Happy 10th anniversary bgm PRO RT Lambretta cylinder kits

(Probably) the best Lambretta Touring kit around

Crazy how time flies by! Ten years ago in 2013, we were able to send out the first mass produced MBgm RaceTour cylinder kits for our beloved Lambretta scooters.

The project started early 2012 as a joint venture between MB Developments and Scooter Center. Mark Broadhurst had designed the kits and produced for some time in the UK. The production in England was time consuming for Mark as it involved many steps to see the finished kit and that made it very expensive.

The main differences between the UK MB version and the bgm versions are*:

Die cast cylinders
CNC machined
Ceramic plated
CNC cylinder head with more cooling
Standardised port timings

*According to Mark Broadhurst’s excellent mbtechsite.co.uk

Over some beers, Mark and we decided to have the RT 195 and 225 kits produced in larger quantities and with a dedicated cylinder head. To cut a long story short the RaceTour kits are considered by many as the best Lambretta Touring kit ever. It is a bulletproof design that gives an ultra-reliable engine with excellent fuel-consumption. Therefore, it is not without a reason that even those with much powerful scooters take out their RT kitted bikes for Touring or Rallying.

TESTING THE PROTOTYPES AND IMPROVING THE SETUP

Here at SC we had eight pre-production kits for testing, four 65 mm and four 70 mm ones. That went on different machines on the dyno and afterwards for proper road testing. There were slightly differences in the setup and we tested many head designs with different compression ratios all machined by hand from Mark. What amazed us at the samples we had and later on in production is the consistency of our cylinder manufacturer. Over the years we have attended so many customer with hints how to set it up and our packer / spacer ideas always worked out and gave the desired squish clearance

FIRST RT 195 AND 225 MBgm RT SAMPLES

Here you see the Excel sheet with some engine info:

DYNO WORK FROM 2011 AND 2012

Here are some dyno sheets done during the development and testing period.

TOOLING AND INNER CORES

However, it did not went without any problems. Mark as a perfectionist was not totally happy with the tooling; it was simply shipped around the world. Mark than spent 30 hours in modifying the port layout of the inlet, transfers and exhaust port. Job done and ready to go on.

CNC MACHINED HEADS MADE IN GERMANY

When the perfect compression ratio for good power spread and the build-in reliability of the RT kits was defined, the time had come to get specific cylinder heads made. The first attempt with casted blanks from India failed badly because of the porosity they were not able to get of the casted item. So a masterplan was needed and we looked into CNC machining of the head. The CNC machine shop across the road of us came into the game and was the solution.

PROPER PACKING RT Lambretta cylinder

The last point was the packing of the kits. It should be safe and also nice and tidy. Easy goal to achieve.

The first proper production kits went funnily out to good friends of us Andy Gillard of (meanwhile) ScooterNova fame and Markus Wessner from Jockey’s Boxentstop fame. The history proof in our computer system looks like this:

RT225 Lambretta cylinder

RT195 Lambretta cylinder

Who –back then- would ever have thought that eight years later Sticky would come up with THE COMPLETE SPANNER’S LAMBRETTA Kit Book, where he has reviewed and dyno tested all the available Lambretta tuning kits and complete engines.

Here are some quotes from Sticky’s Lambretta Kit Book about the MBgm kits:

To be honest the RT kits in the beginning had weak spot. Initially they came equipped with a forged piston that caused some problems with the ring pegs. On 12^th of June 2016, a Facebook group named Lambretta BGM RT195 Problems appeared.

The ring peg problem that occurred on some, but not all forged pistons caused many head scratching in England and Germany. The solution was to change the supplier for the pistons. With the Italian company Meteor, we have the perfect source for literally indestructible pistons.

End of January 2017 we had finally been supplied by Meteor with our new pistons, started a recall on the old ones, and swopped the old ones against new ones free of charge. An offer that was valid until the end of 2017 and since our Italian friends supplied the pistons we had not seen a single piston failing again.

Neil who started the problem Facebook group re-named the group into Lambretta bgm RT195/225 User Group. By far the best and most vivid group for all technical questions relating to the bgm RT kits. At least the questions that our fitting instructions for the RT kits and the extended carb jetting leave unanswered.

We say HAPPY BIRTHDAY RT kit and looking forward for lots of more smiles per miles!