Zongshen Sierra 200GY-2 Crankcase Cover Mod

[SpudRider]

The 196cc engine of the Zongshen Sierra 200GY-2 is a very close copy of the Yamaha TW200 motorcycle engine, with one major difference. The Yamaha TW200 uses a very fat rear wheel; therefore, the Yamaha employs a very long countershaft that must be supported by a bearing in the left crankcase cover. The support for this bearing is located inside the yellow circle shown in the photograph below.



In order to support this extra long countershaft and bearing, the left crankcase cover is a solid unit. Therefore, if you wish to inspect, clean or replace the countershaft sprocket, you must first remove the entire left crankcase cover. Also, if you wish to inspect or replace the countershaft oil seal or gearshift lever oil seal, you must first remove the entire left crankcase cover.

Since the front half of the crankcase cover contains engine oil, the crankcase cover employs a gasket. Therefore, removing the left crankcase cover always involves the loss of some engine oil, and it could damage the gasket.

The Zongshen Sierra 200GY-2 copies the Yamaha crankcase cover very closely. The outside of the left crankcase cover for the Zongshen 200GY-2 is shown in the photograph below.



The Zongshen Sierra 200GY-2 is not an exact copy of the Yamaha TW200. One major difference is that the Zongshen motorcycle employs a narrower rear tire than the Yamaha TW200. Therefore, the Zongshen uses a shorter countershaft, which does not require the bearing or its support.

I like to remove my Tsubaki 428HQR drive chain at every oil change and scrub it with kerosene. After I dry the drive chain, I then soak it in the used engine oil before I reinstall in on the motorcycle. Removing and replacing the drive chain is possible without removing the left crankcase cover, but it is a bit of a nuisance. I wanted to be able to reinstall the Zongshen’s drive chain more easily; I also wanted to be able to clean and inspect the countershaft sprocket without having to remove the entire left crankcase cover. Therefore, I decided to modify the Zongshen 200GY-2 left crankcase cover.

First I ordered an extra left crankcase cover from Zongshen America. After the crankcase cover arrived I examined it; I determined that a single saw cut could separate the front and rear sections of the cover without compromising the oil seal in the front. I took the crankcase cover to a local machinist, and he made the section shown below.



I can now remove the rear of the crankcase cover without disturbing the engine’s electrical system mounted in the front of the crankcase cover. I can also remove the rear section of the crankcase cover without the risk of damaging the engine gasket, or losing engine oil.

I will replace my original left crankcase cover with the modified cover when I make my next oil change.



Spud