Anyone seen an XR50 ?

[Richard Negus]

Kart engine, that is.\rWater-cooled 294cc rotary, based on the Norton / Mid-West single rotor & built in Germany by Paul Woelfle and allegedly the dogs. See www.nova-racing.com .\rFrom photos, it appears to have a full-throttle by-pass of rotor cooling air, controlled by the sort of vacuum advance/retard found on old car distributors.\rMy guess is that at low speeds, a valve in the peripheral port induction is closed and it operates as a charge-cooled engine with a side port in the left plate. At/near full throttle, the valve opens and admits ambient fuel/air directly into the housing through the peripheral port ; there may be no or little rotor cooling air flow whilst this is happening.\rThese karts race on very short circuits where momentary loss of rotor cooling would probably not be a problem.\rAnyone brave enough to try it on their RWYB bike as an alternate to the ejector exhaust?\rR.

[Derek Nicol]

Anyone brave enough to try it on their RWYB bike as an alternate to the ejector exhaust?R.

\r\rErrr... NO! :)

[Richard Negus]

I finally got the chance to examine one by a kart racer. It is much as I expected, with a vacuum-controlled secondary butterfly at the rotor housing port which opens after about half-throttle.\rNot much good for my bike though - the owner says there is a ten second (yes 10 !) limit on use at full throttle and a fifty hour life between overhauls. There don't appear to be any parts the same as my Norton.

[Richard Negus]

I went to a kart race meeting near Grantham ten days ago just to see these engines racing. Although all the engines are sealed by the UK distributor and allegedly all the same spec, some seem to accelerate better out of corners than others.Max engine speed is either 10,400 with cast iron apex seals or 10,800 with ceramic. Engine life is said to be 300 hours (which is more than a season's racing) but the weak point is the centrifugal clutch which burns out if harsh acceleration is used out of the paddock (races are rolling starts). Silencing is quite severe, but they still have the 'prap, prap, prap' sound making them stand out from the industrial Honda power units of the other twin-engined karts.I believe that the FIA/RAC do not recognise rotary engines for karts so they don't race at the more well-known circuits and there seemed a lack of younger drivers.R.ps I've added a few pictures in the gallery.

[andygbsmith]

Hi is this anything to do with Nova transmissions? Andy

[Richard Negus]

quote="andygbsmith"Hi is this anything to do with Nova transmissions? AndyNova Racing is a German company set up to develop the single rotor engine for kart racing. It is similar to the Norton/Mid-West/Diamond engine and some minor parts are interchangeable. However, all the main components are unique to this engine.I believe Nova Transmissions are not associated with the kart engine ; don't they advertise in Classic Racer ?R.