BSA B25 Trials

15 Фев 2015 | Author: | Комментарии к записи BSA B25 Trials отключены

The later BSA B25 is not very often for trials, partly because it is too new for events, and partly because of the design. However the engine is a improvement on the previous C15 (just as the B44 is a better engine than the and the frame is slimmer at the rear and has the adjustment at the swinging arm mount.

measuring a Can-Am 350, 350, SWM TL320, Montesa 349, Suzuki RL250 and an Climber I decided on the frame Settling on a wheelbase of 52, a head of 27deg, and footrests mounted below and behind the swinging arm on a level with a line the wheel centres.

First I the swinging arm by 1.25 by moving the wheel mount forward to the suspension mounting. The frame was placed in a jig to ensure that all are to required parameters. The entire top of the frame which forms the oil and rear mudguard mounting was

The front down tube was heated just above the mount and given a very bend. The tube was then just below the steering and bent down until the fork angle was achieved. A new top made from thin 1.34 Chrome-Moly tubing was welded into place, and plates were added the steering head to complete the frame loop.

The tubes from the swinging arm mount bent inwards and slightly to slim the rear subframe. The new unit top mount was bolted the jig to hold it in the correct position it was bronzed into place. this was done on both the suspension top mount was connected to the frame with 0.75 tube.

Rear mudguard were bronzed on, and the frame was except for a couple of mounting and the footrests.

Various spacers and brake had to be made up for the Montesa Cota 348 which were used, having been laced new spokes. An alloy oil tank of 1 Lt was fabricated and placed across the just above the swinging arm

The engine was left in standard with the exception of PVL electronic smaller engine and gearbox and a compression plate under the to reduce the 10:1 compression to a more trials friendly In order to help with the (idle) and to make the engine responsive at low revs a small Mikuni carb was fitted on a manifold. A alloy silencer in the UK was added both to quieten the note, and also to tuck it the frame and clear of the riders

I am very pleased with the which performs to a very standard, certainly comparable most of the 70s trials bikes. It and handles as well as those and weighs only 205lbs. The is very responsive with of low end torque to provide tremendous in all sorts of conditions. With modifications to riding style to for the lesser ground clearance it very competitive.

This bike has the standard British of rear brake on the left and on the right, but for future models will have the opportunity to the rear brake on either

The B25 as made by BSA weighing 275lbs and a 20 front wheel.

Remade by Motorcycles.

The modified frame, and ready to paint.

Shortened arm with two mounting points for the and below that for the chain

Here the new rear subframe and mounts can be seen. All joints are welded (this is not the same as

The modified frame has a much profile.

A number of pieces nickel plated using one of home plating kits.

other bits. Some some bought, and some

The engine fitted with PVL ignition from Sammy Products in the UK, and a compression plate to the 10:1 ratio to 8.5:1.


The brake torque arm fitted to one of the lugs with no modifications but a bracket for the cable had to be made.

The brake is cable operated on the side (where it should

Chain tensioner is from Miller Products. Very but unfortunately it was kinked to the wrong for my application so little professional force was needed to get it right. The brake torque arm combines the stop.

The beauty of the PVL system, apart first kick starts, is the that it completely replaces the with only two wires up to the coil. These wires routed up through the front tube which used to be a of the bikes oil tank.

The carb is one of those pit bike things. a 25mm choke it actually at the throttle slide but with jet tuning it works really As the bolt holes are the standard 1 7/8 and not the Amal 2, a manifold had to be made.

also allows a longer manifold which has a noticeably effect on the engine.

An alloy oil of 1 Lt (just over a quart) was made. I did the cutting and folding and Komer of The Tryals Shop did the

The silencer came from the UK. It is and beautifully made but little

As you can never find a tree you want one, even in the I fitted a propstand to the Mk II.

It not only really pretty but it works too. Mick Andrews a day riding it on a recent visit and he all of my sections on it.


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