Hutch’s workshop tips
This month, Hutch is tackling the same job as Oli – Morini timing belts. How do they differ?
As a kid I grew up under cars, my dad being a motor mechanic. I first saw a cam belt on a car engine (possibly a Cortina) when it had broken with the resultant carnage sometime in the mid to late-1970s and made my mind up then that they were not a ‘good thing’. Far too complex compared to the overhead valve (ohv) pushrod engines I was used to. Of course, I now understand the advantages of overhead cam engines and that design has moved on a little with cam belts, overhead cam (ohc) being the norm in car engines.
The belt solution for ohc drive has not become so popular in bike engines for some reason, although Ducati & Honda seem to use it to some success; the Honda STs being particularly long-lived without need for new cam belts. Timing/cam chains can have their own problems, from Harley to Honda!
We ended up with a 350 Morini sport in the shed (bike acquisition seeming to be a cosmic sort of thing), which was ideal for the short local blasts we could get in during the disturbance that was 2020. I can see why the little Morinis were considered such giant-killers compared to bigger bikes of their era, or today, on the small Norfolk Broads. Anyway, after the winter had come, that for the sake of safety, peace of mind and to avoid potential engine carnage, I felt I should renew the cam belt, the irony being that Morini’s have both a cam belt and (short) pushrods.
I got a print of the pertaining section of the scant manual from the internet, wishing for a Haynes for once. With the bike on the bench and the peripherals removed – offside footpeg, gear change assy, generator cover – I identified the belt size I needed from the letter B stamped on the pulley; as Morini cam belts are not tensioned, they have three sizes, A, B and C.
I ordered a replacement belt and once it arrived, I continued the disassembly removing the generator nut with a couple of ‘dug-dugs' of the nut runner (air gun
– Matt). Going through my collection of pullers and special tools I found an M27 X 1.25 puller to remove the generator.
Following the manual/print-out, the stator screws were loosened and stator removed, having first marked where it was positioned, followed by the circlip, spring and crank pulley belt guide. With all these parts removed, the timing marks were meant to be exposed, however, no timing mark on the crank pulley was to be seen. What there was, fortunately, was a yellow mark left from the last time the belt was changed. I remade the yellow timing marks with a white paint pen, reasoning that the bike had been running very well with this valve timing.
I would like to say the old belt slipped off the two pulleys and the new one pushed on in its place.
In reality, both new and old belts were very tight and required more than a little ‘working', particular care being taken with the new belt – with much thumb pressure and no metal tools being used so as not to nick the belt material; all this while keeping the cam and crank pulleys in place and lined up with their timing marks.
Once the new belt was in place with the timing marks still aligned, the engine was turned over a couple of times to allow the belt to seat and ensure the cam/valve timing was maintained.
All the previously removed components were then refitted as removed, with particular attention paid to the alternator stator being refitted in exactly the same position it was removed from using the marks made before removal.
Fortunately, once the motor was all back together, it started with a few prods of the (awkward to me) left foot kick-start.
No nasty tinkling noises ensued and the bike was back to thrashing about until it left us for sunnier climes.