SUPER HEAD+R Big Bore Kit 138cc
Cylinder Material: Ceramic plating
Displacement: 138cc
Bore Diameter: 59mm
Compression ratio: 13.0:1
Included Camshaft: S-20D
Intake Valve Diameter :30mm
Exhaust Valve Diameter: 24.5mm
Valve Stem Shaft Diameter: 4.5mm for both IN and EX
[Set components]
Super Head + R Head Kit
・Cylinder Kit
・Camshaft
*When the 138cc bore up kit is installed, it cannot be registered as a second class moped.The carburetor and muffler need to be changed.
*There may be changes in product specifications due to manufacturer's reasons.
The legendary cylinder head "Superhead +R" which adopted the know-how of Takekawa's traditional Superhead and OHC's highest class large diameter valves, and demonstrated high power performance.
Super head + R head kit, cylinder kit and camshaft are included in this set.
Super head +R
The standard cylinder head incorporates the technology and internal structure of the original super head to enable the largest OHC valves and the appropriate valve pinching angle, resulting in high output characteristics and stable output characteristics in the high rpm range.
[valve features]
The weight of the larger diameter valve is reduced by the use of a narrower valve stem shaft and waist processing to reduce weight loss.
[valve springs]
Double spring with inner spring and outer spring (unequal pitch)
[Valve spring retainer (steel is standard equipment)
Optional parts are "Special Valve Spring Retainer" and "Tappet Adjusting Nut (Titanium Alloy)".
By changing the retainer to titanium alloy and reducing the weight, the weight of the dynamic valve system is reduced and the tracking performance at high rpm is improved.
[optional parts]
Special valve spring retainer (titanium alloy) (2 pcs) 01-12-084
Titanium Alloy Tappet Adjusting Nut (2 pcs) 00-01-0172
Adopted roller rocker arm
Forged aluminum rocker arms with integrated roller bearings.
In contrast to the conventional slipper type rocker arm, the slipper part is made into a roller bearing to reduce friction loss and follow the cam profile smoothly from low to high speed rotation.
The weight increase due to the use of roller bearings has been overcome by making the rocker arm body of forged aluminum.
Auto decompression camshaft (attached camshaft:S-20D)
An oil line is installed in the center of the camshaft to guide the oil to the cam sprocket.
This increases the durability and lubrication of the cam chain.
In addition, an oil jet passage is installed in the camshaft cam surface, and oil is sprayed from the cam surface to the rocker arm to effectively cool and lubricate.
The camshaft journals are supported by ball bearings on both ends to reduce frictional resistance to the camshaft during starting and at low speeds.
[auto decompression function]
The engine can be started with a light kick force even for vehicles with large displacement engines.
There are 4 types of camshafts with different cam profiles, which can be replaced according to the application.
Cylinder / Piston
The cylinder is made of ceramic plated cylinder which has excellent airtightness, durability and heat radiation.
SP Mukawa's bore up cylinder can be equipped with a stick temperature sensor, so you can measure the cylinder temperature by purchasing a thermometer separately.
[Piston]
The combustion chamber shape and compression ratio are balanced to achieve high combustion efficiency and low weight piston shape.
It maximizes the performance of Superhead+R.
The piston skirt is coated with molybdenum for better initial adhesion.
