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[Leon Novello]

Check for a cracked piston. Common in Australia.

[Gwilly]

Catastrophic sequence in the blink of an eye... Piston crown seizes at the start of the downward power stroke, flywheel inertia plus bike momentum/weight rips the piston apart at the weakest point, just under the oil ring land, leaving the flywheels and con rod to continue on there unfettered way.. Around and back up the bore..

Meanwhile the exhaust valve starts to open and maybe hits the piston top still seized in the bore, not long after the sledge hammer of a con rod tries to reconnect the two piston halves, blasting the exhaust valve and push rod, maybe damaging the rocker fixings and cam surface.. Con rod has to go somewhere so goes through the piston twisting as it goes. Tremendous forces at play.. It was at this point that the con rod snapped on my BSA and the next rotation saw the half conrod exit through the crankcase..

Its that deathly silence that gets you as you come to a halt.. Mine was piston too tight in rebore and maybe running weak and hot..

Nothing to do with racing my mates Morris 1000 with the Riley 1.5 twin carbed engine in..

[zippy]

Think I'll just leave my Bullet in the shed...... :/

[Norm]

Very wise move zippy just polish it and you will have no fear

[zippy]

While were on the subject of major engine disasters.... Anyone got a better idea for getting the timing side roller bearing outer race out of the left hand casing? Until this is done, nothing else can be removed. Heating and tapping hasn't worked on any of them. - they are TIGHT! I've tried various pullers and levers, even one of those expanding blind bearing pullers, but there is nothing for it to get hold of - as there is a spacer tight up behind it between the roller and the ball bearing circlip.The roller race is pretty much smooth - so no joy there.... Only thing that has worked so far is grinding 2 grooves in the surface with a Dremel and tapping a section out, collapsing the race. - But this is far from Ideal, as it is risky for the crankcase, drops hardened dust into the ballbearing below and takes far too long...

[Norm]

Very easy zippy, screwdriver and break the cage, rollers fall out, run a bead of weld around the inside of the outer bearing cage, wait for it to cool and the bearing falls out. Heating the case up sometimes works but the weld trick is quick and easy

[zippy]

Thanks Norm, Will try that! - seems counter intuitive tho - as you would expect the bearing to expand more than the case and grip tighter...I think all my roller bearings have been well worn - as I didn't need the screwdriver to break the cage. the rollers, cage and inner race more or less fell out as 1 piece !

[Leon Novello]

Spare piston, don`t leave home without it. Changing one on the roadside in Central Australia.

[simon]

That is sad news.

[Norm]

Zippy with welding the bearing as it cools it shrinks