Here is the AIRSAL 70cc liquid-cooled big bore kit with cylinder head for MBK 51 / Motobecane AV10. This AIRSAL T6 is a T6 model because it has four intake ports and a two-part exhaust port, and it is made of Nikasil-coated aluminum. Its intake port timings are quite low (around 118° depending on the squish clearance and cylinder head type), and the cylinder has a bridged exhaust port with a relatively low port timing (around 162°). A very pleasant surprise: the bridged exhaust port has a factory-applied material correction! The piston is a single-ring design to minimize friction.
We still regret the significant lack of attention paid to the skirt and other aspects! However, let's be clear, this cylinder is designed to produce a robust, torquey engine at a very low price. A skilled tuner can still extract some truly astonishing performance from this cylinder by modifying the port timings, exhaust port shape, skirt, etc. The 118° intake port timing leaves considerable room for improvement on the exhaust port by raising its port timing to gain power and higher RPMs, especially when combined with a good exhaust like the MVT SP3 70, or even for a more subtle approach with a good MVT SP2 exhaust!
We recommend the following with this cylinder : 17mm carburetor, reinforced crankshaft and bearings, expansion chamber exhaust, grade 9 spark plug, crankcase alignment.
The pack contains :
Notice
4-port cylinder with 47mm diameter exhaust bridge, liquid-cooled
Single-ring piston
Piston pin
Segments d.47 x 1.5mm
Complete gasket set
Crab-type piston clips
As an option, we offer a Stage 1 preparation. This includes selecting the best part from our stock, significantly improving the shape and exhaust port timing, and a special modification of the skirt and piston based on our best tests. We recommend port timings of around 118°/178° depending on the squish clearance set by the end user. We suggest a 0.7mm squish clearance and a 13.5:1 compression ratio. Bore and end gap checks are also included. This preparation requires an additional 2 to 10 days depending on our availability. It requires tooling and approximately 2 hours of work on the cylinder. The price reflects this.
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