Yes, having sand in the crankshaft is bad for the engine. Sand can cause abrasion and wear on the moving parts of the crankshaft, leading to potential damage and decreased engine performance. It can also cause blockages and restrict the flow of oil, leading to overheating and potential engine failure. It is important to ensure that the crankshaft and other engine components are free from sand and other contaminants to maintain optimal engine function. **

You will need a new cartridge that is compatible with the Dual 721 turntable. The original cartridge for the Dual 721 is the Shure M75-6, but since it may be difficult to find a new one, you can consider a suitable replacement such as the Audio-Technica AT95E or Ortofon 2M Red. These cartridges are known for their compatibility with the Dual 721 and will provide good sound quality for your turntable. Be sure to check the compatibility and installation instructions before purchasing a new cartridge for your Dual 721 turntable. **

A kickstart crankshaft is designed to be manually started by using a kick lever, requiring physical effort from the rider to start the engine. On the other hand, an electric start crankshaft is equipped with an electric starter motor that allows the rider to start the engine with the push of a button, without the need for physical exertion. Electric start crankshafts are typically found on more modern motorcycles, offering convenience and ease of use compared to kickstart crankshafts. **

The crankshaft slides horizontally through the use of bearings and lubrication. The bearings are placed at specific points along the crankshaft to reduce friction and allow for smooth horizontal movement. Additionally, lubrication is applied to the bearings to further reduce friction and ensure the crankshaft can slide easily. This horizontal movement is essential for the crankshaft to transfer the up-and-down motion of the pistons into rotational motion. **

The crankshaft can be filed by using a precision file to remove any burrs, nicks, or imperfections on the surface. It is important to use a file that is specifically designed for metalworking and to work carefully and methodically to avoid damaging the crankshaft. The filing process should be done with the crankshaft securely held in place to prevent any movement or flexing. After filing, the crankshaft should be thoroughly cleaned and inspected to ensure that the filing has achieved the desired result. **

The original crankshaft may or may not be able to handle it, depending on the specific circumstances. Factors such as the engine's power output, the type of modifications being made, and the condition of the original crankshaft will all play a role in determining whether it can handle the changes. It's important to consult with a knowledgeable mechanic or engineer to assess the crankshaft's capabilities and determine if any upgrades or replacements are necessary. **

The RPM (Revolutions Per Minute) of the crankshaft is a measure of how fast the engine's crankshaft is rotating. The RPM of the crankshaft can vary depending on the engine speed and gear ratio. In a typical car engine, the crankshaft RPM can range from around 600 RPM at idle to over 6000 RPM at full throttle. The RPM of the crankshaft is an important factor in determining the engine's power output and performance. **

The crankshaft gear can be saved by ensuring regular maintenance and inspections are carried out to detect any signs of wear or damage early on. It is important to use high-quality lubricants and ensure proper lubrication to reduce friction and wear on the gear. Additionally, avoiding excessive loads and sudden changes in speed can help prolong the life of the crankshaft gear. If any issues are detected, it is important to address them promptly to prevent further damage and ensure the gear's longevity. **