Monday, 23 January 2017

The Yamaha racing frames of Jim Lee

It is an often asked question as to which frames Jim Lee made for the production Yamaha 2stroke race engines. Many times frames have been incorrectly identified through a lack of knowledge and falsely attributed to his hand. The following blog is an attempt to catalogue his work in this field.

Jim was clearly born with a welding torch in his hand, but had a wonderful ability when it came to all aspects of fabrication. His skill was not only in the actual joining of the parent metal, but also in the visual effect of the finished product. It had to both ‘look right’ and be easy on the eye. Unless requested by a customer to do things differently, the former qualities gave his work a distinct feel and have left a signature for all to see.
By the mid 1960’s Jim had fabricated racing frames suitable for a huge variety of race engines. In fact it was his ability and willingness to take on ‘one-off’ jobs that had attracted his services to people such as Reg Orpin, Peter Williams, Dave Simmonds, Bill Bancroft and Paul Dunstall to name but a few.

Series 1 frame 

These frames were made using 17 SWG Renolds 531 tubing and were fillet bronze-welded at the joints. Jim used a gas-fluxer fitted in the acetylene hose to the torch and it is fair to say he was generous with the bronze fillet applied. The frames were generally of a simple duplex design and as Jim used a thinner gauge tube than the accepted norm, were considerably lighter than proprietary units. Jim’s constant quest to save weight resulted in him using brackets and gussets that were minimalistic in design and in many cases barely up to the job required. As a consequence his frames suffered badly over time, with fatigue and fracture cracks limiting their useable life. It is often said that no two similar frames are identical, as Jim did not use a complete frame jig, the tubes being bent to chalk markings on the workshop floor.
Four distinct series of frame were made from the period 1965 to 1970 and are described in detail below.

Series 1                                                               
This was Jim’s original design for an improved race frame which could be fitted with a Yamaha TD1B/C or Suzuki TR250 engine. The frame was supplied along with clip-ons, footrests and swinging arm at a cost of £65.

Series 1 frame modified by Jim Lee to fit a Bultaco 250 engine

The distinguishing features in this series of frame are as follows:-
The frames are fabricated in 1” diameter x 17 SWG Renolds 531 tubing.
The frames are bronze-welded throughout.
Single thickness plate to SA pivot gusset.
Steering head brace tube is near to being in line with the main frame tubes from the SA gusset plate.
Single thickness plate to front engine mounting gusset.
Stud brazed into seat tube for upper suspension mounting.
Splayed seat tubes at upper suspension mounts return slightly beneath the seat.
Tubular footrest support brackets.
Fabricated ‘D’ section swinging arm with ‘pull back’ adjusters to the rear wheel spindle.

Short steering head brace

Splayed seat tubes and upper suspension mounts

Fabricated 'D' section swinging arm with pull-back adjusters

Series 2
This was the later version of Jim’s race frame and was intended to be fitted with a TD2/TR2 Yamaha engine. Although the attention to bracketry and ‘boxing in’ of the SA pivot and front engine mounts were sorely needed, the overall design of the frame is not as good as the original series 1 version. Quite simply the more ‘open’ layout of the main frame tubes and general lack of triangulation meant there was no longer the same degree of stiffness between the steering head and SA pivot. This change in frame design however allowed a taller engine to be fitted and removal for maintenance was considerably easier. Jim by now had expanded his business considerably and no longer made every frame himself. He was ably assisted by both Neil Procter-Blain and Brian Earnshaw in the fabrication of his frames and it is clear to see that the grey frame shown below is not of his hand.

Seies 2 Yamaha TD2 Jim Lee frame

The distinguishing features in this series of frame are as follows:-
The frames are fabricated in 1” diameter x 16 SWG Renolds 531 tubing.
All joints of the frame are bronze welded.
Fully welded boxing of SA pivot gusset to frame
The steering head brace tube extends halfway along the top tubes and is not in line with the main frame tubes from the SA pivot gussets.
Fully welded boxing of front engine mountings.
Double-sided plate support at upper suspension mounting.
Seat tubes splay after the rear cross-brace and widen towards seat mounting.
Fabricated plate footrest support brackets.
Fabricated ‘D’ section swinging arm with ‘snail-cam’ adjusters to the rear wheel spindle.

Long steering head brace

Fabricated 'D' section swinging arm with cam adjuster location

Splayed seat tubes above upper suspension mounts

Series 3
These frames were manufactured by Jim Lee and supplied as a frame-kit to Padgetts of Batley. The frame was similar to the Yamaha factory unit, but with a 1 ½” longer swinging arm and could be fitted with Yamaha TR2, TD2, TD1B/C engines. The complete frame kit included forks, tank, seat and rear dampers. It was priced at £179 and purchased direct from Padgetts. 

Jim had taken the brave step to invest very early in MIG welding equipment and was one of the first of the ‘bespoke’ frame makers to go down this route. Primarily it was because he wanted to increase the production of frames for Dalesman and Wassell. Following a series of tensile welded-sample tests carried out at Aston University, it was clear that Renolds 531 could not be reliably MIG welded. This prompted the move to Cold Drawn Seamless Tube as the frame material to be used with this welding technique. Mick Grant assisted in the jigging and welding of these frames.

Series 3 Jim Lee fabricated Padgett Yamaha frame.

The distinguishing features in this series of frame are as follows:-
The main frame is fabricated in 1” diameter x 16 SWG CDT (cold drawn seamless tube)
The seat sub-frame in 7/8” diameter x 16 SWG CDT (cold drawn seamless tube)
The frame was MIG welded throughout.
The frame was fully bracketed to accept all STD Yamaha ancillary parts.
Fabricated box-section swinging arm, similar design to STD Yamaha item but 1 ½” longer in length.
The main frame tubes from SA pivot gussets are not of uniform radius as on STD Yamaha frame.

Swinging arm gusset and Yamaha ancillary mounting points

Steering head brace and tank restraint mounting

Rear seat hoop and upper suspension mounts

Series 4
These were ‘spine’ frames and of a completely different design to anything that had been seen or done before. Jim built a special Yamaha TR2 as a 'works' bike for Mick Grant to ride during the 1970/71 seasons. This was built as a 'one-off'' with 'no expense spared' and at that time Jim had no plans to market or sell replica versions to paying customers. It was innovative in using a large diameter straight tube as the spine of the machine. This was bored at the correct angle and the now usual long steering head tube passed through and brazed in position. The same was done at the swinging arm pivot, ensuring that both steering head and swinging arm remained in their relative positions at all times. A pair of tubes ran from the massively braced steering head, beneath the engine and returned to join the seat rails at the top suspension mounts. An extended swinging arm pin passed through the main spine, swinging arm bushes and a brazed clamp on either of the cradle side-tubes. This arrangement greatly increased the stiffness of the frame.

Mick & Jim with his Yamaha TR2

As it turned out, the combination of Mick Grant and the Jim Lee Yamaha were an outstanding success and because of this Jim offered to build replica frame kits for interested parties. The price of the rolling frame was approximately £200 depending on the actual specification.


The distinguishing features in this series of frame are as follows:-
The main spine is fabricated in 3” diameter tube.
The engine support tubes are 1” diameter x 17 SWG Renolds 531.
The seat rail tubes are ¾” diameter x 17 SWG Renolds 531.
The frame is bronze-welded throughout.
The engine is rubber mounted throughout.
An extended swinging arm pin passes through the main spine and is clamped to cradle side-tubes.
Tubular swinging arm fabricated in 1 3/8” diameter x 16 SWG Renolds 531.

Heavily gussetted down-tubes

Main spine and diverging seat rails.

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