This right here is a 33hp RB252 Lambretta fitted with a Clubman exhaust, which pulls 4.4 gearing, cruises at 20mph in 5th gear at just 1800rpm, and can be rolled on in the same gear to hit just under 90mph when you stretch its legs. If you don’t quite comprehend what this engine is achieving, it can be very easy to overlook it. But once you start to look at the numbers, and then actually ride the thing… the story starts to unravel.
I’ll cut to the chase and go straight in with the numbers... this test ride took place on an RB252 engine, running a filtered 39mm Dellorto (that isn’t the recommended carb/size – that’s just what this owner had available)a 5-speed gearbox with 4.4 final drive, and is fitted with a clubman box pipe. It kicks out circa 33hp and 26ft-lbs but the most astonishing thing is the fact that you can ride this scooter in 5th gear at 20mph (1800rpm) and then roll on the throttle and take it up to an easy 80mph, and beyond that, if you don’t run out of road! So the scooter has a 60-70mph speed range in just one gear! Of course, you can go to the other end of the spectrum with it and just launch the thing through every gear, and believe me… it pulls! But not in the usual way often associated with tuned scooters where there is a rather underwhelming first few thousand RPM, before the thing launches like a scalded cat and rips your arms off. No, this is a torque driven power delivery and from only 3000rpm it already has 15ft-lbs, 4000rpm is 20ftlbs, and it peaks at 6000rpm with 26ft-lb. The bhp peak is at 7000rpm, but will rev-on to 8000rpm. This combination of torque and bhp, balanced in that way, is what contributes to it being possibly the smoothest and most flexible/user-friendly engine I have ever ridden (as far as classic air-cooled 2-strokes go). Oh, and did I mention that it can also return up to 60mpg if ridden sensibly?
The full report and graph will be printed in September Scootering, where we will examine the details behind it all. But for now, just take a look at the test ride video, where I exercise restraint and pootle along at 20mph in 5th gear, before cutting loose and launching through all the gears to stretch its legs.
It’s also worth noting, that with a JL-TT race pipe on, this is a 41+hp engine… but would then completely lack this type of power delivery under 5250rpm and could not return 60mpg either! Oh, and in case you were wondering, there is no crankcase porting on this engine either! The clubman pipe, and the designer's understanding of it, is what makes the biggest difference to power delivery on this machine. The exhaust is currently exclusive to Darrell Taylor, and is being reserved for the engine build packages which he completes for his customer base, and is therefore not available separately at this time. Be sure not to miss the full feature in the magazine.
Fancy a 265cc TType engine?
Well, Darrell has decided that his premier engine package (to date) will be his 265cc engine running a 72mm bore x 65mm stroke (with no crankcase porting) and will be available in both a high BHP road/race trim (43hp & 28ft-lbs) with an expansion chamber, and flexible touring mode like the scooter above (36hp & 26ft-lbs) with a Clubman. Customers can elect to have either engine characteristic at any time by simply swapping the pipe and gearing. Unbelievable Jeff! See the full story in September Scootering Magazine, get your subscription here: https://www.classicmagazines.co.uk/promotion/sco200