ORIENRAL ANGLES
It’s a poorly kept secret that my shed life revolves around one of the world’s most vilified power units – the humble two-stroke. Whether you love them or hate them is totally irrelevant – the fact remains that strokers unquestionably motivated a generation of riders that now comprise the classic bike movement.
Those that have ‘kept the faith’ now face numerous issues when running what’s colloquially referred to as stinkwheels. Without question the huge lure of strokers is the way in which they deliver their power, and this doesn’t automatically mean hoisting front wheels in the air etc. When a two-stroke ‘comes in pipe’ little else compares, be it an almighty kick up the derrière from a multi or a delicious dollop of torque from a single. The feeling is both intoxicating and addictive, which goes a long way to explain why there’s a veritable raft of companies supplying parts for machines that logically should have been recycled into white goods 30 years ago.
That we can still buy both running parts and service items is fantastic, but what never ceases to amaze is the breadth of reproduction parts available. Complete exhaust systems for Kawasaki triples, petrol tanks for Yamaha LCs, even complete crank and rod assemblies for air-cooled Yamaha twins are available, in stock, on the shelf. If you thought it was all just some quirky passing fad, know this – a high-end German company has invested heavily in the manufacture of quality pistons and rings and this kit is way beyond the original OEM quality. Running a two-stroke now is arguably no more fraught than it was back in the 1970s and, potentially, may be actually easier due in no small part to the use of modern electronics.
The lifeblood of any engine is its oil and never more so than with a two-stroke. The advances in lubricant technology have been phenomenal and pretty much any two-stroke oil from a well-known brand will suit 85% of machines. If you’re fortunate enough to own a liquid-cooled 1980s sports twin or four then fully synthetic is the only way to go; likewise if you run a heavily tuned air-cooled machine the top-spec oils are the ones to use. For the rest of us, either a modern mineral oil or a semi-synthetic will be more than up to the job. Many of the latter format were designed for use in modern twist-and-go scooters so if they can stop naive teenagers from perpetuating cold seizures upon their ‘peds’, semi will be more than up to the task on our old machines.
The one area where the past beats the present hands down is petrol – simply put, the stuff at the pumps isn’t designed for old bikes or anything that runs a carburettor. Its raison d’être is for modern fuel-injected engines that run lean burn technology, anti-knock sensors and a host of other gizmos. Until late 2019, many super green or 99 octane pump fuels were ethanol free – but not any more; it’s all E5 and we’re being threatened with E10 soon as well. Few of us can afford ethanol-free petrol for regular use so what options are there? Some claim that it’s viable to ‘wash’ the ethanol out of petrol but this is a tedious chore, leaves you with a lot of dubious waste materials to dispose of and is, effectively, unproven. Without doubt ethanol is removed but what else is being taken out of the fuel? Just because the end product apparently works doesn’t mean that it’s fit for purpose.
Those that understand two-strokes are now seriously concerned about detonation and flame propagation. Modern petrol burns hotter, and is significantly more prone to pre-ignition in older engines. The way ahead seems to centre around re-profiling cylinder heads and reducing compression ratios. Neither process is cheap or straightforward but they’ll keep our old stinkwheels out there, running decades after their manufacturers could ever have imagined.