If you’ve missed the first two parts of this feature you can catch up on them here. With plenty of videos and a few engine casing problems along the way this series is well worth watching and reading.

In part 3 we finally get the scooter up and running. It took the best part of a week to get to this stage, two engine strips, three engine casings and lots of patience. Pretty much everything that can go wrong did but at least the top end went on without issues.

bgm pro sport big box fitted to lambretta engine
‘Fits like a glove’ is a turn of phrase made for the BGM BigBox Sport, it fits well, doesn’t’ compromise ground clearance and isn’t at all noisy.
Friday We were back at Simply Retro bright and early for our fourth day. It’s surprising just how much time it takes to get all the fiddly bits done on a Lammy build. We also fitted the BGM Clubman Sport Pro exhaust. It was supplied unpainted so I’d sprayed it with heat resistant paint whilst Rob was messing about stripping and building three engines. The exhaust fits perfectly and with an engine on the bench you can see just how close it sits to the casing. I was impressed.
Although the BigBox Sport has an underslung muffler (other than the tailpipe) you still retain the look of a standard box exhaust.
YSN 30mm carburettor
Carb manufacturers should make jets with numbers in braille for ageing two stroke fanatics.
Time to get the engine in then. That all went fairly easily and it was soon cabled up. The rear brake shoes went on, followed by the hub but the wheel wouldn’t turn. The shoes needed dressing a bit and the cam needed a little grinding off it to give enough clearance. Soon sorted though. We were using a YSN 30mm carb and had a rough base setting for the jetting, although we didn’t have the needle we needed unfortunately. Even so the scooter was back in one piece and after three kicks it fired into life. I’m not sure who was more relieved, me or Rob! As expected the scooter was running quite rich but it was rideable. Just the floor runners to go back on and it was time to finally leave Simply Retro in peace.
Diablo Al talks us through the dyno and tells us all about the aerodynamic properties of a “Fat Lass”
Linsey clocked up a few miles in the afternoon then over the weekend we got over 100 running in miles done. The following Tuesday I’d got both my new Pinasco 251 and Linsey’s RT225 booked in at Diablo Moto for a dyno and final setting up.

After Al had worked his magic we ended up with 19.1bhp and 15.3ft-lbs of useful torque. He talks us through the dyno findings and his observations in the video above. As expected the gearing was a little tall but we’ll drop that a bit over winter (we didn’t have the chain we needed to run a 17-tooth front sprocket when we built it so had to compromise).

The dyno above is an all-gear run showing a healthy 19.1 bhp and 15.3ft.lb of torque but the power could be moved lower in the rev range to make long distance riding more pleasurable.
After the dyno

The difference with the scooter set up was immense. It sounds much crisper, performs very well and with the aid of the BGM filter it’ll keep the bodywork much cleaner as well.

The week after the Dyno, Linsey rode the scooter to Southport and back where it performed impeccably. The scooter is still running a standard tank and the range is perfectly adequate, at most fuel stops whilst riding in a group she was getting just less than 4-litres in the tank after around 45-50 miles. The best thing though is that she absolutely loves it and she’s regained confidence in her scooter.

We’ll keep you updated in the future once its had chance to do a few rallies.

Words, photos and video: Iggy

Thanks to Rob at Simply Retro and Al at Diablo Moto

Also thanks to BGM and AF Rayspeed for help with these articles.

bgm rt race tour kit
UK stock available now We currently have both RT195 and RT 225 kits in stock, we also have BGM Clubman and Clubman Sport exhausts in stock. If you’re looking for anything else from BGM/Scooter Center email us at: shop@scooterlab.uk and we’ll order it in for you. Check out BGM in the SLUK Shop here.

Sticky’s kit book

If you’re thinking about some extra power for your Lambretta, or you’re confused with the abundance of modern kits, Sticky’s Complete Spanner’s Lambretta Kit Book really is an invaluable resource.

Packed with info on all the main large and small block kits, the components that work with them, comparative dyno results, real-world owner’s opinions, advice on set up, gearing, build tips, torque settings and a whole load more besides.

If you haven’t got a copy put it on your Christmas list, or buy yourself a copy now.

Available through the SLUK Shop here.

 Buzzwangle

A couple of other products made this build a bit easier, firstly the Buzzwangle. It makes setting up scooter timing much quicker and more precise. You can order yours here. 

SLUK Clips

A pair of SLUK Clips stop that fiddly job of refitting the rear runners and bridge piece so much less bother. Every Lambretta owner needs a set on their scooter. Get yours here.