Laura Engine

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Laura model engines were used on the vast majority of Batavus mopeds in the U.S. and Europe

Laura M48 Motoren

The Laura M48 engine is an air-cooled single cylinder two-stroke Laura Motoren unit. 40mm (1.57in) bore X 38mm (1.49in) stroke = 47.78cc (2.91cu in). Maximum power 2.4bhp at 5000rpm. Cast-iron cylinder barrel and aluminum-alloy cylinder head. Compression ratio 7:1. 2 rolling-element main bearings. 3 ports, reed valve, Encarwi S22 carburetor.

U.S. and European models. Batavus M48 cylinder port timing / map mods

Thees M48 Batavus cylinder port,s power band mods Run WOT all day. 155Deg duration gives strong better than stock low end power with one cylinder base gasket with a duration 155 Deg or less over 156 you start lousing low end power.

Batavus M48 cylinder port timing / map mods

Port tuning for 4,500 to7,000+ RPM’s HP approx 4.2+. With stock red block. S-25 Encarwi Carb With mod’s 15+mm in 13mm venture 12.8mm out. Set float 12.5mm pin tip to top of float Jet #64. Stock intake Mod’s. 13mm in 12.3 mm out. Timeing .085”/ 26 Deg BTDC Stater at mid point +. Gap B8HS .021”.New points gap.0155”. Stock 26mm EX with power band Mod,s

Cut top of cylinder.024”.(Note Dome of piston shod rise 1mm=.039” above cylinder at TDC ). This shod give 16.6mm=.655”=21/32,s(NO LESS) top of piston dome to fin side/top of head where spark plug gasket sits on top of head at hole. ( You can use a tire tired depth Test it gauge cut sides to fit & Grate for timing to) Mill head To set gap Mill .?mm.0??” off head (Tip of spark plug must be 1mm=.039” or more away from top of piston dome at TDC) Approx 9.4 to 1 compression If you go higher it can over heat eng/stock piston/ping make you use less spark timing=Less power at 6,000+RPM’s

CK with 1 base gasket Head torqued to 8 ft lb (not 11 ft lb maul TYPO ? ) Don’t brake it. NOTE torque head in 4 steps - 1st torque to 2ft lb - 2nd torque to 4ft lb - 3rd torque to 6ft lb - 4th torque to 8ft lb and re torque to 8ft lb.

Displacement 47.75 cc. Bore 40 mm / 1.575”. Stroke 38 mm / 1.496”. Exhaust port duration 155 Deg=port height 13mm ovule shape Like Stew’s Head or a football width 24.5mm. Exhaust port opens 102.5 deg ATDC. Exhaust port opens 25 mm / .984” ATDC. (not top of cylinder) Port height 13 mm / .512”. Port width 24.5 mm / .964” = 60% of Bore. Polish and (taper exhaust port opening on piston side) don’t brake a ring. The exhaust port should open .984”=25mm=102.5 Deg ATDC. (not top of cylinder)

Intake / transfer ports Ports open 121.5 deg ATDC. Ports open 31 mm / .1.220” ATDC. (not top of cylinder) Intake / transfer ports duration 117 deg. Ports height….. 7 mm / .275”. Shape transfer ports like a long long tear drop pointing away from exhaust port. Transfer ports opening’s must not taper or point on exhaust port side of transfer port opening. Ports width….... 17 mm / .669”. Make the transfer ports point 25 deg’s away from exhaust port. Transfer ports need to open at 1.220” inches=31mm=121.5 deg ATDC. (not top of cylinder) Taper and deberr transfer ports. Save the last .5mm=.020”of porting for Hand touch up and Polishing.

Power band starts at 22MPH=3,800RPM's Kicks in at 25 MPH=4,500RPM's peaks at 37+ MPH=6,700 RPM,s Fads at 38 MPH and Fore stroks at 7,000 RPM’s = 39+ MPH with those Dam stock carb & reed’s

I hope this engineering witchcraft help,s you get your Bat going faster,

Crazy Wayne out

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Laura M56 Motoren

The Laura M56 is an engine found on the Batavus Regency and some Starflites. Daelim Motors produced mopeds under the name Trac, which used an identical replica of this motor in the mid 80's. The Trac M56 is officially the Daelim M56. Parts between the Laura M56 and the Daelim M56 are 100% identical and interchangeable.

Air cooled single cylinder two-stroke Laura Motoren unit. 40mm (1.57in) bore X 38mm (1.49in). NIKASIL plated aluminium cylinder and aluminum head, rolling-element main bearings. Reed valve, Encarwi carburetor.

U.S. models only.