Highside
Lord of the Flies
Well, after getting my hands on an XS650 cylinder head and taking a close look at it, I can see right away some of the performance restrictions built into it.
The valve angles are too steep, resulting in a chamber that is too large. You can't get good CR's without risking detonation or combustion dead spots (maybe that's why they went with the cast iron chamber inserts?).
The exhaust port is poorly designed. It starts its horizontal bend right before the valve guide, causing bad flow bias around the valve stem. To compensate for this, they made the exhaust valve too big and gave the port too much cross sectional area for the airflow requirements. With some heavy meatball surgery, I bet I can get this port to flow the same, or better, while reducing its volume.
650 Central.com sells a head for $1400 which it claims is the best thing on the market. For that price, you could almost make a custom billet head that would solve the design flaws of the stock head and make 70+ HP with little effort.
Are there any other high performance heads on the market for the XS650??
The valve angles are too steep, resulting in a chamber that is too large. You can't get good CR's without risking detonation or combustion dead spots (maybe that's why they went with the cast iron chamber inserts?).
The exhaust port is poorly designed. It starts its horizontal bend right before the valve guide, causing bad flow bias around the valve stem. To compensate for this, they made the exhaust valve too big and gave the port too much cross sectional area for the airflow requirements. With some heavy meatball surgery, I bet I can get this port to flow the same, or better, while reducing its volume.
650 Central.com sells a head for $1400 which it claims is the best thing on the market. For that price, you could almost make a custom billet head that would solve the design flaws of the stock head and make 70+ HP with little effort.
Are there any other high performance heads on the market for the XS650??