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The Burman Gearbox

The Burman Gearbox

Operation & Maintenance

The BAP-type Burman gearbox fitted to the Meteor and the Comet models is a pleasantly simple and robust unit. Although some users advocate grease for lubrication, or a mixture of oil and grease, it is usually found that a heavy engine oil is satisfactory. The grade to the now-discontinued SAE 60 viscosity rating is about right. The presence of grease means little in the way of additional lubrication. The rotating gears cut a cavity in the grease, flinging it all to the outside of the interior where it effectively seals the box against leakage. The addition of graphite or molybdenum disulphide is considered advantageous.

An unusual trick of this box is a tendency to jump out of third gear, especially after repositioning of the pedal. The cause is the pedal, when depressed to select third, fouling the indicator tab. The tab can be bent out of the way or removed; it is doubtful if it serves any useful purpose except to the novice. The Burman kickstarter return spring is of the coil type. Two turns from the static position of the spring should provide sufficient tension for the crank to return in a positive manner.

The gear-selecting mechanism can be timed for correct operation once the end-cover has been removed. Engage the tooth marked '0' with the mark on the camshaft pinion.

The clutch push-rod is in two parts, with a ball between. The clutch adjuster is locked by a light-alloy cap on the outside of the cover which is retained by two cheese-headed screws.

Uncertain engagement of gears can be caused by wear on the rocking pawl mechanism, or it is possible that the spring in the springbox may be weak, or even broken. Further difficulty will probably be due to worn striker forks, which can also cause top gear to be thrown out under load. The main driving gear bush can move towards the kickstarter side, so preventing full gear engagement.

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A new bush should be fitted. Transmission noise in third gear is usually due to wear on the layshaft fixed pinion and/or the main driving gear which engages with it; check the layshaft bush. Noisy bottomgear selection from rest is certainly due to clutch drag.

Broken pinion teeth may he the cause of, and can result from, bent shafting in the box. Although a skilled man can straighten the shafts, a private owner is advised to fit new components. End-play in the mainshaft can be caused by slackness of the kickstarter pinion nut, or by wear in the small bearing in the kickstarter case. Provided that the wear has not become excessive before detection, play can be taken up by placing shims between the bearing and the housing.

There is bound to be a trace of movement with the clutch. But more than this is due to wear of the clutch hub bearing. If the tracks are in good condition new rollers can be fitted.

A drain plug was fitted to the Bunman box after 1951 and oil should be changed every 5,000 miles. The capacity is 1-1/2 pints. A grease nipple is fitted for lubrication of the selector mechanism. For the boxes not equipped with drain plugs it is impossible to do more than add an eggcupful of engine oil every 2,000 miles and occasionally a little grease. The box seems to thrive on this.