Scooterotica

just rebuild a lambretta 150 gp, first scooter. looking for more power and thinking of buying a 185 kit which is suitable for my engine, will i run into any other problems or will it be a straight swap. At the moment scooter is losing power when in fourth have replaced the jet in carb and removed air filter has anybody got any advice ...

There are issues with GP150 as the gearbox (the same box as the SX150) has a very large gap between 3rd and 4th. if you try any tuning that results in a loss of torque, you can find yourself constantly swapping between 3rd and 4th. However, your principle problem is that the standard 150 doesn't produce much power.

A 175 or 185 (62mm or 64mm piston) conversion will help. the 175 is perhaps easier (and cheaper) as it can be achieved using a conversion piston (straight swap) without changing the con-rod for a longer item or machining the barrel. The 22mm carb and 42mm exhaust will work well. If you want to spend more money, try the Mugello, 24/26mm carb and an expansion pipe.

Even with this extra power, you may find that you are hampered by the ruddy gearbox.

....or a GT186 which is a torquey kit and whilst the gap is a pain, it copes with this adequately with a 16x46 set-up

FOR INFO:

Scootopia/Casa Lambretta UK have a Casa 185 kit fitted to an SX150 demonstrator with SH1/20 carb(118 main..48 idle) and 17X46 sprockets. I tested it a couple of weeks ago and it pulls like a train, easily pulling away in 1st or 2nd and bridges that 3rd/4th gear

Or an SR185 Barrel, with suzi piston and crank 115 conversion LURVLY

soulsurfer wrote:....or a GT186 which is a torquey kit and whilst the gap is a pain, it copes with this adequately with a 16x46 set-up

my thoughts too