THE BURMAN 2½ h p. ENGINE.

AT the present time, when most new productions in the small engine line act on the two-stroke principle, it is particularly interesting to find a well-designed and original small four-stroke. Such an engine is the Burman 2½ h.p. manufactured by Burman and Sons, Ltd , 89, Gooch Street, Birmingham

The enclosed overhead inlet valve and the crank case are the first points to strike the eye. The latter is of peculiar shape, for the bolt lugs are internal and their external radii are joined by neat curves so that the crank case can be wiped down with ease, and there are no ridges to collect mud. The valves are operated by a single cam, and the rockers are mounted in such a way that each has a long bearing surface on which to work. A Dixie magneto is mounted at a right angle behind the cylinder, and is driven from the camshaft through a single intermediate gear wheel. A large silencer is attached to the front engine bolts, and is supplied as part of the unit.

Dealing next with the cylinder, which has a bore of 76 mm. (the stroke being 65 mm.), the design is clean, and a clear air passage is left between the valve port and cylinder wall. The overhead inlet valve, complete with its seating and spring, drops into position from the top, and is held in place by a screwed dome. The inlet pipe casting, which is formed with the rocker bearings and cooling ribs, fits over this dome, and is held in place by a large diameter nut, and the rocker operates the valve through the medium of a small plunger, which prevents air leaks and takes up any side thrust. The inlet pipe is bushed to receive the inlet tappet rod, and the pipe is specially formed so that the bush does not choke the passage of the gas. Over the whole rocker gear fits an aluminium cap, precluding all grit, but removable for lubricating purposes by two small thumb nuts.

Novel Crank Construction.

Perhaps the most interesting feature of the engine is the crankshaft construction, which is quite unusual. The crank itself is a solid forging, hardened and ground to size. The crank pin is hollow, and through this is driven a pin which serves to locate the flywheels. The flywheels are internal, and the inner webs are set eccentric to their outside diameter, so as to provide correct balance. They are bored to fit the crankshaft, and have a hole to suit the positioning peg already mentioned. Consequently, they can be dropped into position and held on by locking nuts in such a manner as to ensure true running. This, unfortunately, is not a common feature on most inside flywheel engines, and materially affects high speed running.

The connecting rod carries a split big end of large dimensions, and the small end is also split and grips the gudgeon pin firmly, so that the pin oscillates in the piston. This method has much to commend it, for besides providing a much larger bearing area, no other gudgeon pin fixing is required. A ball bearing is fitted to the crankshaft on the pulley side, and all the other bearings are plain and of ample proportions.

Altogether the engine is an example of excellent design and high-class workmanship.

The Motor Cycle, December 24th, 1914. pp704,705