After the Southern Oddyssey both bikes were due a bit of a birthday. First up, an oil change along with a general going-over.
As previously reported my drive belt was well overdue replacement. The manual says 12,000km and by this time mine had done 26,000km and measured a uniform 24mm wide. A new belt is 25mm wide and the manual specifies a minimum width of 23.5mm. So whilst my belt was still within tolerance and showed no sign of cracking, chafing, delaminating or whatever it had worn enough to cause a significant increase in revs at cruising speed and so had to go.
To replace the belt one needs to remove both the front and rear pulley. Both require a tool to hold the pulley assemblies still while the hub nuts are undone so I fabricated one of those out of a bit of mild steel strap - if anybody needs further details let me know and I will send a picture.
The front hub incorporates the centrifugal weights so I opened this, cleaned out the dust, checked the weights for round and found them well. Out of curiousity I weighed them and found them to be 22gm each as opposed to the 17gm which the workshop manual specifies - obviously the manual doesn't necessarily reflect what we get on the Kiwi market.
The rear pulley incorporates the centrifugal clutch which had built up plenty of dust from the linings and belt so again a thorough blow out was in order. After 26,000km the clutch linings showed little wear.
Visual inspection of both assemblies found no problems and so the new belt was fitted. This is a very simple and self-evident operation, as is reassembly using the aforementioned holding tool and a torque wrench. Both front and rear pulleys must come at least part way off their shafts to enable the belt to come off - there isn't enough clearance between the outer edges of the pulleys and the transmission casing to change the belt with the pulleys in situ.
Next came valve clearances. At 26,000km my bike was becoming progressively more reluctant to start when cold but not when hot which is often a symptom of valve clearances having closed up This proved to be the case. Both inlet valves had closed to no measurable clearance while the exhaust valves were both at the standard .15mm clearance. Adjustment is by screw and locknut except that the "screw" is in fact a small square headed bolt. The square head looked to be about the same size as the square drive bit used to do up wood screws so I tried a wood screw for size and sure enough it fitted the head of the adjuster bolt. So simply by bending a long wood screw to right angles I had a crude but effective tool to hold the adjusting bolt whilst tightening the lock nut. With the inlet valves set to the appropriate .1mm clearance the bike now starts and idles properly from cold. It also develops noticeably more power, reaching about 88km/hr up the Ohope Hill vs about 82km/hr before adjustment.
Access to the valves is quite reasonable with the seat unit removed along with the plastic trims above and below the footwells.
At 8,000km the valve clearances on Jocelyn's bike were correct.
The spark plug gap in my bike had opened out to about 40 thou so I brought this back to 25 thou. Modern spark plugs are amazingly reliable devices given the job they perform. That the standard NGK fitted to the SYM has fired reliably for 26,000km speaks volumes for their quality. I have memories of the crap which masqueraded as spark plugs back in the '60s (the first NZ made Champions come to mind) which needed replacement about once a week in the small two stroke engine which "powered" me around the streets of Christchurch in those days. Compare this to the iridium plugs in a Mitsubishi that we had which were absolutely fine after 188,000km when we sold the car. I am a bit of an optimist, believing that if there is only one of anything to keep an engine running then it probably will fail so both bikes will shortly be fitted with nice iridium plugs. They're relatively expensive at about $35 each, but this is cheap in comparison to the cost of getting stranded somewhere.
Finally, when talking about mileage I called in to a scooter shop in Christchurch to have a look at a Kymco 500 and while there a guy mentioned a SYM 250 being used by a rural postie down Invercargill way which he understood to have covered around 80,000km so far without problems.
Finally, new tyres for the rear of both bikes. I searched fruitlessly for something a bit higher profile than the standard 130/70 so standard it is, this time IRCs. One is Japanese, the other made in Thailand. Both required more scrubbing in than most tyres, but now that they are scrubbed they seem to handle well so we will see how they last.
Cheers
Flange
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