Overhauling of engine, altering inlet, ignition timing

Pictures by Tonni
Dutch to English translation by FonS

Ofcourse we start by removing the engine from the frame, no further explanation needed.

Remove the flywheelcover, so you have access to the flywheel. Remove it with a flywheel-puller. If you don’t have one, you can press the rubber from the coil-wire inside the crankcase, put a screwdriver through the hole and gently tap against the inside of the flywheel. But always tap, turn it a bit, tap again and so on.

Now you remove the ignition.

The next step is removing the cylinder and head.
No explanation needed.

Secure the engine in a vice (put some cloth between it to prevent damaging).

Use a gas burner to heat up the right half of the crankcase. If you don’t have one you can use a paint stripper or you’re mothers cooking-stove.

Remove the right half of the crankcase and repeat the procedure for the left half of the crankcase. Try not to heat up the crankshaft as well, and if you don’t want to overhaul, be careful not to burn the seal.

If everything went well, you now have two halfs of the crankcase and the crankshaft with the bearings on it (they stay in de crankcase as well sometimes).

The following bit is for people who have a column-type drilling machine and want to make the inlet 13mm.

Put a well fitting pipe clamp around the inlet (to prevent tearing while you�re drilling).

The column-type drilling machine with 13mm drill.

It’s best to remove the stay-bolts from the crankcase, so you can put it upright for drilling.
Measured from the end of the inlet pipe, you can only drill up to 18mm deep. If you drill any deeper, it might cause a hole in the crankcase.

This is how it looks after drilling.

Now it’s time to file the inlet. Always file up and down, never left to right! How far up and down you go, depends on your setup (cylinder and so on) or just how far you want to go. You can file to the edges of the inlet area (stay 2-3mm away from the edge, to prevent leaking).

When the filing is done, you smoothen the surface (you can use a grinding tool, but always work carefully, the material is quite thin).

When everything is done en smoothly finished, it should look like this (unfortunately it’s a blurry picture).

Ofcourse, remember to clean the crankcase well!
Now it’s time for the overhaul. First you remove the old bearings from the crankshaft. Secure it in a vice and use two screwdrivers to get underneath the bearing. Then you use them as a lever to remove the bearing. Start with small screwdrivers and then some bigger ones.

Crankcase, -shaft and overhaul kit:

Place the crankshaft in a freezer for a few hours. You could heat the bearings a bit before mounting them (I never do this, cooling the crankshaft is enough). The crankshaft will shrink because it cools down and if you heat up the bearings, they will expand. Now you can easily mount the bearings (don’t forget the SHIM rings!).

The crankshaft is now ready to be mounted:

Heat the large half of the crankcase well.

Put the crankshaft in place and position the gasket as well. You can use two bolts to hold it in place better, like you see in the picture.

Now heat the other half of the case.

When it�s hot enough, it�s easily placed around the bearing.
Remember to let it cool for a bit, you can get burned easily.

Now you can fit the case�s bolts. Tighten them evenly and cross-wise. They don�t need to be extremely tight, it�s only M6.

Check if the gasket is sticking out, if necessary, trim it with a knife.

Now you place the new seal (don’t do this earlier, because you could burn it when you heat the case). Put it as straight as possible on the case and evenly press it down. No deeper then the edge, or it will touch the bearing.

Reassembling the ignition, preferably with a new condenser and breaker points.

The following pictures are for the assembly of the ignition. This it where everything should go.




When everything is back in place, you need to adjust the breaker points. Align the key (wedge) with the little hammer on the breaker points.

Adjust the distance between the points to 0,45mm using a feelergauge. Tighten the screw and check the distance. The gauge should be able to slide through smoothly.

Now it’s back to mounting the cylinder and so on.
One last tip: put the flywheel in place and then mount the clutch to secure the flywheel. This prevents breaking the key (wedge) when you mount the clutch after placing the engine in the frame.

Good luck :thumb

Pictures by Tonni
Dutch to English translation by FonS