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Messages - STAR TWIN

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Oh dear, that shouldn't happen. As chair of our local VMCC section, I always make a point of welcoming new faces - and there's usually one or more members chatting to them already. Perhaps South Derbyshire needs to take a look at itself.
Why VMCC? No BSAOC branches up here in the frozen North.
In the dim and distant past, I did ask if I could attend a BSAOC rally on a Norton and got a very frosty response. It did put me off.

Singles / Re: Torque wrench
« on: 24 August, 2017, 13:47:31 »
It's fair to assume torque figures are for dry threads. B31 or unit single? These days it's an age thing... More and more people are looking for lighter bikes like C15s and cubs (both Triumph and Honda). Hopefully I'll be riding my heavyweights for a good while longer yet!

Singles / Re: Torque wrench
« on: 24 August, 2017, 06:15:35 »
Succinctly put. For big end bolts, accurate measure of bolt stretch is more accurate than torque figures. You just need the appropriate micrometer and the stretch figures - not always available!

Singles / Re: Torque wrench
« on: 23 August, 2017, 22:08:31 »
I do have a torque wrench but very rarely use it. If you have an engineering background, you should be more than capable of avoiding under/over torquing nuts etc. It's just the really essential nuts and bolts - con rod big ends for instance - that can benefit from the use of a torque wrench. And as you will know, you have to allow for clean thread vs lubricated thread and so on.
A good set of Whitworth spanners and 3/8" drive sockets is a good start.

Twins / Re: Rich running Super Rocket
« on: 17 August, 2017, 14:13:46 »
There is some confusion in the published figures. In my experience, a 420 is way too big. My one runs a 300 main jet. If you look at the figures for a 1960 Super Rocket, it states a 290 whereas a 1960 RGS shows a 420. Confusing, huh?

Singles / Re: BSA B33 sticky exhaust valve advise please
« on: 14 August, 2017, 22:42:03 »
I had a similar problem with a guide fitted to an iron head A7. What I did was to buy a set of engineers drill bits from Screwfix. I selected one that was a neat sliding fit in the valve guide. I then selected the next one up and carefully ran it through the guide. Problem solved.

The Star and Garter / Re: B31 Valve seats - lead free
« on: 14 August, 2017, 07:02:54 »
I run a B31, an A7 and various old iron-head Land Rovers. They all do just fine. I invariably use super unleaded petrol, but that's just to minimise the effect of ethanol.
When all this started, the SVVF (I think) commissioned tests on valve seat recession. None occurred below 3,500 rpm. Do you cruise your B31 well above this?
I would suggest putting any paranoia in a quiet corner and not disturbing it.

Which BSA do you ride? / Re: A7 Star Twin
« on: 11 August, 2017, 21:12:49 »
Glad you liked the picture Steve. These machines are used as ordinary transport and the longer distance the better. One son has made off with my copy Where BSAs Dare. If he's inspired, there will be a fight - the other son intends to inherit the Star Twin. Not 
 that I am in any rush to depart this mortal coil! Gordon.

Which BSA do you ride? / Re: A7 Star Twin
« on: 11 August, 2017, 10:23:58 »
And the Star Twin shares the shed with my wife's A10.

Twins / Re: BTH magneto fitted to my A10
« on: 10 August, 2017, 21:51:45 »
Proof of the pudding - or should that be K2F?

Twins / Re: BTH magneto fitted to my A10
« on: 08 August, 2017, 22:20:44 »
And yet and yet... My BSAs have had excellent service and continue to do so from their K2Fs. Both were rebuilt over 30 years ago and are going strong. I'm off for a 300+ mile trip on the A10 tomorrow with a ferry to catch. Wouldn't do that if I didn't have confidence in the magneto - or the rest of the bike.

Singles / Re: B31 Cush Drive Nut
« on: 23 July, 2017, 22:28:06 »
I don't think a hot air gun will be up to the  task. You may need a propane/butane gas torch and get the nut good and hot. If it's hot enough for oil to sizzle out of the threads a good clout with a hammer and a drift should shift it.

Singles / Re: Compression Test
« on: 23 July, 2017, 14:09:42 »
Simplifying... Atmospheric pressure is approx 14.7 psi. So 8:1 compression gives 14.7 x 8 = 117.6 psi. However, the inlet valve closes after bdc so you have to reduce that by a factor depending on the cam. For rule of thumb, the expected reading would be approx 90% lower. so 117.6 x 90% = 106 psi. All assuming perfect ring and valve sealing. Pretty close to what you have recorded.   

Twins / Re: Exhaust pipes
« on: 15 July, 2017, 06:23:59 »
With a normal setup I don't think it will make any difference. For information on optimal exhaust lengths, read Tuning for Speed. Only applies to unsilenced exhausts though. For the curious, a Velocette goes better with a fishtail silencer than without.

Singles / Re: Trial run
« on: 13 July, 2017, 16:56:00 »
Backfiring on the over-run when hot is frequently air getting into the exhaust where the pipe enters the cylinder head. Exhaust paste or even RTV should sort it.

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