Originally Posted by Chris Peralta

Yes the WS series engines, the S5's, S7's, and S3's were all short stroke engines that are no longer produced. The engine that might closest resemble the power the WS9 made might be the Rally10 or the Cross10. The Cross10 was the engine they brought in to replace all the square stroke engines. The Rally10 is not designed for buggy but I have heard that they work great so I have one I broke in last weekend I will be trying out soon.