Project Racer - Monday 13.02.2012/XNUMX/XNUMX


12 days left until the custom show in Ried….

We have now defined cylinder outlet and overflow angles and processed the cylinder accordingly.

The next step is to check the crush dimension, the distance from the piston to the cylinder head.
Polini gives for the Evolution Direkt a recommendation from 1,00mm.
To get an idea of ​​whether and, if so, how much the cylinder needs to be milled, we first measure the piston residue.

Here we come to 1,2mm. Plus the thickness of the cylinder head gasket of 0,5mm, we come to a crush dimension of 1,7mm. So our Polini cylinder has to be 0,7mm shorter.

In order to be able to machine the cylinder, it is prepared for a clamping device.

Here with the jig for processing.

So prepared, it goes to the milling machine - briefly measure it

and then the chips fly ...


Now comes the moment when it turns out that we have measured everything correctly and that the hogger has done a good job.

We use tin solder to determine the new squeeze dimension. As with measuring, it is important that all measurements are taken parallel to the piston pin. Otherwise the piston could tilt due to its play in the cylinder and thus falsify the dimension.


Ah, everything went well - precision landing!

Before we start assembling the engine, there are other little things to do.

For example, the prime mover still needs to be prepared.
The GP-One clutch is mounted with its own so-called rep kit, i.e. the cover disks under which the primary springs do their work as shock absorbers.

So first we have to free the primary from the simple cover disks. This task is done quickly with an angle grinder.

Since in our case the clutch has to be assembled in the engine, we mount the rear cover disc of the clutch on the large primary gear and insert the springs.

We grind the cone of the auxiliary shaft and the clutch basket so that the power that our projectile hopefully develops sufficiently can also be transferred to the gearbox Valve grinding paste each other. This is to prevent the clutch basket from starting to work on the small cone of the auxiliary shaft due to minimal angular errors.

Grinding in is repeated until a uniform contact pattern is obtained on the auxiliary shaft and the basket.
Also the fan wheel cone of the Vespatronic we grind in like that. Especially when it comes to the flywheel mass of the ignition system, it is important that the cones fit together really well. Due to the high speeds compared to the clutch, high-performance motors can otherwise quickly cause vibrations and thus damage.

Now that all the preparatory work relating to the motor has been done, it is now time to insert the ball bearings and assemble the housing.

With a normal cast aluminum motor housing, a hot air blower or a small blowtorch is usually sufficient to heat the housing to approx. 80 ° and allow the cooled bearings to fall into their seats.

However, the CNC housing is so massive that it would be quite time-consuming to bring the housing to the appropriate temperature with a blowtorch.

So we just put the case in the oven.
Unfortunately, this sometimes leads to irritations when preparing for lunch.
But today: engine before potato casserole!

Usually you would use the ball bearings Cooler spray cool quickly so that they fall so shrunken into their seat. But with the current outside temperatures of around -7 °, it is enough to simply put the ball bearings in front of the door.

When installing the Primary bearing 16005, it is noticeable that the seat has some play, as is the case with the Piaggio housings. In order to avoid that the bearing starts to move back and forth in its seat due to the transmitted torque to the gearbox and the actuation of the clutch, we compensate for the play Shims .

With this bearing, it is important that there is no shim washer on the auxiliary shaft side, as the oil collecting plate is mounted here, which in turn supplies the bearing with the essential lubrication.

As long as the ball bearings are still warm through the housing, the crankshaft, main shaft and, as shown above, the primary drive can be used very well.

Shift rocker, Kichstarter segment and shaft seals follow.

Before assembling, we simply glue the paper seal to one half of the housing with grease.

The shaft seal seat of the crankshaft is also given a little grease so that the sealing lip of the shaft seal does not turn inside out and the spring pops out during assembly.

When assembling the housing halves, it is sometimes necessary to move the gearbox so that the gear wheels of the main and auxiliary shafts find each other. Since our disc brake hub is on the way to be galvanized, we simply take the pattern for the main shaft toothing.

As soon as the housing halves have come together and the housing bolts are tightened, the piston and cylinder can be assembled.

Before the piston disappears into its cylinder for a long time, it and the lower connecting rod bearing of the crankshaft get a drop Motul with on the way.

The cylinder only comes with without a base seal Sealant assembled.

After the cylinder has been installed, the cylinder head is then tightened step by step and crosswise with the torque wrench.

That's how far we are today ...

  1. Attila
    Attila sagte:

    Hello Alex I like nice project

    just have a quick question on the crankshaft clutch side I saw a 6204 bearing ?? normal 6303

    which crankshaft did you use?

    have fun with the project

    Hello Attila

    • alex
      alex sagte:

      Hello Attila,
      For the Polini crankshaft with a stroke of 52,8mm, a 6005C3 is used on the Lima side and a 6204C4 on the primary side, as the crankshaft stubs are larger in diameter.

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