Kawasaki KR-1S

Inspired to embark on a quick-win project? Kwak’s two-stroke is readily available, easy to work on and a hoot when finished. Here’s how to make sure you get something worth your time...

FAST BUT FINICKY

The KR-1S is fast – Performance Bikes recorded 139mph. But race-like speed means race-like fragility, and even new the KR-1SS was known for seizing. The lower peg ring let the ring spin and stick in a port, and some had wonky engines – the head is one piece but cylinders are separate, and not all were the same length. Inspect the oil pump too: the nylon gear loses teeth which jam it solid, also causing seizure, and you can only get secondhand ones these days. If you rebuild the engine, run it in with BR9 plugs before switching to the standard BR10ESS – this stops fouling and reduces the risk of holed pistons when you eventually get round to caning it.

TWO-STROKES STILL HAVE VALVES…

The parallel-twin 249cc two-stroke has powervalves on the exhaust port, to vary the timing and allow a mad 55bhp top-end without losing everything low down. You should hear the KIPS system checking itself when the ignition is turned on. Check the condition of linkages as they like to fall apart, and the valves can seize due to the build-up of carbon. If it’s all shot, don’t worry – replacement valves and linkages are available.

NICELY LUBED UP

Find a KR that’s been run on the finest semi-synthetic two-stroke oil. Some have had their oil injection system ditched to run premix (it should be 30:1), but for the road refit the oil system to reduce faff and chances of embarrassing forecourt spillage. Secondhand pumps and tanks are fairly easy to source.

DON’T FRET OVER ORIGINALITY

The standard aluminium silencers disassemble themselves inside and start to rattle – plenty were replaced back in the day under warranty. Predictably, original cans and expansion chambers are now hard to find, especially in good nick, so don’t be put off by a bike wearing aftermarket exhausts – Arrow, Jolly Moto and Jim Lomas are all common and all good. Be wary of a bike with scuffed and repaired Swarbricks or unbranded hand-made pipes – it may hint at a racing background.

GETTING IT SORTED

No good popping to the local main dealer. Most genuine parts are discontinued, and used spares are getting rare. However, Japanese bearing manufacturer Koyo can sort you out things like little-end bearings, and Mitaka make very decent aftermarket pistons. Their are pattern seals and bearings so that a specialist can rebuild the crank (which you’ll definitely be doing at some point), using remanufactured centre shafts and KMX125 con-rods.

CRACKING JOB

Bodywork was flimsy and cracked when new, and by now will be super-brittle. Look for damage near the fairing stays, under the pillion seat and by the mirrors. Expect a patchwork of repairs and aftermarket plastics and paint, though don’t be too put off – pristine original plastic parts are like rocking horse teeth these days.

‘Pristine plastics are like rocking horse teeth’

TYRED OUT

The KR’S 18-inch rear wheel restricts tyre choice. If you want proper sports rubber then Bridgestone’s old-butstill-good BT-090 is still the way to go. BT-92S are good for longevity over grip. Fitting a 17-inch wheel from a Suzuki RGV is a popular mod to allow greater tyre choice.