The Ruifeiya inline four cylinder engine is an improvement based on the NR200. The Ruifeiya inline four cylinder engine is equivalent to two NR200s. Due to the short crankshaft of the NR200, the crankshaft support issue was not considered in the design. The inline four cylinder crankshaft is relatively long and needs to be considered for support. I have seen other inline four cylinder engines made by peers, including those without support, those using bearings, and those with copper tiles. An unsupported crankshaft cannot withstand the impact force and centrifugal force of piston explosion, which can easily lead to crankshaft fracture. Using bearings requires increasing the crankshaft chamber, weight, and volume, and the machining process of using bearing shells is complex.

After considering three factors, we wanted to take a different path and searched for various engine discoveries in the market. We found that Yamaha used excessive body bearings to install connecting rods. Inspired by this, we innovatively used split needle roller bearings on the inline four cylinder crankshaft, while the connecting rods continued to use bearing shells.

We searched in the market and found a manufacturer willing to help us customize split bearings. Based on the customized bearings, we designed the support structure for the straight four engine and mass-produced it on a small scale. After testing, we found that with the help of needle roller bearings, the engine remained stable at high speeds without excessive vibration. This scheme is a bold attempt in the model and also accumulates relevant experience and technology for later engine design.