Sunday, 23 January 2011
Carbs, I have discovered, are often the first thing to wear out on an old engine. Slides, needles and main jets are all affected by the gas shuttling back and forth on tickover and at low revs. The result is crap fuel consumption and wooly low-speed running. There's also the problem of fuel residues building up during laid-up periods.
Under the filth this Keihin carb looked OK after 30,000 miles but the odd auxiliary slide lifter mechanism was seized. The bike ran like a pig, partly due to the lifter but mostly I suspect due to the inlet stub having a large crack.
Fed up with carb trouble on my ZZ-R I sent the Domi carb to Mike Davies at JRS in Swansea (www.jrs.uk.com, 01792 402458), who refurbishes mainly Keihin, Mikuni and Dell'Orto to what I consider to be the best standard in the UK. Japanese carbs are either unobtainable or very expensive, so worth taking care of. Mike's service was very good. He rang me to confirm he'd received the carb, told me what he was doing and estimated the final cost. When a pilot screw didn't shift he rang me to say the machining and spares (from Dave Silver) would be a bit more.
It came back clean, set to Honda's recommended values and with a superb fact sheet. Cost was £110.
The stripdown shot shows the strange auxiliary lifter, which uses a ramp on the throttle pulley to help lift the slide under sudden throttle openings.