Those of you who read (and watched) our feature on AF Rayspeed’s new products last year will be pleased to hear that some of the new Lambretta parts will arrive shortly.
Small or large block?
The first of those products is the bolt-on reed valve manifolds we showed you in the video above. Ben talked us through his prototype last year and explained why they’re a good option for people running standard and stage 4 cylinders.
These reed blocks are a collaboration between UNI and AF. Designed in a similar fashion to the old LTH reed blocks (no longer available) but done in AF Rayspeed’s own way. They also have a separate small block and large block version, rather than having to modify for each model (LTH just had one casting).
When and where?
The first batch will arrive at AF Rayspeed in mid-April. There will be just 50 units in that first shipment, and I imagine they will sell out very, very quickly.
They will be available from AF, but there will be no pre-orders, and they won’t be on the AF website until Ben physically has them in his hand.
Please be patient, but tell them where you read about them when you place your order.
Why I might add a reed valve to my engine
The Lambretta uses its piston to control the time the inlet port remains open. This means the inlet is open for the same number of degrees of crank rotation, regardless of engine speed, throttle position, or load. That forces an inlet duration compromise that is built into the engine. Too long, and the engine will spit back a lot of fuel at low rpm, too short and the high rpm performance is stunted.
Running a reed valve can allow the inlet to be controlled by pressure. This means that the engine can draw new mixture whenever the pressure in the crankcase is lower than the atmosphere. The inlet is now controlled by demand, rather than forced symmetrical timing.
Pros
- Improves fuel economy and lower rpm performance compared to a non-reed inlet
- With appropriate modifications, the engine can also have a wider usable rev range and run a higher state of tune without losing the ease of use
Cons
- May reduce high rpm – modifications to the piston skirt (and extra porting) will get the power back
What do they fit?
- The Small Block UNI Reed will fit 125/150/175 inlet stud spacing
- The Large Block UNI Reed will fit 200 cc inlet stud spacing.
Easy fitment?
In most cases, it’s a straightforward replacement for the standard inlet manifold, requiring only cutting the cylinder head cowl to fit (some cylinders will need a small amount of fin cutting as well).
Options
Compatible with standard and performance carburettors. Using the aluminium flange, they fit with an SH bodied carb (22/26mm Jetex) breathing through the air box. Using a flange-inlet rubber, they will also fit the PHBH-bodied Dellorto (26/28/30mm) Carburettor.
They can be used with any Minarelli/Yamaha horizontal reed valve, ranging from cheap and cheerful to high performance.
Road testing
I’ll be trying one of these out on my Stage 4 Series 1 in the next few weeks and will report back when I’ve done some miles on it to Austria, if not before.
Iggy
