12. Suggested specifications

Assembly manual

12. Suggested specifications
Richard Taylor wrote this manual.

All Lambretta engines will appreciate in value eventually even Li125s. One of the objects of the 186 kits is to utilise the least valuable engines and preserve future collectibles such as the 175’s, Li S and SX150 etc.

GT186/200 Touring
1. GP Crank and Electronic ignition
2. 42mm Clubman big bore exhaust
3. New bearings & seals throughout (GP bearing to suit crank)
4. New clutch plates
5. New GT clutch springs
6. Gran Turismo chain tensioner
7. Dellorto PHBL 25 or PHBH30 Carburettor with cable choke conversion, elastic mounting and SS clips
8. GT186 or 200 kit with 25/30mm L/Hmanifold
9. GT Porcupine head
10. Primary drive gearing 17/46 (150 gearbox), 18/47 + 82 link chain (125 gearbox)
11. Casings not matched.

GT186/200 Fast Touring
As Touring but with:
1. Matched casings
2. Full circle and balanced Gran Turismo crank
3. Franspeed Super Clubman

GT186/200 Super Touring
As Fast Touring but with:
1. VHSH 30 flat slide carburettor or modified RD250 Mikuni TM34, elastic mount and SS clips
2. Gran Turismo auto advance / retard ignition system

GT186/200 Sprint
As Fast Touring but with:
1. Franspeed race or Super touring expansion chamber
2. Gran Turismo auto advance / retard ignition system

GT186/200 Super Sprint
As Sprint but with:
3. Franspeed race expansion chamber
4. Gran Turismo 8 plate billet clutch

Port timings and configuration
The table below lists the port timings for big block and small block kits configured with 107 or 110 con rods with 58, 60 or 62 stroke crank combinations.

Stroke 58 60 62 58 60 62
Deck 1.2 0.2 0.2 1.2 0.2 0.2
GT186, 107 rod GT186, 107 rod
Packer mm 0 0 1 3 3 4
Exhaust 171.1 172.6 177.7 170.8 172.2 177.3
Transfer 123.4 126.8 134.6 122.9 126.3 134.1
Blowdown 23.94 22.92 21.55 23.93 22.92 21.56
GT186, 107 rod GT186, 107 rod
Packer mm 0 0 1 3 3 4
Exhaust 179.2 180.3 185.1 178.8 179.9 184.6
Transfer 126.7 129.9 137.5 126.2 129.5 137
Blowdown 26.28 25.2 23.78 26.28 25.2 23.79
GT186, 107 rod GT186, 107 rod
Packer mm 0 0 1 3 3 4
Exhaust 173.6 175 180 173.2 174.5 179.5
Transfer 126.7 130 137 126.2 129.5 137
Blowdown 23.49 22.51 21.21 23.48 22.51 21.22


New for 2013 is the GT200 big Block for 200 cases (GT206 66 bore x 60 stroke). The big brother of the small block kit, this conversion utilises the same 350LC piston reed block and manifold series. It has larger and longer port durations which deliver exceptional performance. Supplied in 66mm bore this cylinder has the potential for 20 oversizes and piston combinations up to 71.5mm 245cc. Building procedure is identical to the small block kit.

Section index

1. Pre-fitting kit preparation
2. Installation preparation
3. GT186 Stock Touring Installation steps
4. Air box installation amendments
5. Carburettors, jetting & sparkplugs
6. Running in
7. Care and Maintenance
8. Tuning & performance
9. Disclaimer
10. Trouble shooting
11. Cylinder head specifications
12. Suggested specifications