Author Topic: "The Rule of Five"  (Read 593 times)

Online Rookie_V#60

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"The Rule of Five"
« on: 22.11. 2018 13:34 »
The thing is, when you adjust the clearance in a particular valve train you need to make sure the cam follower or tappet is on the base circle of the cam, or the clearance will be excessive. You do this by checking the clearance on both valves in a cylinder when that cylinder is at TDC. The thing is, wild valve timing or quietening ramps in the cam profile means you have to be accurate when positioning the engine.

After decoking my Ariel SQ4 I had to adjust the valve clearances.  And thanks to Simes "rule of nine" ( http://ariel-square-four.blogspot.com/2018/10/rule-of-nine.html ) this was more simple, more exact and the engine was much quieter. (https://www.a7a10.net/forum/index.php?topic=13293.345)

I have now looked at this process for my BSA A7 and found this must be similar. I adopted it and so found the "The Rule of Five"!

Have a look at this 4 Pictures at the Bottom - this camshaft it‘s a spare camshaft for my BSA A7:

Start with top Picture:
On the right hand side of the picture, you see the thread retaining the cam sprocket, and that first cam is the inlet cam for number one cylinder - notice it is pointing straight up and the valve will be fully open.

Move to the left hand end of the camshaft and we are looking at the last or fourth cam, the cam for the inlet valve on cylinder two . It's pointing straight down, which means the valve is fully closed and the tappet is on the base circle, so:

The rule of Five         1 + 4 = 5  and again  2 + 3= 5  and again  3 + 2= 5 and again   4 + 1= 5 

Surely one or the other already knew this but for me as an older newbie it was a new experience and helped me a lot.

Cheers Rudy
1923 James Model 12 500ccm v-twin
1926 Douglas EW 350ccm flat-twin
1936 Motosacoche 500ccm single
1948 BSA A7 Longstroke 500ccm parallel-twin
1955 Ariel Square Four MKII
1960 C1, 1967 C2, 1979 C3-gone!

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Re: "The Rule of Five"
« Reply #1 on: 22.11. 2018 14:07 »

 Yup- yo're all over it  *wink2*...and full marks for the maths *conf2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online Rookie_V#60

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Re: "The Rule of Five"
« Reply #2 on: 22.11. 2018 16:42 »
Yes Sir,
 I was already a mathematical genius in the dwarf School  *ex*
1923 James Model 12 500ccm v-twin
1926 Douglas EW 350ccm flat-twin
1936 Motosacoche 500ccm single
1948 BSA A7 Longstroke 500ccm parallel-twin
1955 Ariel Square Four MKII
1960 C1, 1967 C2, 1979 C3-gone!

Offline cyclobutch

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Re: "The Rule of Five"
« Reply #3 on: 22.11. 2018 16:47 »
Yeah - I think there is some kind of similar approach out in Nimbus land. I don't have the maths for it, so just run each one up to TDC on compression and go from there. The clearances on that are something like 28 thou anyway so it's all none to critical.
Various, including ...
'58 Iron Head Flash Bitza


Online Triton Thrasher

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Re: "The Rule of Five"
« Reply #4 on: 22.11. 2018 17:09 »
Who needs that!

One inlet valve fully open- check the clearance on the other inlet valve.

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Re: "The Rule of Five"
« Reply #5 on: 22.11. 2018 18:33 »
G'day Rudy.
I know all the books say TDC but I'm with TT on this. Valve timing is 180 cam degrees apart so if one valve is fully open the other is fully closed and on the base circle.
Cheers
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Offline kiwipom

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Re: "The Rule of Five"
« Reply #6 on: 22.11. 2018 20:55 »
hi guys, didn't quite get the prevalence but all info is useful at some time thanks for posting, cheers 
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Offline RDfella

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Re: "The Rule of Five"
« Reply #7 on: 23.11. 2018 10:45 »
Same with cars. Just work from opposite ends: when valve no 1 is down, adjust no 8. When 3 is down, adjust 6, etc.
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Re: "The Rule of Five"
« Reply #8 on: 23.11. 2018 12:48 »
i am off to the pub!!! RD fella surely that's the rule of 9 --- like when I've had one over the 8 today *eek* *beer* *countdown* *bash*

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Re: "The Rule of Five"
« Reply #9 on: 23.11. 2018 12:58 »
 
Quote
Same with cars. ..

 I discovered the other week that my pushrod Hilux has hydraulic lifters- gimme a break- I've only had it twenty years... *eek*

 The 'one down one up' aforesaid secret five  mathematical formulae doesn't work with the Gutzzi, being 90°V., but just as  easy to get each one fully open an bc spun the crank one full reG pollution... *conf2*.... red neuron *conf2*..... revolution *woo* *woo* *woo* ( asst the pub with new phone that doesn't know me yet)

 StRt again- we've done a full *crank revolution* from any valve full open, and do that four times... easy really- done it about six times since '92... *yeah*
 ** An Alien-key in the crank bolt works as a pointer  *woo* *woo* *woo* ( that little bugger is hard to catch)

  *beer*

 Bergs  rounded me up there.... but I'm ahead of him already  *beer* *beer*


Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline cyclobutch

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Re: "The Rule of Five"
« Reply #10 on: 23.11. 2018 13:48 »
Hmmm. My Sportster has hydraulic lifters. I do my Guzzis like all my other bikes - TDC on compression and then check both valve clearances at the same time. Life's been good to me so far ...
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'58 Iron Head Flash Bitza


Offline SimonHolyfield

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Re: "The Rule of Five"
« Reply #11 on: 25.11. 2018 07:46 »
My SQ4 has certainly been quieter since I used this approach, first learned on a Morris 1000.

Glad the blog post was useful!
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com