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Royal Enfield racers finished 7th and 8th in the 250cc and 500cc championship tables at the end of the Vintage Motor Cycle Club Racing sections 1997 seasons. I had the pleasure of riding a 1958 based Crusader and a mid 50's Bullet 500 throughout a season of extremes.
Bullet 500
The Bullet is a modified road machine which I purchased at the start of my second year of historic racing, 1995. It was previously owned by David Stevenson who lent it to a friend who wished to give classic and vintage club racing a try. He took a road going machine in unrestored condition with the usual few bits of tinware missing and turned it into a middle of the field racing bike in 1990-94.
The main modifications were to the engine as the owner did not want any irreversible modifications made to the frame.
The crank was lightened but big end and con rod retained as standard. The barrel was shortened by 5mm at the base, one fewer fin , and a BSA B50 piston used in the +40 rebored barrel. This gave a compression ratio of about 9:1.
A Lucas Racing magneto SR1 was fitted and a special exhaust mounted to the left side of the machine was made up in mild steel. It is easier to achieve good ground clearance on this side and there are less left hand bends on clockwise circuits.
A twin sided front hub was used laced to an Akront 18" alloy rim. On the rear a Bantam hub was used as this enabled relatively quick and easy use of a range of rear wheel sprockets. A neat glass fibre humped racing seat was fitted and the original late 50's petrol tank completed a rather good looking café racer style machine.
First season
My first outing was at Cadwell Park in 1995 which was fairly uneventful . As was typical of the season the bike was slow and gear changes problematic .Too fast and it missed a gear or found a false neutral ! There was much Castrol R on the outside of the engine but everything held together to enable me to have some fun at the back of the field .My best result came at Three Sisters where for one race everything went right (I still haven't worked out why ! ) and I came 7th .However on the second day of the weekend meeting the Bullet would not fire up and that was as good as it got . Subsequently I discovered that the inlet valve was not seating fully due to a bent stem. This was to be a portent of things to come .
Improvements for 1996
During the winter I worked on the oil leaks to the head region and fitted a new inlet valve .The head was machined and lapped in to allow it to run without a gasket .At the same time the pushrod holes in the head where countersunk to take "O" ring oil seals. This worked well but disaster soon struck at Snetterton in May 96 .In the quest for more power I fitted some reprofiled cams which the previous owner had had made. These gave about 3mm extra lift and slightly longer opening duration. There seemed to be more speed but this was short lived as there was a coming together of piston and valves during a bit of over revving on Senna Straight resulting in a destroyed; piston, valves, guides and major damage to the head.
In the opinion of a well known RE dealer near Letchworth the head would make a good doorstop! But undaunted I asked around and found a small firm who took the job on. They cleaned up the dents in the head and fitted new inserts to both valves, the inlet a larger than standard scrambles one, guides, plug insert and blanked off the decompressor hole. All parts came from the ever helpful Alan Hitchcock. The barrel was rebored, by then to +60 ,and a +20 Gold Star piston fitted giving a compression ration of about 8.25 : 1.
First the good news!
The repaired and modified machine worked well and my lap times and placings were improving until the July meeting at Cadwell when a metallic " ping " was heard on the long Park Straight. Funny how it always seems to be on the fast bits . Being just slightly more cautious by then I cruised into the pits to investigate. There were signs of the inlet valve touching the piston again although I had been careful to check clearances using the plasticine method. Later I found that the big end had some play allowing closer contact between head and piston than is desirable. The head was worked on by the owner of the Crusader I also ride and a replacement needle roller big end and steel con rod fitted by Rick Gibbon. At the next meeting, Three Sisters, all held together beautifully except for the rider and machine who parted company at Lunar Bend , resulting in broken collarbone. That was it for 1996. The prang also bent the fork stanchions but I didn't realise this until well into the next year.
1997 season--Last away ----good finish.
The 1997 season started miserably. The initial problem of poor gear changing returned taking two race meetings to sort out. What it came down to was very careful adjustment of the plates which control the amount of movement of the ratchet assembly and making sure the clutch frees completely. Once set up properly false neutrals even at racing speeds can be limited to one or two a race! By my reckoning a missed gear changed means about 50 yards advantage to the other riders.
Other mods made throughout the season have included attempts to lower the centre of gravity of the bike by reducing the length of the fork springs by 25mm and repositioning the rear shockers to lower the seat height. This improved handling but reduced ground clearance necessitating moving footrests, brake lever and exhaust to slightly higher positions. I am not sure this is all worth it and may revert to the earlier setup on the rear.
There is a wide gap between third and fourth gear in the standard box and I have attempted to create a close ratio box by changing first gear and fourth gear pinions. In the standard box both pairs have 18 and 30 teeth. After much searching for two pairs of 19/29 I managed to purchase from different sources one pair and a single 29 tooth kickstart pinion. The 19 tooth pinion can be used on the main shaft or layshaft. However it would not mate up with the 29 tooth kickstart pinion but strangly enough the standard 18 tooth one would. So I ended up with the 29/19 pair on the first gear position and a 29/18 set on the kickstart/4th gear end. This raises 1st, 2nd and 3rd bringing them closer to top and reduces the gap between 1st and 2nd and 3rd and top. So to what result?
It is noticeably better and at Darley Moor I ACTUALLY WON A RACE! Admittedly it was the over 50's handicap but I did finish ahead of a number of riders who had previously beaten me on many occasions.
The last meeting of the season was at Cadwell where I failed to improve on my 8th slot in the GB Motors 500cc Championship by falling off on the last bend on the last lap. No real damage done apart from severely dented pride especially as half my family had made a long journey from Suffolk to cheer me on.
Going quicker in 1998.
For the time being I will concentrate on the valve timing and compression to improve my chances in 1998.
Royal Enfield racing cams were produced but are extremely rare and difficult to recognise. They give faster and more lift but the actual opening and closing points are close to standard cams. Basically they reach and hold their full opening longer than standards. So if any of you out there have a pair get in touch. I may have some standard cams built up and reprofiled but the cost (over £100) has put me off for the time being.
I am hoping for a season without major engine failures and a bit more dicing in the middle of the pack - it's too much to expect to beat the G50's, Gold Stars and Manx Nortons especially as I am no Steve Linsdell. I will also be campaigning the Crusader for owner Steve Cotrell but that's another story…
1999 and 2000 to follow.
Technical Specification
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