Below are the available bulk discount rates for each individual item when you purchase a certain amount
● YUMINASHI 3MM OFFSET STROKER PIN Ø26MM X L39MM (MONKEY Z125 / MSX-GROM125 / C125 SUPER CUB / WAVE125i / ETC...) (13381-K0F-300)
● YUMINASHI 3mm Offset Stroker Pin (0.11811 inches), to increase the stroke of your stock crankshaft with 6mm (0.23622 inches).
● The diameter of this offset stroker crankpin is Ø26mm, the length is 39mm.
※ Check before you order if a crankpin with these specification is what you are looking for.
※ The special needle bearing is not included, you can order the SPL needle bearing for this crank with this LINK.
● THE 13381-K0F-300 3MM OFFSET STROKER PIN Ø26MM X L39MM IS THE CORRECT CRANK PIN TO BE INSTALLED ON:
※ The stock crank pin from the Kawasaki models above are stock Ø26mm X L42mm, the offset mid area is 14mm which is the same as the stock needle bearing & connecting rod width.
※ Keep in mind that a longer stroke crankshaft will required an aluminium spacer to be installed underneath your cylinder, and that you will need to use 2 cylinder base gaskets, a longer cam chain and usually 2 extra dowel pins (LINK).
Keep also in mind that depending on the connecting rod length you are using, you will need to install most likely also 4 new, longer cylinder studs.
TUNING TIPS & THINGS TO CONSIDER ABOUT STROKE/CONROD RATIO'S:
● We recommend for a powerful and reliable engine a stroke/connecting rod ratio of 1.75
● This means that if your stroke is 57.9mm, which is the case with a Z125 Monkey, a MSX/GROM125 and C125 Super Cub etc, that you can calculate the recommended connecting rod length like this:
57.9mm x 1.75= 101.33mm for the connecting rod length, or something close to this number such as 100mm.
The stock stroke/conrod ratio of these Honda engines is 1.6 .
If you install this 3mm stroker pin which increases the stroke in total with 6mm, and results in a 63.9mm stroke, then we recommend a connecting rod length of:
63.9 stroke x 1.75= 111.83mm conrod length, or something close to this number such as 110mm.
With 63.9mm stroke and the stock 1.6 ratio you get as result a 102.24mm connecting rod with as benefit a shorter engine, but as downside less torque at higher rpm's with the same engine displacement.
● We recommend the 1.75 ratio over the stock 1.6 ratio because generally, a lower ratio means a high rod angle, creating greater potential for accelerated wear to cylinder walls, piston skirts and rings; the increase in friction can also raise coolant temps.
A low ratio can also lead to higher levels of engine vibration.
A low enough ratio, due to the severity of its rod angle, can drive a piston right into the cylinder wall.
Higher ratio engines, on the other hand, don't have the same friction concerns, but compromise in other areas.
Air does not fill the intake ports with the same velocity, and there is less demand for the ports to flow as well since there is more time to fill and scavenge the cylinder (we discuss this phenomenon later).
A longer rod makes more torque with the same piston force, and since it's less angular than a shorter rod, reduces sidewall loading and decreases friction.
All of this adds up to more power.
Longer rods also give the pistons more "dwell," the brief periods of time the piston is at top dead center and bottom dead center.
A longer dwell allows for better flow of intake and exhaust gases since the piston moves slower between up- and downstrokes.
Longer dwell also offers more time to fill the cylinders during the intake stroke and more time to scavenge during overlap. And since the piston hangs out at or near TDC longer, the combustion stroke has more time to deliver a thorough release of energy on to the piston.
In a stroked motor, the piston ultimately reaches greater speeds to cover the additional stroke. The speed makes intake, compression and exhaust strokes more turbulent and, consequently, more powerful. It also comes with its price in component wear, something to consider when looking into parts that increase stroke.
With a short stroke and a long rod, however, the piston accelerates more gently from TDC. It picks up its greatest speed further down the bore, at the point where the crank pin relative to the rod angle reaches 90 degrees. Since the pistons move from TDC slower, the entire bottom end absorbs less mechanical stress.
● Most engine builders believe longer rods are better, but some enthusiasts still dig the low-rpm torque that shorter rods can make.
We advise builders who want a ratio of less than 1.6:1 to use the strongest aftermarket rods they can find, given the angle.
The 1.6 stroke/conrod ratio is one of the most important reasons why the stock connecting rod of the MSX/GROM125, Z125 Monkey, C125 Super Cub, etc are breaking with a big bore installed.
If you would install a 100mm connecting rod instead of the stock 92.5mm conrod on the stock stroke crankshaft, then you could easily install a 183cc big bore kit, you wouldn't break the conrod and make more power...
We also recommend with a 1.6 ratio or less aftermarket sleeves to better fend off the lateral stress created by the rod angle.
SMART SHOPPER TIP:
※ BUYING MORE THAN 1 PIECE CUT THE TRANSPORT PRICE, AND YOU RECEIVE A 10% DISCOUNT ON TOP OF IT!
All prices are in THB