Building a Works Bucket Racer

By Ken Lindsay

This is the story of building my bucket racer 2.

Work started with a standard CB125N frame. It was attacked with a hacksaw, angle grinder and oxy, stripped of all unnecessary brackets etc. and looked pretty sad sitting on the bench. Lugs were welded to the frame approximately 100mm above the swingarm pivot, which served two purposes, foot peg hanger mounts as well as the very important bracing of the swingarm pivot. A new rear fuel tank mount was welded to the frame, 25mm rearward of the old mount. 5mm thick shock mount plates were welded to the frame (as the standard rear shock mounts were previously cut off) for a “bolt on” type shock mount system. A jig that I had made some years ago was used to construct a 25mm mild steel box section swingarm, complete with provisions to use snail cam chain adjustment. Bronze bushes with stainless inserts were made and fitted.
 
At this point I made up a jig to aid construction, which was basically two lengths of aluminium channel used to clamp the wheels square and in line.
 
The rolling chassis was then assembled, ie: frame, swingarm, triple clamps, forks wheels and a dummy engine (crankcases with a gearbox output shaft). It was then a matter of making alloy wheel spacers and getting the wheel alignment correct as well as chain alignment. Needless to say this was quite time consuming, however as you would expect it would prove to be time well spent. At this stage the rear of the frame had been supported by a stand, as no top shock mounts existed hence no shocks fitted to the bike.
 
The next step was to set up the geometry to the specifications I required with adjustment either way. I wanted something that steered similar to my old bike but with added stability. This meant a careful selection of triple clamps (offset) and rear ride height. The triple clamps I selected were a top clamp from a Honda XL185S and the bottom clamp from a 1974 CR125M. There were various reasons for this selection. (A) The offset was to my requirements, (B) The bottom CR125M clamp was obviously the same dimensions as a bottom XL185 item but made from aluminium as opposed to steel (lightness) and (C) I had them lying around (cheap).
 
The triple clamps were made for 31mm forks and the forks I selected to use were 27mm CB125N items, simply because I like their performance (with minor internal & external modifications) at the time, they are very light and the cost (I had them lying around). I had to machine up a set of four aluminium sleeves so the clamps would accept the forks. The forks were then fitted and set in the “middle” of their adjustment range in the clamps and using an “angle meter” the steering head angle was set to the required angle by jacking up the back of the frame. Once this was set up the rear shocks were bolted onto the swingarm using specially machined alloy bolts. Measurements were made for the “bolt on top shock mounts”. While in the process, five sets of these “bolt on shock mounts” were machined up from billet aluminium all varying in measurements by 10mm. These would be used to vary the ride height of the bike by simply unbolting the shock mount and bolting on another set. Adjustment range is 40mm and can be changed in about 5 minutes. At this stage, the bike was stripped down and the frame and swingarm sent off to be powder coated black.
 
While the frame was off getting powder coated there were various items I had to make for the machine which included a one piece fork brace, foot pegs & foot peg hangers, rear brake pedal, gear lever, front brake caliper bracket, rear brake caliper bracket, rear master cylinder bracket, all of which were machined and/or fabricated from billet aluminium. Fairing mounts, seat mounts, gear linkage and bolt on fuel tank mounts were also made. I polished all these items as well as the front forks and triple clamps.
 
After receiving the frame back from being powder coated, the rolling chassis was assembled. This included fitting the swingarm, triple clamps, forks, shocks, wheels, handlebars, brake master cylinders & calipers, fork brace, foot pegs, rear brake pedal, gear pedal, fairing mounts, seat mounts and fuel tank mounts.
As mentioned previously, Brake caliper mounts etc. were being made to suit the calipers I selected to use. I ended up with a VFR750 caliper mated to a CBX250 (12mm) master cylinder on the front and a CR125 caliper & master cylinder on the rear.
 
Once the rolling chassis was completed, it was then required to modify the seat to fit as required. This meant a couple of visits from my friendly spray painter & repairer, who cut, shaped and fibreglassed the unit for me. The seat started life as a 1997 Marco Melandri GP Replica and really only needed a bit of reshaping to fit. Once the seat was finished, I then needed to fit some sort of side covers and I ended up using slightly modified CB125T covers. They fitted neatly, weighed nothing and cost nothing, but they finished off the whole package beautifully. A Moriwaki GP80 fairing was selected to use and fitted nice and neatly to the bike. Finally I fitted a VT250 front mudguard to the bike and it was perfect and again this fitted beautifully. Once I was happy with the way all the body work looked & fitted the bike, the fuel tank, fairing, seat, side covers & front mudguard were all sent off to the painters. What would come back was a brilliant job obviously painted in the now well known “Ken Lindsay Racing” colours of Blue, White & Red.
 
In the mean time the engine was built based on XL185 Crankcases Cylinder & Head, CB125 Crankshaft, CB100 Gearbox & XL185 Clutch. The engine, exhaust & carburetor were fitted in the chassis along with all the electrics. The body work was then fitted to the bike and the machine was ready for the track. As with any new bike, some changes have been made and there have been a few small problems ironed out.
 
Since the bike was built, the triple clamps have been changed from the CR125M / XL185 combination to a set of machined billet aluminium ones using a 5mm different offset & the forks have been replaced with a 32mm Item off a Suzuki GT250X7.  The swingarm has been changed for a longer unit by 20mm. The engine crankcases have been changed to XR200 with 6 speed gearbox. The front & rear brake calipers have been replaced with twin opposed piston Brembo’s & the bottom half of the fairing removed to comply with 2004/2005 rule changes.
 
The Bike is very competitive & an absolute joy to ride. Refinement of the engine & chassis is always ongoing.

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