Polyisobutylene (PIB)-based deposit-control additives are polymeric substances that function as additives in engine fuel to prevent gum and sludge formation in the combustion process and reduce the release of impurities associated with severe performance and environmental issues. This work synthesized two types of additives by modifying polyisobutylene with diethylenetriamine (PIB-DETA) and pentaethylenehexamine (PIB-PEHA). We performed characterization using Fourier transform-infrared (FT-IR) spectroscopy, UV-vis spectrophotometer, thermogravimetric analysis, and liquid chromatography-electrospray ionization-quadrupole time-of-flight-tandem mass spectrometry (LC-ESI-QTOF-MS/MS) to evaluate the chemical properties of the products. The generation of intake valve deposits (IVD) and combustion chamber deposits (CCD) were observed to ascertain the performance of synthesized dispersants to control deposit formation in the motorcycle engine. The results showed that PIB-DETA has better performance to control CCD generation than PIB-PEHA in IVD. Compared with commercially available PIBA, these two dispersants have less different performance and are potential for industrial application.