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A7 & A10 Engine / Re: Pre ignition pre detonation
« Last post by Yeti on 18.10. 2021 20:22 »
I would say that you should be able to get timing pretty exact by using a razor/ a calibrated rod and a points buzzer
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Lifting boats tomorrow. I used to lift most of the boats from the two small nearby harbours at the beginning and end of each season, but gave it up around four years ago as I was finding it too physically demanding - yes, I do use a crane  *smile* but there's still plenty of physical involved. My son helps me now, but these days we only do my launch and a couple of others.
But the reason I'm posting is bike related - as my son's coming round I'm hoping we'll have enough time to run a short vid of my first vee twin (the one Chaterlea John recently enquired about). Just checked the oil, tyres etc in anticipation.
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Tis the way these Notruns be BS.
I wiped mine over the other day  . . .
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Rode the Norton to a Velo branch agm. Note the huge turn out of Velos. Rain, lots of spray on the Motorway, visor fogging up the biggest problem. Bike going well though, just dial in 75 and go, imagining the views which would have been there had it not been for the rain, spray and mist. I'm sure Stirling Castle will still be there for next time. 
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A7 & A10 Engine / Re: Pre ignition pre detonation
« Last post by RogerSB on 18.10. 2021 11:52 »
Thanks Julian.

Trevinoz no apology needed. I’m grateful for your input.

I’m fairly meticulous and I’ve been searching the info I have because I was sure I would have got 13/32" in my head from somewhere legit.  First check was the BSA Instruction Manual printed Aug 1971 and there it says 13/32”. Next checked the Haynes book published 1990 and there it says 11/32” but I’d pencilled 13/32” beside it at sometime.

I suppose an exact figure is a bit redundant these days with the different petrol and, as Julian pointed out, wear and tear. That’s why I wondered if there was a ball park figure members used based on todays petrol. So for a 1960 GF 11/32" - 13/32" Julian's info is good enough for me.

Rog.
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A7 & A10 Engine / Re: Pre ignition pre detonation
« Last post by JulianS on 18.10. 2021 10:53 »
Worth checking the ATD function if an engine pings, if the springs are tired it will go to full advance too soon and it will probably ping. On the other hand if the unit is sticky, maybe because of corrosion inside the unit it will advance too slowly.

If an engine gets hot and bothered and down on power it can be an indication of ignition being too retarded.

BSA altered the recommended ignition timing for all the A10s to 13/32 btdc in 1959 (previous 3/8 for Rocket and 11/32 for GF). That is in the service literature and the handbook, as RogerSB says.

It will remain a subject of debate, personal opinion and experience as to what the best figure is.

My own experience, bike currently iron head 7.25:1 pistons is that it runs fine on my approximation of 13/32 btdc and also on 11/32 btdc. So not too fussy.
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G'day Fellas.
I just sent Worty a PM and email.
Hope he answers.
Cheers
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Rode out to the Essex branch Guzzi Club meet up yesterday. This month it was near Battlesbridge, so not a great ride for me. I took Hardley.
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It's been 3 weeks since Wortluck told us he had covid.
Wonder how he is? Anyone heard?
cheers

He has not signed in for the last three weeks. *sad2*
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A7 & A10 Engine / Re: Pre ignition pre detonation
« Last post by groily on 18.10. 2021 08:04 »
The A10 engines pinged badly from new. I should say the high compression engines.
Couldn't agree more.
Alloy head SRs or any other HC motors friends have brought round over the years have always seemed to need retarding a bit, despite owners' occasional reluctance to depart from some magic number they've got in their head, read in a book or were told by some bloke 'who knows'.

To BoN's point about manual + ATD  . . .  can be done, has been done. Just set timing with ATD wedged open and camring at full advance, then you obviously have the best of both worlds in terms of adjustability to cope with heavy loads or 'big throttle low revs' situation.
But a few things to bear in mind: first, running with a manual cam retarded from its advance setting weakens the spark; and secondly, the chances of wear gradually interfering with the firing interval on manual cams is greater than on fixed ones. Not to mention AR cable arrangements that sometimes jam or self-detach at the cam and / or are impeded by fuel lines, carb fitments etc on some bikes. Also requires a cranked  HT pick-up at 45° on the cable side usually on As, and the quality of the available part is a bit so-so.

I have a mix of manual AR & ATDs myself (but no bike with both)and I prefer  fixed cams, once having got the firing interval to 180:180° across the rev range.
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