lambretta engine

[bimo]

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 ...

[Knowledge]

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.

[soulsurfer]

....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

[rog60]

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

[Supereibar]

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

[cezeta]

....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