Best way to use timing disc

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G3L1946
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Best way to use timing disc

Post by G3L1946 »

Good evening to all,

I have re-installed my inlet and exhaust cams correctly ( well, the correct dots appeared to line up )
but I just want to check all is ACTUALLY correct. I have attached the timing disc and got to TDC ( on ignition stroke, both valves rods free ). Now, is there a ‘best method’ to check the valve timings?
Do I turn the engine forward or backwards to check degree of opening? Do I start from TDC and work round? Best way to identify correct point when to measure?
An idiots guide of the process would be most appreciated. I’ve tried a few times but get some questionable readings! I think I have just baffled myself!

1955 G3LS.

Regards,

Steve
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G3L1946
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Re: Best way to use timing disc

Post by G3L1946 »

Good morning all,

It appears I may have found a lacuna in the knowledge base relating to timing discs? I have searched the internet and other sources available but, as yet, have been unable to find any useful instructions. Not to be outdone, I will continue my research and talk to a few ‘gurus’ in the hope of finding out something useful. If successful, having already discussed this with the Editor of Jampot, I will put together an article for the magazine. Might take a while though!
Any useful advice in advancing this proposal would be most appreciated.

Cogito Ergo Sum.

Steve
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clive
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Re: Best way to use timing disc

Post by clive »

I bought my first timing disc aged 70 having been playing with engines since the age of 15. I used it to time the Norton engine in a G15....once and then sold the bike as it was too heavy and a pig to start. Never found it necessary to check that the factory got the valve timings correct on cams of my singles so i am not much help!
clive
if it ain't broke don't fix
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G3L1946
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Re: Best way to use timing disc

Post by G3L1946 »

Thanks anyway Clive. Using the disc to set ignition timing is pretty straightforward and well documented. My interest, in the valve timing use, was stirred by my ever desire to ‘double check’. Having read that some engines, over the years, had been fitted with incorrect cams or timing pinions made this desire more acute. I have set the valve timing by ‘ joining the dots’ ( having satisfied myself my cams and pinion were correct ) with reference to that excellent article by Ken De-Groome.
As I say, I’ll do some research and, if able, I will put a short piece together for the magazine.

Cheers,

Steve

Gogito Ergo Sum
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dave16mct
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Re: Best way to use timing disc

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Dave.
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G3L1946
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Re: Best way to use timing disc

Post by G3L1946 »

Thanks Dave,
Appears relatively easy with engine out of bike and on a bench. I did see this video but moved on as I was seeking information as to how to perform task with engine in situ. Access to being able to insert a dial gauge is the big issue as far as I can see. I’m obviously not able to do this with engine in situ. I think therein lies the clue. ‘Joining up the dots’ might be the only efficient/practical way to set up when engine is in the bike? A good, clear and informative video though.
Steve
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Re: Best way to use timing disc

Post by SPRIDDLER »

G3L1946 wrote: Sun Nov 27, 2022 11:59 am Access to being able to insert a dial gauge is the big issue as far as I can see.
TBH I think you may be over-thinking the extent of accuracy needed when checking the valve timing.
I've never bothered with (don't have) a dial gauge. Determining TDC with a stick has been sufficiently accurate to judge whether or not the cams are fitted correctly and opening and closing at the specified times. With a timing disc and close observation any discrepancy is pretty obvious.
'There is a tide in the affairs of men
Which taken at the flood............'
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G3L1946
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Re: Best way to use timing disc

Post by G3L1946 »

You’re probably right. As I say, I’ve set the valve timing by aligning the dots as per the instruction manual. If was good enough in 1955 it’ll be near enough today.
Steve
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