your rpm.
Changing the rpm multiplier in the firmware should not be that hard. I would assume with a older firmware would be easier.
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I was using my micron 4 but thought it easier to just read their tach. By doing that I can keep an eye on just how often the rpm keeps increasing thus making it time to look at things. Last night I was told they were cheating up the tach do now it's back on the stand we go. I don't like that


I will call digitron and get the lowdown. Wouldn't you think the cost of such a thing would be expensive?


I do know that you can get a lower rpm reading if you hold the gas pedal down verus the throttle linkage at the carb.
The other thing is the track needs to do it the same way for everyone every time.
Ive been dq'ed for 100 rpms over. No complaints I pushed the envelope.


I have a mychron 5 and was getting reading of 4500 on my stock motor when I was suppose to be turning 6500 or so well I sent it to mychron and somehow the rpms were set to 6000 on the tach well when it went over 6000 it would loop back around and start over at 3000 which is why it was giving me such a low reading. I hope my explanation makes sense


Site Supporter
Don, you should know that you tech each competitor with your own gauge (not the one on their kart.)
Calibration is not that difficult and it IS being manipulated.
Even without fiddling with the calibration, from one gauge to the next can vary a bit...That's enough for me to not use the competitor's gauge for tech. No-brainer -- Kinda like using the competitor's no-go gauge (if he has one) in your tech barn.

And before you dig up an old Mychron 3/4 to use in the barn, get ready for the crying that it's not recently calibrated.
Besides, what's another $4-$500 for another tech gauge, right? ;)

🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN


Seems it could be manipulated pretty easily at least according to the Mychron 3 manual I have...


pretty sure thats for setting warning lights and not a max read value?
No sir, I have messed with mine and it will change the RPM readout on the display depending on the multiplier you select, but this is on the older M3, not the newer ones as I don't own one to test.


Thats how they are doing it, connect resistors/capacitors of different ohms between the plug and the tach, no need to mess with the software
im not sure if it is actually that easy, i have messed with that kind of stuff before. Not on karts or anything, just trying to make a tach work with engine it wasnt designed for (2 stroke vs 4 stroke, oem tach kinda stuff, i dont remember the exact details)

tachs count the number of voltage spikes, they dont necessarily care about the height of the spikes (which is what resistors or capacitors would change) as far as i understand. correct me if im wrong