Racing CB500T's

HONDA'S CB450 precursor to the CB500T was a natural choice for racing conversion, with all its high tech features.

IN the USA 2 450's were entered in the 1967 Daytona Experts race under the Team Hansen banner, finishing 10th. and 12th. These bikes had factory support, as the idea came from the service director of Honda USA and dealer Bob Hansen. The level of support was, shall we say, pretty comprehensive. The bikes were built by Honda and featured many one off parts, in fact it has been suggested that the only standard castings were the head and barrel.

THAT same year the Amateur race was won by another 450, the Precision Machining backed entry. Precision Machining fitted their own cams giving 8.4mm lift and timing of; Inlet opens 40°BTDC, closes 60° ABDC. Exhaust opens 65°BBDC, closes 50°ATDC.

Interestingly engine tuner Jim Kibblewhite modified the preload on the torsion bars to allow higher revs without valve float. This was achieved by grinding a spline tooth off each torsion bar and then swapping left for right. The effect was to increase closing force with the valves fully open, to 175lbs. Their rider claimed to have reached 12000rpm whilst slipstreaming faster bikes.

It turned out that this was an intermediate solution, as the torsion bars modified in this way tended to have a dramatically shortened working life!

Compression ratio was 10.4:1, achieved by modifying standard pistons and standard carbs were used after trials with 35mm Keihin racing carbs.
Precision machining produced a free data sheet on the modification, and I wonder if this is still available as Kibblewhite Precision Machining are still with us ( click here to visit their web site ). Indeed none other than Brian Johnson uses their parts in his awesome Top Fuel Bike.

FROM the same era the Wilkinson-Peterson 450 flat tracker was very successful.
This used welded up and machined standard pistons for compression ratio of 11.25:1. Kenny Harman cams were fitted though the torsion bars were not modified. However due to cam lift, material had to be removed from inside the cambox and new, shorter, valve guides fitted.

The bike used 1.0625" Amal carbs and very short exhaust pipes and megaphones. Right hand engine cover was replaced with a new fabricated item, as the centrifugal oil filter was discarded, and gearchange shaft brought out on the right (left handers only in flat track). The engine produced 53bhp at 9750rpm.

MEANWHILE in Europe a number of 450 based racing machines were built. The best known of these being by Fritz Egli and Marly Drixl, both of which were taken out to a full 500cc. Terry Dennehy was very successful on his Drixl machine and finished 4th. in the 1969 Italian Grand Prix at Imola.

The popularity of classic racing in the latter part of the last Century saw a renaissance for Honda twins. CB500T based bikes have become very successful and the Henning Honda was a high profile winner, though the engine was a combination of 450 and 500 parts to fit the race regulations. Follow the link on our errr...... Links page to see how they did it. Other sites of interest include M3Racing who supply lots of expensive bits including 11.6:1 pistons.