Version of the proven BGM177 cylinder for Vespa Largeframe 2-channel engines from approx. 1962 to the 1970s.
This includes, for example, the Sprint, Sprint Veloce, Super, VNB, VBB, GT, GTR, VGLA (T4) and VGLB models.
Go for it: bgm077T2
PERFORMANCE PLUS FOR EVERYDAY USE
The BGM177 cylinder is a very powerful, durable conversion cylinder that is fully suitable for everyday use. It covers a very wide range of possible applications. By simply replacing the cylinder, you can more than double the power of the 125cc standard engine and surf the big torque wave with ease. In the same way, exactly the same cylinder can transform the engine into a beast with over 20 hp if it finds the right environment (carburetor, exhaust, crankshaft). The cylinder therefore offers beginners a perfect basis for further expansion as required.
The bgm PRO 177 replaces the original cylinder, the conversion is simple and easy to overhaul if necessary. With its large displacement of 177cc, the BGM PRO 177 always offers a superior and relaxed riding experience. The engine drives as powerfully as a 200cc machine, but with the same reliability and durability. It achieves this by operating in the same speed range as a standard engine. Low consumption values and the associated long range are a further bonus of the BGM PRO 177 cylinder. The cylinder is designed to be compatible with standard components. The only adjustment that is made is a change to the BGM1770NEJ carburetor jetting and a 3300009 spark plug with adapted heat value.
FEATURES
The BGM PRO 177 cylinder is a hard ceramic coated aluminum cylinder with a 63mm bore. The coating (nickel-silicon-carbide) ensures an extremely hard and durable bore. The piston has a high silicon content. As a result, it has a lower thermal expansion, is more wear-resistant and thermally very stable. Two 1 mm thick piston rings minimize friction and thus increase performance and speed stability.
- Cylinder material: aluminum
- Raceway: coated with nickel-silicon carbide
- Bore: Ø 63mm
- Displacement 57/60mm Stroke: 177/187 cc
- Piston: cast piston with high silicon content and two 1mm steel piston rings
- Recommended crushing edge: 0.8- 1.2mm
ASSEMBLY
The adaptation of the actual BGM177 cylinder with 3 overcurrent channels to an engine with 2 overcurrent channels is done using the supplied spacer, a 2mm aluminum gasket that covers the third overcurrent channel.
The cylinder is prepared for the use of this 2mm spacer. In addition to the spacer, the supplied cylinder base gaskets are used between the spacer and the cylinder when installing the cylinder in order to set the desired pinch dimension.
CYLINDER HEAD
The BGM1770H cylinder head is CNC-milled from solid material. The combustion chamber is sunk 4 mm deep into the cylinder for perfect centering. Dhis makes it considerably easier to adjust the pinch edge and ensures a perfect sealing between cylinder head and cylinder is guaranteed. There is a thread in the center for mounting a temperature sensor. The compression ratio was deliberately chosen to be low at 10.3:1, which means that the pinch point can be lower than with comparable cylinders. Due to the low, possible crushing edge, the engine reacts more clearly to changes in the jetting and ignition setting. This the adjustment of the engine is much easier.
In the detailed data sheet which is enclosed with each cylinder, you will find additional information on adjusting the various setups.
FURTHER TUNING
The cylinder kit is designed as a plug 'n play solution. However, the cylinder still offers a great deal of upward potential with full reliability. With a 24mm carburetor of the 200cc models and a BGM Big Box Touring exhaust, the power is already around 15 hp and the torque is 17 - 19 Nm at the rear wheel. The BGM PRO 177 responds very gratefully to all performance-enhancing measures such as
- A suitable exhaust system (BGM BigBox Touring(BGM1011TR2), Polini Box (P2002018))
- A larger carburetor (BGM PRO Faster Flow SI24 (BGM8570))
- Crankshafts with extended intake control angle (BGM031120G) and/or more stroke (BGM031121G)
- An optimized pole wheel (BGM8036RT)
- Optimization of the intake tract (milling of the intake port)
- Enlargement of the overflow channel surfaces in the cylinder base sealing surface and in the motor housing (The overflow channels on the cylinder base have a sprue. This means that the channels on the cylinder correspond to those on the engine housing. The sprue can be easily removed to use the full cross-section of the channels)
MORE DISPLACEMENT AND POWER
The cylinder is already prepared ex works to be used with a crankshaft with a larger crankshaft stroke (60mm instead of 57mm as standard). This increases the displacement to a whopping 187cc and the performance-determining timing angles of the ports are increased. With the appropriate crankshafts and further modifications to the engine, the cylinder can also be easily fitted with an even larger stroke (up to 64mm, see crankshafts KINGWELLE) can be used. It then reaches the full 200cc, but requires intake control via a diaphragm intake due to the necessary crankshaft.
IGNITION
The BGM PRO 177 cylinder is already very efficient and powerful thanks to the CNC cylinder head with a modern combustion chamber and close-tolerance squish edge.
The contact ignition systems of the typical Vespa 2-channel engines can still be used together with the BGM177 2-channel cylinder, provided they function perfectly and are regularly maintained. However, a conversion to a maintenance-free, electronic ignition is highly recommended. Special ignition modules or a variable ignition advance are not necessary for high performance and reliability. A simple static ignition setting to 19° from TDC is recommended. We offer suitable ignition kits for converting the contact ignition system. For Vespa Sprint models as well as for Motovespa and engine concepts where a crankshaft with the PX alternator cone is used.
CARBURETORS
The original SI20/17 carburetors of some Vespa models are no longer adjustable in the necessary range for the BGM177. Therefore, at least the modern SI20 or better the SI24 should be used.
CONTROL ANGLE
- 57mm stroke: overflow 118°, outlet 171° (with foot gasket 0.2mm, no head gasket)
- 60mm stroke: overflow 123°, outlet 173° (with foot seal 0.2mm, head spacer 1.5mm and 2mm)
- (head spacer for 60mm stroke not included, optionally available, see accessories)
INLET / ROTARY VALVE
Most 2-channel motor housings have a very short intake control angle. The BGM177 can cope with these small timing angles, but the short timing cross-section reduces the possible performance of the cylinder.
A clear recommendation here is to adjust the intake timing angle during the next engine overhaul or directly when setting up the engine. Intake timing angles of approx. 100° to 105° from TDC and 55-65° off. TDC are our recommendation for a powerful touring setup.
For very sporty engine designs, the intake can be set to 110° TDC and up to 75° TDC. This shifts the available torque by a few hundred revolutions in the direction of higher revs.
The bgm Pro milling template is suitable for bringing the intake to powerful touring control angles.
GEARBOX
Many customers subsequently lengthen the transmission ratio even in low power expansion stages in order to make even better use of the newly gained engine power. This is done by simply replacing the clutch pinion. This is relatively easy to access after removing the rear wheel and the clutch cover behind it. Alternatively, it is also possible to change directly to a reinforced clutch type (see accessories). The gears can then be accelerated significantly further and the achievable top speed is increased. The engine has so much power that acceleration is usually better because you don't have to shift as much or as quickly.
In general, the gear reduction can be longer than usual in the 177cc class due to the high torque. If a touring-oriented exhaust with early support is used (BigBox Touring, Polini Original Box), a PX125 should be fitted with at least one clutch pinion with BGM6823S 23teeth should be used on a PX125. We stock these specifically for the original primary wheel with 68 teeth (see accessories). Engines with a long stroke shaft and/or 24mm SI carburetor also easily pull a 24/65 reduction on PX125 gearboxes.
Depending on the gearbox, the bgm primary with 24/63 or 23/64 BGM6564W is the recommendation.
CONCLUSION
Universally applicable plug 'n play cylinder kit with early power, wide rev range, reliability like an original cylinder, low consumption values and therefore an unbeatable price-performance ratio!
bgm077T2
EXAMPLE ENGINE
Here is the performance diagram of a VBB2T engine converted in this way.
- Intake adapted with template, results with the crankshaft used 108° v.Ot. and 50°n.TDC.
- BGM1772BS20 Spacer cylinder base 2mm
- BGM1770HS20 Spacer cylinder head 2mm
- BGM1770G Gasket cylinder base 0.6mm (=QK 1.1mm)
- 7676246 Stroke 60mm
- BGM1010TR2 Exhaust BGM BigBox Touring V2
- BGM8570 Carburetor bgm Pro SI Fasterflow 24mm
- BGM666SP1 Ignition set bgm Pro electronic, ZZP 18° from TDC
- Overcurrent channels not machined (not in cylinder and not in housing)
- Carburetor with standard 9021005 LML air filter, VBB carburetor sump/carburetor sump cover
- BGM2577 Intake hose pgm Pro PX Lusso
Due to the selected intake time, the torque is available pleasantly early early.
At 5700 rpm, the engine achieves an impressive maximum torque of over 19 Nm for its displacement class, making it ideal for a powerful engine that can cope with any mountain pass.
Thanks to the high torque and the wide power band, we have equipped the original transmission of the VBB with a primary bgm Pro 23/64. This enables a top speed of approx. 120 km/h on the flat on 8-inch tires.
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