Ithayimini yezikhali (Ithayimini yezikhali) iyindlela enkulu yezindiza zomshini, ngokusebenzisa ukuxhumana nokunakekelwa kwe-crankshaft futhi nokunakekelwa kwezikhathi zokufaka nokuthuthukisa. Ukusebenzisa ithayimini ngaphandle kwezinkomo kubonakala ukuthi izwi lezikhali liyaphakamisa, ukunakekela kuyathuthuka, isimo sokuqhubeka kwalo kuyaphansi futhi kuyakho ukukhokhela. Ngokwazi, ubude bwezikhali kumele kube ngokuphelele kunokwesibhakabhaka esimbi, ngakho-ke ithayimini kumele iswe ngokuhamba kwemali noma isikhathi esetshenzisiwe ngokwezifakeli. Umsebenzi wethayimini yezikhali kuyokwenza ukuthi isitroke se-piston (ukuhamba phezulu nokuphansi) uma umshini ushaya, ukuvula nokufunga kwevalvu (isikhathi), ukulungisa isizathu se-ignition (isikhathi), futhi ukulondoloza ukusebenza "ngokuhlanganyela" kusukela lapho kunezinkhokhelo zokusebenza "ngokuhlanganyela". Ukusebenza kwezikhali kuyokwenza ngokuhamba kwemikhumbi yomshini, ukuze wonke umkhumbi uhlale: uma ipiston iyaphakamisa phezulu kumkhumbi wesikhombisa, ivalvu liyaphakamisa, futhi ispark plug iyaphakamisa. Ithayimini yezikhali iyindlela yokuhamba nokuhamba, futhi uma ithayimini yezikhali ishaya, ikamshaft ayizakwenzeka ngokwesikhathi, okuyisikhathi kuyakuncitsha ukukhokhela kwevalvu kanye ne-piston, ngakho-ke ithayimini yezikhali kumele iswe ngokwemikhumbi noma isikhathi esetshenzisiwe ngokwezifakeli.