Translation
Bidalot recently introduced a new line of performance top ends including the RF70WR which works with the stock crank dimensions of a 40mm stroke with a 90mm rod. The RF70WR is available for the Derbi Euro2, Euro3, and the AM6 engines. This is the Euro2 version of the kit.
Overall the quality of the RF70WR looks to be incredibly high. There is noticeably a little clean up work that needs to be taken into account, but for the most part the attention to detail is quite impressive. The piston doesn’t come stamped with an arrow indicating the installation direction, and this must be determined by the wrist pin clip access recess which is to be place towards the intake.
The exhaust port employs a four bolt exhaust flange mechanism which is comparable with two bolt variants. Bidalot makes the flanges available in three sizes: Ø28m, Ø30mm, and Ø32mm. The cylinder’s design includes a massive amount of cooling to the exhaust port. Bidalot must have discovered an advantage by cooling the exhaust gases to this degree.
The transfers are fairly large for the sized cylinder, especially the rear transfer which feeds into three C ports at the rear of the cylinder. While this will work with unmachined cases it would be best to case match the carters to take full advantaged of these larger transfers.
While the head isn’t modular it does feature significant cooling, and the casting must be a major contributor to the expense of the kit—it is quite complicated in design. In addition to the four traditional engine studs to secure the head Bidalot chose to add an additional four more bolts to ensure a proper seal.
It is exciting to see this level of kit made available for the Euro2 engine. There are similar kits such as the 2Fast for the Euro3 kits, but those have not been made available for the older Euro2 Derbi engine. This makes the Bidalot RF70WR a unique opportunity for folks still running the earlier engine from Derbi.
Bidalot’s website has a fair amount of information for the RF70WR top end. Here is the Google manglization of the French text:
They also provide a PDF file of the installation guide that come with the kit.Here is our latest high engine RF70WR, DERBI 5EBS50 E2.
This high engine is adapted to be mounted with a stroke crankshaft and connecting rod length identical to the origin. However, because of its high performance, we recommend the installation of our crankshaft Racing Factory. Fully modeled in 3D CAD, cylinder sees its water chamber to tour all nuclear transfer and exhaust, with constant thickness, to guarantee high dimensional stability of the cylinder due to optimized cooling.
The cylinder head, heat treated, is also equipped with a water chamber surrounding the combustion chamber, for a good heat dissipation and good cooling. It is self-centered in the cylinder, and returns to 2.4mm in the bore of this release. Fixing the specific exhaust flange, is provided with 4 screws. However, it is possible to mount a mounting flange 2 holes, 48mm spacing.
You will find, sold as accessories, exhaust flanges of different dimensions, allowing the adaptation of practically all the pots market. These flanges are broken down in the following sizes:
Ø28mm x L30mm
Ø30mm x L30mm
Ø32mm x L30mm
Technically, this cylinder unit is composed of:
High engine RF70WR adaptable DERBI E2:
Aluminum cylinder with thermal treatment, coating nikasil Ø47.6mm
Cylinder Aluminum, with heat treatment, self-centered and returning from 2.4mm in the cylinder, high combustion chamber compression
Piston RF50WR hypersilicié Ø47.6mm
7 transfers
Escapement Boosters
New Profile 2018, elliptical, specifically, to reduce the operating clearances
25mm frame size
Chrome steel segment Ø47.6x1, lapped curved, Japanese-made
Axis Piston Ø12x39mm
of base plate gasket set of different thicknesses
Game yoke O-rings
various screws
These promotional photos illustrate the transfers and coolant paths of the RF70WR.
Factory photos of the RF70WR.
