PROJECT THUNDERBIRD

1

Fitting one rocker box makes the engine easier to turn for valve timing check. Once you’ve recorded the inlet figures, swap the box to the exhaust valves and check those.

4

Before I fit the left engine plate, I slot the footrest bolt for a screwdriver. It needs loosening for primary cover removal; this saves wedging your fingers onto the hex behind.

7

Before fitting the second box, fit all the bolts/nuts finger-tight and nip the two head bolts up. After that, torque the head bolts and finally tighten the smaller fasteners.

8

As per the rocker gaskets, anneal any copper washers to soften them. Get the flame heat to a bright red, quench in clean water, they will seal like new again.

2

The original was a mess, so we ordered a new alternator stator. Make sure you have about 10 thou clearance all the way round the rotor; any rubbing spells disaster.

5

Back on the bench for rocker box fitting. Copper gaskets work well on Will’s 500 so we’re using them. Anneal (soften) them before use and apply sealer; we’re using Wellseal.

9

To replace his tired original, Will’s fitting a Morgo oil pump. It has a higher output, it’s well made – and it’s also brand new, so it makes a good replacement.

3

We fitted the engine from the left, front high, located the gearbox under the rear fork pivot, then lowered the front in place. A big moment; Will couldn’t resist taking a seat.

6

Turn the engine so both pushrods are level; then, thumbs lifting the adjuster end of the rockers, lower the box until you feel the rockers engage and push downward.

10

Next job was to replace the big-end feed oil seal. You can lever it out with a screwdriver, but protect the cover with an offcut of aluminium beneath.

13

I stick a bulb on a wire inside the tank to reveal any nastiness; a bit of oil pipe pushed onto a paintbrush handle extends it to reach the inner depths.

16

... where its plunger engages with a notch in the crankshaft at TDC. On this 1964 bike, we will use the TDC tool to zero the disc.

17

Disc adapter screws onto the exhaust camshaft, saving further dismantling. The cam spins at half engine speed – 10 cam degrees is 20 at the crank.

11

Carefully clean all oilways before pressing in the new seal. It faces the oil supply – points seal is identical, but faces inward. Ensure circlip is securely fitted.

14

Cleaned and dried, we fitted the tank. Will bought this ‘high-pressure fuel pipe’ – reinforced, British Standard approved and black, I’m happy with it.

12

No pump likes pumping dirty oil around. Will’s using this chromed oil tank, but gunge needs washing out. The battery? No, we’re not using electrolysis...

15

Points ignition is staying; these are the timing tools needed: crankshaft TDC tool and cam-mounted degree disc. TDC tool screws into a crankcase hole...

18

Reverse the engine to the timing position and adjust the piston stop to touch the crown. For future timing, just turn the engine till it hits the stop, and set the points to break at full advance.

19

The Amal Monobloc carb came with seized screws, bits missing and two throttle springs to overcome a sticky slide – unsuccessfully. Can it be saved? We’ll try...

22

In the float chamber two things are missing – the little brass spacer on the spindle that stops the float rubbing the cover – and the float needle!

25

Gripping across the large diameter in a vice, I ‘sprung it’ – bouncing the vice handle a bit at a time while using finger-touch to check how much it moved – success, it now slides freely!

26

With all the missing/broken parts replaced and the rest cleaned up, the carb is ready for Will to reassemble – using a period accessory finned alloy float chamber cap for a bit of patter.

20

If you have to grip the carb in the vice, use aluminium jaws and grip it across flange and inlet as gently as possible; it’s least likely to cause distortion.

23

Pilot jet and air screw were both seized. Use plenty of heat and remember that it’s better to have to scrap the jet than the carb body.

21

All jets and drillings are accessible on the Monobloc, so no need for ultrasonic cleaning, corrosion like this is easily cleaned off with solvent and brushes.

24

Body distortion is the usual cause of a sticky slide, but another slide worked fine. Our original was slightly off round, like it’s been squashed.