Here it is finally available after nearly a year of development, the RRD Competition 42mm long stroke crankshaft for YAMAHA CHAPPY LB 50, 1F1, 13F ... and LB80. Designed to get the maximum performance and hold the highest speeds.
This very high quality crankshaft has been fully studied, designed and tested in our workshops. It is made of high-end materials in Europe. This crankshaft offers many advantages:
- Machined connecting rod increased + 1mm or 85mm against 84mm of origin, to reduce the forcing and free the motor movement with the large diameter kits!
- Stroke increased to 42mm instead of 39.7mm, which offers an increase in displacement , for example, a 46mm diameter kit like the POLINI which gives 66cc on the original race, will offer real 70cc in combination with this race, the race also makes it possible to approach again the square race (46X42) and to have a better engine behavior.
-Ultra light and ultra reinforced mass with specific crankshaft balancing for the average piston weights of large kits, calculated on a POLINI average ...
- Ultra reinforced machined connecting rod placed on a 16mm diameter crank pin, ultra reinforced foot and head cage, improved foot and head lubrication.
-The ignition thread is a standard "right hand"
-It is not necessary to modify the original crankcase and to mill to fit the crankshaft !!!
* Mounts without machining on original YAMAHA CHAPPY LB50 housings!
** On LB 80, the original stroke is already 42mm, this crankshaft therefore provides an elongation of the connecting rod + 1mm, which reduces the connecting rod / piston forcing. It will therefore be necessary to accompany this crankshaft with a setting of + 1mm on the LB80s. The race will not be changed.
- The price has been lowered for small, limited quantities, with a very high quality of materials and workmanship! It is a very complicated crankshaft manufactured and very specific, this is why we are the first to release a crankshaft adaptable to YAMAHA CHAPPY LB50! Until then, there was only the ORIGIN YAMAHA crankshaft!
The increase of stroke of 2.3mm of stroke and 1mm of connecting rod, will require you to use a base shim of about 2mm), we sell the 2mm shims with a form of base type origin. Then, play with your base gaskets to obtain the desired compression ratio (also to be defined according to your diagrams).
The PMB piston goes down an additional 1.15mm, ideally you will align your lights to the PMB. Be careful, do not use this crankshaft with a kit already prepared with very large diagrams on a normal stroke, the diagrams would end up much too high ... We recommend at most, diagrams of 193/130 if you have enough to exploit them. Diagrams of 188 ° / 128 ° will suit as many people as possible, very efficient and easier to use.
Technical data:
Clutch arm length: 139mm
arm length dimension ignition: 82mm
Crank pin: 18mm
connecting rod: 85mm
Silk left and right bearing: 20mm
Piston needle cage: 12x16x14
Ø mass: 75.6mm
Compression Ratio : Once you have aligned your cylinder to the PMB and with proper diagrams ... Machine your cylinder head so that you have a nice compression ratio. On an air motor, we recommend a 1.00mm squish with a compression ratio of 12 to 12.6: 1 MAXIMUM.
-Mounted on CHAPPY LB50 (stroke increased by 2.3mm, connecting rod increased by 1mm, to be installed with a 2mm shim, compression ratio and lights to be reviewed accordingly.
-Mounted on CHAPPY LB80 (non-increased stroke, connecting rod increased by 1mm, to be installed with a 1mm shim (or seal), no need to modify the compression ratio and the lights.
