Author Topic: B31 Inlet Valve Rocker - oil drillings  (Read 385 times)

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Heywayne

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B31 Inlet Valve Rocker - oil drillings
« on: 20 March, 2017, 15:48:54 »
This is my first posting so I hope I've followed the process correctly.

The inlet valve rocker on my 1955 BSA B31 only has one oil drilling hole at the push rod end but the exhaust valve rocker has two drillings, one at the push rod end and one at the valve end. 
I think the inlet rocker should have two oil drillings as well and maybe the hole at the valve end was missed in production some 60 odd years ago!!
Does anyone have a spare they can check or does someone know for sure?

The book Pt No. For the inlet valve rocker is 65-1102 (mine is stamped 65-1103) The book Pt No. For the exhaust valve rocker is 65-1100 (mine is stamped 65-1101).

Thanks Guys

Heywayne

MALCOLM.JOHNSON

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Re: B31 Inlet Valve Rocker - oil drillings
« Reply #1 on: 20 March, 2017, 20:05:13 »
I can tell you with fresh embarrassing certainty, that the inlet rocker arm has only one oil drilling and that is at the push rod end. I know this, as I only today finished rebuilding my B31 cylinder head after a valve nipped up in its guide a couple of weeks back - inlet valve it was too! After years of trouble free use, I looked at all components carefully for a reason and noticed exactly what you have done, that there is only one drilling on the inlet side. I am guessing that being an inlet, there will be a tendency to suck oil down past the guide anyway, whereas the exhaust will have the opposite effect and hence the need for a little more oil. Early BSA twins did not have pressure feed to the rockers at all - relying upon mist feed! What caused my inlet valve to nip up (no damage by the way) after so much trouble free use, I believe to be pilot error :-[. When I got the bike back home and stripped, after the breakdown, I noticed that the advance /retard lever was not near fully advanced and that the engine had overheated after several miles of hard riding. The spark plug and exhaust valve were nearly white. No - normally it may be, but in this particular case it was not due to a weak fuel mixture. Malcolm.

Heywayne

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Re: B31 Inlet Valve Rocker - oil drillings
« Reply #2 on: 20 March, 2017, 20:29:44 »
Your confession is my reassurance it seems. Glad there was no damage. I have only ever tested the bike a few times so I'm new to the idea of the manual A/R lever.  I have been rebuilding the top end, re-bore, new piston, valves and guides etc and when I noticed this difference I immediately suspected a hard pressed worker trying to complete his quota all those years ago and simply missing a drilling.  I should never have doubted the quality of a BSA!!!
I must make sure I remember your oversight when I begin the running in process next month as I most definitely do not want to make the same mistake.
Thank you for clearing that up for me.
Heywayne