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Messages - om15

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16
Singles / Re: B31 Cush Drive Nut
« on: 23 July, 2017, 16:03:39 »
It's not a left hand thread by any chance? 

If it is seized you could try heat, if you have good access use a socket rather than stilson's for better grip, heat the assembly using a hot air gun, (the sort electricians use to shrink plastic heat shrink) then shock the socket bar with a hammer. Applying heat to the nut expands it more than the threads it is screwed onto.

17
Which BSA do you ride? / Re: Hello, new arrival
« on: 23 July, 2017, 15:54:47 »
I bought the bike 5 years ago, it had just been overhauled, loads of teething problems, all of which introduced me to the bike, usual stuff, gear shift fell off in cruise, clutch failed because the little grub screw came out of the clutch operating rod, bits of electrical failures, spark plug threads were shot, took the head off for an insert repair and pleased to see the piston and bore in as new condition. Slowly tidied her up with little mods and improvements, now is an easy starter, I was thinking of uprating to 12 volts and electronic ignition, but she is running ok as she is.
I have had five Hinckley Triumphs, Trident 900, Bonneville ( 2), Adventurer, and now Street Twin.

18
Singles / Re: Compression Test
« on: 23 July, 2017, 12:10:41 »
My service notes give the C15 compression ration of 8:1, (the C15S is 10:1), no mention of acceptable psi measurement, however I found this on wiki

Quote
Measuring the compression pressure of an engine, with a pressure gauge connected to the spark plug opening, gives an indication of the engine's state and quality. There is, however, no formula to calculate compression ratio based on cylinder pressure.

If the nominal compression ratio of an engine is given, the pre-ignition cylinder pressure can be estimated using the following relationship:
p = p 0    CR  γ     {\displaystyle p=p_{0}\times {\text{CR}}^{\gamma }}  p=p_{0}\times {\text{CR}}^{\gamma }
where p 0      {\displaystyle p_{0}\;}  p_{0}\; is the cylinder pressure at bottom dead center which is usually at 1 atm, CR    {\displaystyle {\text{CR}}}  {\text{CR}} is the compression ratio, and γ    {\displaystyle \gamma \;}  \gamma \; is the specific heat ratio for the working fluid, which is about 1.4 for air, and 1.3 for methane-air mixture.

For example, if an engine running on gasoline has a compression ratio of 10:1, the cylinder pressure at top dead center is
p TDC   = 1  bar  10 1.4   = 25.1  bar    {\displaystyle p_{\text{TDC}}=1{\text{ bar}}\times 10^{1.4}=25.1{\text{ bar}}}  p_{\text{TDC}}=1{\text{ bar}}\times 10^{1.4}=25.1{\text{ bar}}
This figure, however, will also depend on cam (i.e. valve) timing. Generally, cylinder pressure for common automotive designs should at least equal 10 bar, or, roughly estimated in pounds per square inch (psi) as between 15 and 20 times the compression ratio, or in this case between 150 psi and 200 psi, depending on cam timing. Purpose-built racing engines, stationary engines etc. will return figures outside this range.


19
Which BSA do you ride? / Hello, new arrival
« on: 23 July, 2017, 11:48:39 »
Hi all,
just found your forum, I learnt to ride in 1971 on a C15, and have had this C15 for the last 5 years, bought it as a runner and just kept improving/mending as I went along.
My other bike is a Hinckley Triumph Street Twin, (is that the wrong thing to say on this forum?)

Here is my 1964 C15.

cheers om

20
Singles / Re: Internal Incontinece
« on: 23 July, 2017, 11:28:22 »
Here it is

21
Singles / Re: Internal Incontinece
« on: 23 July, 2017, 11:04:57 »
I had the same problem with my 1964 C15, I thought that I would do more harm than good by splitting the engine, so I bought a small brass gas tap with an internal bore of 3/16" and fitted directly below the oil tank in the feed line, when ever it is parked up I shut it off to prevent wet sumping.

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