The Moto-Guzzi Nuovo Falcone VOC

I got the idea of the squash balls from some spring assisters sold to people who tow caravans.
I was suffering from Iron Butt: during a long ride I found I was slipping to the rear of the saddle and feeling the effects of the seam and piping at ehe back pressing on my coccyx. So I went looking for some method for stiffening the saddle springs to they would let the seat tip backwards quite so much.
Once I'd wrestled the squash balls in between the spring coils I had no further problems.

"Although that Amazon one does mention metering, it seems to be on or off with the toggle?
Or maybe the needle is adjustable? It's certainly cheap enough!"

The central pillar has a pointed end that fits into the outlet at the bottom of the reservoir. It is threaded and can be screwed up and down to adjust the flow rate. The sping toggle at the top lifts the needle to allow the metered flow, or drops the needle to stop the flow.
It's simply a case of remembering to lift the toggle before you ride off, and dropping it again when you park.

Nope - reverse flow.
It's possible for pressure pulses to go back up the inlet towards the carb. If they reach the carb they go through, pick up some more petrol, then come back on the next intake and pick up yet more petrol.
This is one reason why lengthy valve timings (valves open for a long time) can lead to poor slow-speed running.

Anti-reversion cones and similar measures are a way to stop the pulses travelling back up the manifold - they also work for exhausts.
Or you could go the Japanese route and use several small valves with shorter timing and more rapid opening and closing controlled by an overhead camshaft. But where's the fun in that?

This was my attempt to make my own, cheap, version of a Scottoiler.

It was based on a drip-feed oiler. You can see these on old steam and traction engines (appropriate) and some machine tools. It is a glass or plastic vertical cylinder that acts as an oil reservoir with a central spindle that controls the leakage rate out through the bottom of the reservoir.
I bought mine from Axminster Power Tools, but I'm not sure if they still sell them. Amazon does, oddly - see http://www.amazon.co.uk/100ml-Spring-Toggle-Needle-Valve/dp/B00KHSVTFA/ref=sr_1_3?s=diy&ie=UTF8&qid=1416497926&sr=1-3&keywords=Gravity+Drip+Feed+Oiler

I drilled the back of the left side toolbox and fitted a spring clip under the seat and next to the battery. This clamps around the body of the oiler and the ends of the clip are retained by a zip tie (all praise the mighty zip tie).


And in case you are wondering what the black objects are inside the seat springs, they are squash (the game) balls. This is a really easy way to boost the springs a bit and stop the seat from sagging, especially if you are a big lad and like the pies.

The oil feed is led down behind the toolbox and into the dry flywheel cover, to deliver oil directly to the gearbox sprocket. This means that any excess is less likely to be flung onto the rear tyre.


After adjusting the flow rate I used chain-saw chain oil (cheaper than motorcycle chain oil and available from farming supplies places) to lube the chain.

(as in suck, squeeze, bang, blow)

Prior to selling the NF I had been toying with the idea of replacing the carburettor. Not for fashion reasons, but to improve the inlet shape as part of the grand plan to improve the old nail.
The engine uses two shapes of inlet manifold, depending on the source of the bike. The civilian ones seemed to have a rearward-facing (downdraft) manifold and the military ones had a sideways-facing (sidedraft) manifold. Neither of these is really conducive to good gas flow.

I played with some designs to try and make a downdraft manifold, but the frame, front wheel etc get in the way, and we do need the front wheel. (Only Ogri can get home with a flat front tyre by wheelying the whole way back)

One option I was considering was a downdraft carb. There isn't much room under the tank but the Citroen 2CV has a very nice twin-barrel carb that might do the job. Fit the top of it with a low-profile bellmouth and an airbox leading out to the original airfilter position, and it might just work.
The 2CV carb's barrels are timed to open in phase, one after the other. This means that I could orient the carb so that the barrel that opened first at small throttle openings was at the top side of the inlet port. This would make the closed barrel (potentially) provide a bit of anti-reversion in the slow-moving side of the gas flow.
The complication is that I have no idea how to change the jets in one of these carbs, or even if alternative jets are available.

Plan B was to use an SU carb, modified according to the wizdom of Mr Vizzard (author of 'tuning BL's A series engine' - the bible of how to improve bad engine designs). This would hang out in the standard position. Using a CV-type carb allows the use of a much larger choke size without the complications of the engine drowning if one opens the throttle too quickly.
The challenge would be the inlet manifold.
What I had in mind for this was to put the carb as far forward as it would go and clear the frame tube, and the manifold back to provide as much downdraft as possible, then bring the manifold to a slightly smaller diameter than the inlet port in the head. The 'mismatch' would be at the lower (with respect to the head) side of the port, with the end of the manifold finishing with a sharp lip.
The aim of this was to provide some anti-reversion - the valve timings of the NF engine are fairly long, to allow the huge and heavy valves to be moved back and forth. So the idea was to deter any tendency to reverse flow back up the inlet at low throttle openings.

I never did get around to it, although I do have the SU carb lurking in the garage awaiting the attentions of a Dremel.

Anyone fancy getting their hands on a 2CV carb and having a go?

I think this is a diagam of the 2CV carb - the jets do look like changeable items.

The plug position has a big effect on the burn time of combustion.
The standard head has the plug offset to one side to clear the valves. This means the burn starts at one side and has to cross the head volume. This is one reason why the maximum advance is so large - to give the mixture time to burn.
Raising the compresion ratio reduces the space in the head and means that the burn will complete more quickly. However, if this can only be done by raising the dome of the piston to fill the hemispherical head, the burn will be compromised because it has to find its way across a thin space with large amounts of wall drawing heat away.
Look at a modern 4-valve head - the valves are small and each pair is set parallel with a narrow angle between the exhaust and inlet set. The plug is central. The piston crown is wedge shaped to fill the head space but confine the burn volume to the space around the plug. The maximum advance is a lot less than for the New Falcon.
(And for comparison, take a look at the 2-valve head used in the Honda Jazz 1.4 engine. This has two plugs, as again the use of two valves prevents the plug being placed in the centre of the head. Honda also time the ignition to the two plugs separately so that the engine burns better at low throttle. Clever.)

This modified head design has three benefits: it reduces the head volume and provides some squish, and it starts the burn at both sides using two plugs.
The increased compression ratio helps reduce burn time and gets more torque out.
The (modest) squish helps reduce burn time.
Having two plugs decreases burn time.
Plus the combustion space has a better shape, being more compact.

The net efffect is that the engine should produce more torque (=more power), need less ignition advance and (thrashing excepted) be more economical.
What's not to like?

:-)

Compression ratio....

So, the original engine is 6.85:1
If we assume that the additional welding added 15cc of metal, that would make the new CR around 8.1:1

The amount of weld added is a guess - here are the numbers for various amounts:

Weld  CR:1
5cc     7.2
10cc   7.6
15cc   8.1
20cc   8.6


Ooh, and an important point - the second spark plug is a 10mm. There isn't much room for anything bigger.