Tuning work - MB Lui 50, Race Reed engine

LUI 50 RACE TUNING?

What fool would Race Tune a Lambretta Lui 50 and get it onto the podium!

Yes this fool did!

This is the second Lui 50cc tune for our good old customer Mark Byron from Oxford Road Runners. Mark and his team does 5 hour non stop off road endurance races with motorbikes for charity twice a year. The first tune was a reasonably mild one just to see how it worked. It worked – they finished both races and had such a good time they wanted more for this year.

Having experienced tuning that engine I knew the ports were tiny, the bore was only 38mm, to make the bike faster – it needed bigger ports! To get bigger ports the ports would have found thin air! So knowing this Mark supplied a cylinder cut up in four pieces to find the weak areas and the thick areas and work around what we had.

As usual time was ticking, he sent his engine last minute, I was booked solid with work. Then I got a message ‘Have you started yet? The race is in 3 weeks, the engines got to be rebuilt, the new 4 speed and clutch needs looking at plus making sprockets and ignitions’! Set up the bigger carb and find an exhaust that works!

Nothing like last minute – I had to drop everything. It needed a rebore and hone to the 40mm Yamaha FSIE NOS piston. Then I had to bolt it on the engine that was mainly seize up with all the mud from last years race to set up the port timings. I had to made and tune a packer so timings were about right – without breaking through the casting. The head needed hand filing to suit, as there was no meat to machine it. The cylinder needed machining on the top to suit the lifted cylinder. And then there was………… the tuning and making that bloody great big one off reed block from our own MB Shorty Reed block …………. I’ve forgot how long it took but know it was one expensive tune!

With the bike thrown together it was dynoed the day before the race!

The message was……………. ‘It F@@king flies’!

A standard Lui did 1.8 brake horse power – this did over 6 brake horse power! No bad at all.

Here’s what Mark told me after the race………..

‘We came joint 3rd over all in our class which was the 2 stroke geared class which was the top/quickest class with all the proper moto-x 50s! Derbi Senda, Aprilla sx50, Yamaha DT etc!!! We had no problems at all with the engine – 5 hours of thrashing it around a motocross track against the others – so it was proper racing neck and neck at times – not only did it come joint 3rd it beat the two Vespa teams as well. A broken throttle cable in the last half hour caused us to miss out off third place by 15 seconds!! And it was down to reliability! We didn’t stop all day. The Vespas both had exhausts coming loose a few times, air filters getting shitty, plug changes (both started missing) The Lambretta Lui was Team Fat Boy the Vespa teams were 2 Men And a Little Lady and the Wrong Un’s Tbh they both had riders in there teams who were better than us and the bikes were all pretty close – although we did have the drop on them out of the corners and thru the heavy mud sections’.

Again it shows the versatility of MrBees 2 stroke tuning.