It may comes as quite a shock for those not in the know, but in the average four stroke road machine around 75% of the power is produced by the workings of the head alone. That means that the slightest thing awry within the complex castings, cams and valves, can dramatically effect the end result, which, even if the bike is intended purely for commuting, will result in poor running and fuel consumption. Thankfully, one man has made it his mission to help us all in the pursuit of a healthy top end.
Len Patterson is the likeable Londoner behind The Cylinder Head Shop. With 31 years experience in the bike game; he started off as a mechanic working in a variety of motorcycle shops before making the big leap into self-employment in 1976. “I opened up High Gear motorcycles in Wimbledon in this year” Len recalled “ we services and repaired all makes and with great success too eventually expanding in 1981 when I opened the second shop in Streatham road, Mitcham. During this period I also started developing my own parts for selected models that had built in or common problems, including a hydraulic clutch operating mechanism for the Triumph engine.
“The decision to specialise in cylinder heads was a natural progression from repairing complete engines. Just about every job I undertook during the early 80’s required extensive work and parts were generally of a poor quality too, this was taking too much time to prove cost effective, so I investigated areas that I could specialise in. Initially, I looked into crank rebuilds and balancing, but there was already a well-established core or suppliers in that field, but no one was repairing cylinder heads. Using the skills I had learned over the previous years I found that I could repair just about any kind of disaster in the head area, even TIG welding exploded combustion chambers and re-machining them back to their original condition. Now I have all manner of engines arriving for work, from the smallest moped race engines, to some of the most exotic and complex engines ever built.”
From the outset Len has invested heavily in new technology, he bought his first French built Serdi machine as far back as 1989, and now uses a Serdi 100 and the latest Series 5 cutting machines, the latter the only one currently in the UK and is used for many of the smaller and more intricate jobs. “For a long time, certainly during most the 90s, I was the only motorcycle shop in the whole of Europe using such advanced machinery. When I first started out, Serdi had no experience with motorcycle parts, let alone classics ones, so we worked very closely together to get it right.
“The Serdi 100 that I use for most jobs is a versatile tool indeed, it can accommodate just about anything from the smaller motorcycle head to a Buick straight 8 if need be. The whole job is pneumatically operated allowing the cutting pilot to be guided in place on a cushion of air, before being locked perfectly in place to ensure accuracy in the cutting and boring process. With the component firmly in place on the machine bed, the old seats can be removed using a solid carbide pilot and the whole prepared for the new seat to be fitted. The head is then heated while the new valve insert is frozen to create the working clearance to allow it to be dropped into position. Once fully home and secure the seat face is then cut in three differing angles, only one of which will make up the contact area and form the actual gas tight seat face, while the remaining two angles allow a smoother gas flow as the valve opens. With the work inside the combustion chamber complete the entire gasket surface can be renewed too using a diamond tooled re-facing machine, this is used for simple skimming jobs too when the compression ratio needs raising.”
Unlike many a classic workshop, Lens place has the look and feel of something all together more modern, more akin to a hi-tech race shop, such is the cleanliness and tidiness. There isn’t the usual swarf on the floor and general parts lying around everywhere, rather there is organised and controlled workload that sees every job receive the sort of attention to detail that Len has become known for. Despite his extensive background in the motorcycle trade, a lot of Lens work these days is on exotic classic car engines “some engines are so rare they are verging on the extinct so any damage can prove disastrous for anyone trying to keep such a beast going competitively, luckily I can repair any kind of damage to a head and, in most cases, improve the design bringing the specifications up to more modern expectations.
A typical example of this “improvement during repair” thinking is with the Kawasaki Z series head, over time they crack between the spark plug hole and the nearest valve seat, but by welding the damaged combustion chamber and then re-machining it to the correct shape, a stronger seat can be fitted and a smaller diameter spark plug too, greatly reducing the possibility of this happening again. As an added bonus, in race engines the extra space gained by this can then be use to machine a second plughole to provide a twin spark set up which, in turn, increases low down torque by around 15%, a useful gain for little extra work and cost. Another service I offer is gas flowing, this can easily yield a huge increase in outright horsepower, once again for a relatively modest outlay although this kind of work is done entirely by hand, and can be time consuming.”
Len develops his own parts wherever possible too, and is currently refining his own design of valve guides and valves, his copper nickel alloy, Nucleus valves and guides, feature a radical internal rifling that helps retain oil and prevent excessive valve stem wear. He also offers vapour blasting in house too, the end result of this process being a far nicer and less destructive process than the more common bead or grit technique. Len offers a door-to-door collection and delivery service along with a free consultancy and design service making him the man to talk to regarding anything that’s happening in the business end of you four-stroke motor.
The Cylinder Head shop
