how hard are rocker shafts meant to be?

this one has done maybe 1500-2000km, and the end snapped off as you can see...



I took the rest of the shaft out tonight, and it's very soft - one pass over with a semi-circle file will make a mark the size of a tic-tac.

This topic on turbominis has the same, but from 2008 - http://www.turbominis.co.uk/forums//ind ... tid=238138

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did I tell you that I won a trophy?

I find the HD shafts from Karcraft are pretty hard.
Stock replacement shafts are soft, not hardened at all. Material unknown. But BMC ones were good steel, probably EN8 or better.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Any reason why they're drilled out to such a thin wall?

That looks more like a hardened shaft break, however this can happen in ductile steel (soft) if a load is applied very rapidly. Hardening a shaft is unlikely to alleviate this problem.

Could be rubbish steel too.

There's also a very recent thread about rocker shafts snapping on the Mk1 forum : http://mk1-forum.net

A recent HD shaft I got was very poorly drilled and countersunk compared to previous. IMO quality of these is becoming a problem.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.