If you’re looking to upgrade the crankshaft on a CG250 to a CG400, this guide is perfect for you. Below, we’ll walk you through the step-by-step process to improve your bike’s performance and get the most out of the benefits of this upgrade. The crankshaft is one of the most critical parts of the engine, and upgrading it can make a huge difference to your bike’s power and reliability.
The main motivation for upgrading from a CG250 crankshaft to a CG400 crankshaft is the significant increase in power. Not only does this improve your bike’s ability to handle heavy loads, but it also allows for higher speeds and climbing steep terrain with greater ease.
Upgrading a crankshaft is a great way to get the most out of your bike’s potential without having to completely replace the engine. If you’re a dealer or wholesaler with stock of unsold CG250 crankshafts, this modification can be a great way to give them a new lease of life. The demand for faster, more powerful bikes is on the rise, and the CG400 crankshaft is the perfect answer to meet that demand.
In order to increase the displacement from 250cc to 400cc, it is necessary to extend the stroke. This involves increasing the crankshaft pin rotation radius. A larger radius results in a longer piston stroke, which generates more power. This is one of the most important steps of the upgrade, as it has a direct impact on the overall performance of the engine.
A customer from Argentina shared with us his experience when performing this upgrade. His bike experienced a substantial improvement in power and performance on rough terrain, especially when he compared his bike’s performance to the standard CG250 version.
The standard CG250 crankshaft tends to fail under high stresses, which can affect the long-term durability of the engine. Therefore, we recommend opting for a forged steel crankshaft. This type of crankshaft is much stronger and can withstand higher revs without the risk of failure. A forged crankshaft ensures that the engine remains stable even at high revs, which is essential for riders looking to improve their bike’s performance.
In our testing process, we tested the forged CG400 crankshaft at over 11,000 RPM without any issues. A customer in Brazil who used this forged crankshaft mentioned that his bike improved considerably in terms of reliability and longevity.
A longer stroke will cause the piston to move more, which increases vibrations. To resolve this, the crankshaft needs to be rebalanced.
Also, a longer stroke requires shorter connecting rods. If the connecting rods are too short, the piston could hit the cylinder head. If the connecting rods are too long, the compression ratio will be reduced. We have determined the optimal connecting rod length for the CG400, ensuring power and reliability.
Once the crankshaft has been upgraded, it is critical to perform rigorous testing to ensure everything is working properly. This includes dynamic balance testing and high-rev operation. Our testing process includes the following:
- High-rev operation for 48 hours.
- Temperature cycling from -20°C to 150°C.
- Dynamic balance testing.
These tests ensure that every crankshaft we ship is ready to run efficiently and safely over the long term.
A longer stroke will cause the piston to move more, which increases vibrations. To resolve this, the crankshaft needs to be rebalanced. In addition, a longer stroke requires shorter connecting rods. If the connecting rods are too short, the piston could hit the cylinder head, while if they are too long, the compression ratio will be reduced.
Finding the optimal connecting rod length is crucial to ensure maximum power without sacrificing reliability. At Ruizheng Racing, we have spent time and effort determining the ideal length for the CG400 crankshaft, and our customers have experienced tangible improvements in stability and performance.
A distributor in Brazil always prepares for the peak season in October. Last year, he faced the dilemma of ordering CG250 or CG400 crankshafts. After testing our CG400 conversion, he decided to upgrade his surplus CG250 inventory. This approach allowed him to increase his profits.
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