125cc race machine specially prepared for ¼ mile sprint events at national level
Built on the lines of a 1966 Honda RC116 50cc twin using a 1978 Honda CB125T1 as a base
Very much modified by a very capable mechanical engineer with improved performance
Successfully campaigned by Sharon Wadkin-Snaith at Brooklands hill climb events
Attractive high revving and very noisy machine
First run in 2008 and subsequently continually developed for nearly 9 years including regular dyno testing by UK drag race legend Tim Blakemore, best time & speed: 15.61 @ 84mph.
Built expressly for ¼ mile sprinting at National Sprint Association events, nevertheless I styled the bike along the lines of the 1966 Honda RC116 50cc twin. Flangeless rims were used as they are a little lighter. Basis of the engine is a 1978 Honda CB125T1 for which Honda claimed 16.5hp, however they never exceeded 13hp on the dyno. This one started with 12.3hp and was slowly raised by skimming the head, porting and fitting the CBR250RR carburettors. The biggest gain came from major surgery to the exhaust ports to reduce their diameter, this alone gave a further 2hp. A misfire at 13,000rpm plus was cured by making titanium collet retainers allowing the engine to continue to a maximum hp at 14,000. The bike is currently geared to peak at 14,000 rpm in top gear approximately 50 metres before the ¼ mile mark. Initial acceleration is nothing short of astonishing; my wife having achieved 60′ times of 1.8 seconds on a number of occasions, quicker than our Honda CBR1100RR Blackbird drag racer! Sharon’s 100% committed riding style and accompanying howl from the exhausts led her to being known as ‘Hooligan’ by fellow racers.
Bike and rider caused a sensation at the 2014 Brooklands Museum Motorcycle Day, climbing Test Hill quicker than a Ducati Desmocedici RR! Urged on by the crowd she got a little carried away and like many other top sprinters came to grief after leaping the top of the hill. Bike and rider suffered some damage but a few months later were back in action running quicker than ever. The screen is still cracked as a result of this off and the machine has the patina of a bike that has been raced for 9 years.
Chassis: 1978 Honda CB125T with cut down headstock tube. Centre pressed steel section removed and replace with large diameter tube. Frame cut off behind rear shock mounts. Custom footrest and fairing mountings welded on. Custom made rear set footrests and controls in aluminium and stainless steel. Custom titanium swinging arm spindle and nut. Rebuilt standard rear shock absorbers with new parts in aluminium and titanium plus custom titanium nuts.
Forks: 1978 Honda CB125T, shortened re-chromed stanchions, shortened springs, modified sliders. Custom stainless steel spring retaining caps. Modified Derbi Senda 50 brake caliper on custom made bracket. Custom aluminium lower yoke with shortened steering stem. Custom aluminium top yoke incorporating ignition switch mount, aluminium crown nut. Custom billet aluminium clip on handlebars with modified Derbi Senda 50 master cylinder and custom brake lever. Modified junior MX clutch lever assembly with titanium pivot bolt. Active super quick action push/pull throttle.
Front Wheel: 1978 Honda CB125T hub in 18″ flangeless aluminium rim with stainless steel spokes adapted to take CB125TDC disc. This has been reduced in thickness and drilled. Custom stainless steel spindle and nut with titanium spacers. Standard mudguard with steel brace removed on custom mounting
brackets.
Rear Wheel: 1978 Honda CB125T hub in 18″ flangeless aluminium rim with stainless steel spokes. Aluminium sprocket with titanium retaining studs and nuts. Custom made titanium brake cam and spindle, aluminium brake lever and aluminium torque rod. Custom stainless steel spindle and nut, titanium spacers. All custom made brake rod and parts in stainless steel and aluminium.
Bodywork: Custom made seat in mild steel. Extensively modified Honda MT125R race fairing.
Engine: 1978 Honda CB125T, modified standard pistons, valves and advanced camshaft. Custom titanium collet retainers which allow 14,000rpm power peak. Skimmed and heavily modified cylinder head porting with major surgery to exhaust ports. Valve seats fitted by Serco and valves machined to match. Compression ratio unknown (a lot!) Cylinder head and barrel fins have been re profiled and all anti ring webs removed to replicate 1960’s Honda GP engines. Custom titanium cam cover bolts. Crankcases have large bore breather and internal passages. Recent new heavy duty clutch plates and springs. Alternator and kickstart mechanism removed. Custom ignition cover and auto advance unit mounting substantially reducing engine width. Custom sprocket cover/gear change shaft support. Engine mounting bolts and nuts custom made titanium. Custom oil catch tank in aluminium.
Fuel System: Custom steel fuel tank. Extensively modified outer carburettors from 4 cylinder Honda CB250RR mounted on custom inlet manifolds. Inline foam fuel filter. Custom made cable mounting bracket and choke control.
Ignition System: Dynatek Honda CB750 Dyna S pickups with modified backplate, Dynatek coils running total loss from 12V battery in the aluminium dummy sump.
Exhaust System: Custom made front pipes and custom made hydro formed open megaphones. Custom hand formed aluminium heat shields. Custom aluminium exhaust pipe collets and clamps. Total weight of exhaust system 2.2kg!
Maximum power output recorded at rear wheel 17.4 @ 14,000rpm, however retarding the ignition incrementally reduced this to 16.9hp but gave a substantial on-track performance boost. Total weight ready to race 80kg, 47kg lighter than a standard CR93!
The bike comes with a spare head fitted with custom manifolds together with other spares. There is substantial scope to improve performance as the bike still uses a standard cam which gives a smooth power curve from tick over. An aluminium tank and seat would reduce weight even more. This is an ideal machine to use at classic racing demos where noise restrictions are not enforced