Cam shaft reassembled using engine assembly grease

I coated all the pieces with engine assembly grease then put everything back together.

Adding the extra O-Ring to the rocker arms

John come up with the idea of placing an o-ring at the base of the rocker arm before you add the paper gasket. This will further protect against leaking.

Valve lapping

Craig at Scooter Works told me I had to 'lap' my valves and explained how it increases compression.

I bought the lapping sticks and the grease and went to work while watching old episodes of Star Trek TNG.
Removing the spring and then replacing them was very quick this time.

I first used the course and then the fine grit. The results look good. The top one below looks good.

A lot of improvement can be seen on the right one. The left one has not been done yet.

Ultrasonic cleaning of the carb

I have my carb cleaned using an ultrasonic washer.

Here are all the pieces:

Here it is back together: 

Some parts in the diagram I do not have (circled in red). Some of these parts are for different models of the carb. 

Font wheel speedometer screw

To replace the front bearings, you have to remove this screw. It is reverse threaded so it must be unscrewed clockwise. There are arrows on it to show the direction to remove.

You need a special tool to remove it. I don't have it yet. I just ordered it. I tried to remove it with other tools and by heating up the housing, but it just doesn't work.  Now I must wait for the delivery.

Drive shaft bearings - removing / replacing

Thanks to Scooter Works (my friend's classic scooter repair shop) in London, I learned the trick to removing and replacing the bearing outer rings.

Because the outer metal casing is cast and the bearings and rings are hardened steel, the outer metal casing heat up quicker than the bearing ring.

Heat up the casing with a torch. When it is hot enough, you can just pull out the ring.

Replacing the rings is even easier. Heat up the housing, freeze the bearing ring, and it will just drop in.

The bearing must be completely greased up before dropping it back in.

Here are the bearings and rings.

Heat up the casing.

Freeze the bearing ring.

They just drop in without any effort.

What gasket goes where?

When you buy a gasket set for an engine, you always get a few pieces which you have no idea where they go.

This first happend with my Austin Healey Sprint. Now with my Nimbus.

Below is the response from Lars:

1: These 8 little o-rings go on the rocker arm shafts before you put on the paper gaskets. This is an invention of John (JC Nimbus) to counter overly generous tolerances    to the cam shaft housing's rocker arm holes. They were not part of the original gasket set. I will be adding these!

2: These strips are used on the outgoing side of the gear box and on the final gear. They are designed to tight up against the prop shaft. They sit inside where the prop shaft enters gear box and final drive.

3: On the new type gearbox (upside down Y-shaped clutch engagement arm), there is a recess where the end pin to the clutch engagement pin exit the gear case lid. It goes there.

4: Petrol tank gasket.

5: Gear-case oil return seal. Sits in the sump where the down going oil return channel meets up.

6: O-ring sits where the kick starter shaft exit the sump.

7: Gear-case oil feed line seal. Sits on the jet from the oil feed line that is routed through the engine that meets the gear case. Make SURE you do not have TWO seals there! If you do, you will crack your gear case housing during mounting!

8: Dynamo neck O-ring. Sits inside the holder with four nuts mounted around the dynamo on the under side of the cam shaft housing.

9: Oil sif (filter) seal. Sits around the strainer towards the back side of the plate that holds it in place in the sump.

10: Vacuum lead seal. The vacuum lead also serves as the oil filler cap and sits on the top side of the crank case, with an angular tube going up to the carburettor and a bell against the crank case. It sits on the underside of this aluminium bell.

11: Grease seal for the disengagement bearing. It sits inside the shaft where the clutch disengagement bearing is with the opening up towards the bearing, pressed all way down in the shaft. The cavity between the seal and the gear case lid should be filled up with grease of type Castrol APS-2. Be generous! This is the only lubricatoin this bearing might get. Observe! If you do not remove the old seal, you can not disengage the clutch since there will not be enough movement for the disengagement bar since the bearing will hit the top seal. I did that myself, and when it was found out that I had TWO seals in there, the guys at John gave me the unflattering name: Two-timing Lars.

Rebuilding the valves and valve springs

The finished product looks very nice. It will clean up even more after I wash it. I can't do that until it is back on the engine and the engine is mounted.

I used masking tape under the valves to keep them from falling down while I compressed the springs and installed them.

I painted the head and the exhaust manifold at my apartment on the balcony. I first degreased it, washed it, and dried it. I then used Panel Wipe to do a final wash. I warmed it up in the oven before painting it. After painting it (on the balcony in a box) I put it back in the oven and baked it for an hour and a half at 200. That dried it well. 

Normally, high temperature paint dries and sets from the heat of the engine as it is running. The oven also works.

Cam housing rebuild

Rebuilding the Cam section is very simple and straight forward. All the pieces go right were you think they go.

I should have have the tap screw and nuts zink plated. I didn't think about it at the time.
I painted the 8 arms black and also the edges of the arm bases since they are visible. I could not zink plate these pieces because they are partly internal to the engine. I didn't want zink bits wearing off and falling into the engine.

A warning when you clean the cam housing... there is a copper oil tube that goes from the base of the housing to the far end. This tube has holes along it. Oil is pumped up and through the tube where it drips down onto the cam. If you have the cam housing vapor blasted or blasted some other way, the holes must be plugged up tight or grit will get into the tube.
I went to Colins Chemical Blacking. They didn't plug the holes so I had to used compressed air to remove the grit.
Next time I will go to I Cleenz Macheenz (http://www.icmhome.org.uk/).

Rebuild begins

I started rebuilding it today. I make good progress. 7 hours.

It took 3 tries to get the steering column (or whatever it is called on a motorcycle) together. One little bump and the bearing would bounce out of place and I would have to start over.

My workshop

My simple workshop.

You can see the nose of my BMW restoration project in the top right corner.

Cream? Yes please

The wheels and other parts have just been painted. I can pick them up tomorrow (Friday).
I can also pick up all the nuts/bolts and other parts from the plating company. Some have been zink coated, other blackened, some just cleaned.

Paint it RED

The red bit were painted today. They looks good.

Tomorrow I hope he starts with the cream parts.

Painting - primer

The painter is busy painting the parts today. I stopped by and it is looking great.

Engine exposed

I removed the sump and turned the engine upside down. It looks very simple.

The oil pump and distribution system is simple.

The bearings are massive.