Since 1980, the production of the Izh Jupiter-4 motorcycle with an engine began, the power of which, compared with the previous model of Izh Jupiter-3, was increased from 25 to 28 liters. from. The motorcycle received a new carriage with a shield attached to the fork, and not to the traverse as in the previous model. Also, a fundamentally new 12-volt electrical equipment began to be installed on the motorcycle, which, together with the new larger diameter headlamp, increased the safety and comfort of the driver and passengers. Of the minuses of the design, a large number of terminal connections in the motorcycle wiring can be noted, due to the frequent failures of various components of electrical equipment. The engine has a weak crankshaft, which was improved in 1983. Compared to the third and fifth models of the series, the engine has higher rpm of maximum power, which in the absence of high-quality lubricants led to rapid wear and failure of parts of the cylinder-piston group of the motorcycle, in addition, it shifted the maximum torque to higher rpm, which is bad affected the performance of the motorcycle when used on rough terrain. In view of the fact that most of the motorcycles were used specifically for use as an “enduro,” in subsequent versions, motorcycles of this series lost part of the horsepower for the sake of shifting torque to the lower speed range, and increasing their production resource.
