TDC indicator

[Devlin]

I am trying to get one of the above  through the plug hole jobs  but jeez whats the deal with ebay almost all results are USA and all over the EU despite resetting my ebay preferences it still ignores the UK, down to paid placements apparently so shoves the small retailer right out the results  ,so if anyone knows where I can get on let me know
Devlin

[jhg1958]

From SRM £10.31 with a timing disc.

I used a pencil but then I am a cheapskate   
John

[Devlin]

I took apart a spark plug with the idea of making my own but I couldn't find something to slide inside without wobbling as the diameter is only the right size right at the bottom 

[Greybeard]

Better to put something straight down the hole rather than at the angle of the plughole. A piece of stiff wire or even a pencil is OK. Rotate the engine until piston is at TDC. Mark your pencil and the cylinder head. Mark your pencil at the given distance above the TDC mark. Turn the engine back then turn it forward* until the BTDC mark aligns with the mark on the cylinder head.
The advance/retard unit needs to be wedged fully open.

THIS IS IMPORTANT: Clean and adjust the points BEFORE you set the timing. This is because points gap affects ignition timing.

* I found it best to have the back wheel off the ground, both spark plugs out and the engine in 4th

[muskrat]

G'day Devlin.
Now that you've got a plug with the guts punched out you can make a piston stop set at the right height. Tap the plug out to 3/8 cei. Screw a bolt/stud into it.
Once I got my timing perfect I wound it over till the fag paper let go. I screw the plug in (washer removed) then screw the bolt/screw in (with loctite) till it touches the piston. From then on just wind the piston up GENTLY till it touches. Job done.
Cheers
s: most I find on ebay are UK https://tinyurl.com/akzzbz5p

[CheeserBeezer]

I use a gadget I made up myself. I bought a plastic ruler which I slimmed down so it would fit down the plug hole but left the top part wider so it wouldn't fall all the way in. I cut the last section off a magnetic telescopic probe and bent it so that I can count the ruler graduations as it slides past. the magnetic telescopic thing is very stable, being magnetic, and the ruler is slim so it fits down the plug hole vertically, not at an angle. Works a treat. For iron heads the magnet sits on the top fin, for alloy heads it sits on the head bolt nearest the plug hole.

[BSA_54A10]

Piston stop method is so much better than moving indicator
Rotate clocksise till pistonhits the stop & note the disc reading the do the opposite & split the difference for true tdc

[muskrat]

Piston stop method is so much better than moving indicator
Rotate clocksise till pistonhits the stop & note the disc reading the do the opposite & split the difference for true tdc

G'day Trevor.
I have a longer one to do that but you need a degree wheel. I do, most don't.
Cheers

[CheeserBeezer]

Piston stop method is so much better than moving indicator
Rotate clocksise till pistonhits the stop & note the disc reading the do the opposite & split the difference for true tdc

...agreed, my tool is for finding pre t.d.c. Timing disc and stop-bolt is more accurate for finding t.d.c. Timing disc also more accurate for finding pre t.d.c. provided a dial gauge has been used during the building process to identify correct pre t.d.c. degrees relative to piston height. The thing I made is in my 'side of the road' kit.

[Devlin]

Thanks all, I have decided the degree disc and piston stop methos is the way I want to go, my 1st thought was to use the dynamo drive but it goes ACW so not directly onto the crank I assume, so is it the other side with the cush device
Dev 

[RichardL]

Just for showing yet another method, and not debating with CB regarding a full stop device (I've never tried that and don't know what I'm missing). I use a homemade indicating stick as shown in the link below. It is stabilized similar to CB's and I read TDC when the tube stops to reverse direction, then, BTDC in 1/32" from the graticule.

https://www.a7a10.net/forum/index.php?topic=368.msg99758#msg99758

Richard L.

[Swarfcut]

 Degree discs  and precision piston stops along with high falutin' trigonometric calculations to compensate for the angle of inclination of a stick down the hole are all fine and dandy.......but

 Published data was for back then when fuels were different and engines were new. So even timed  up with ultimate precision to published settings, the only true test is how it performs on the road. These days a stick down the hole will be near enough to get a runner. If it turns out to be a clanker, advancing the timing will make it sound worse. If you are happy with how it runs, then by all means experiment for the best performance.

 Stick down the hole was the backyard traditional way, good enough for all but the ultimate power seekers.

 Swarfy.

[philwhitelaw]

If possible turn down a piece of bar with a spark plug threaded end and a (say) 9mm hole running through it to substitute the plug.  Take an 8mm fully threaded bolt of suitable length and round off the end of the shank.  Slide an electrical terminal under the bolt head and secure with a nut.  Place an insulating fibre washer under the nut and then Insulate the shank with heatshrink or similar so that 1, the fibre washer is held in place, 2, the bolt is still free to slide inside the bar and 3, the tip of the bolt is exposed.  Put the bar into the cylinder head and insert the bolt.  Ensure the bolt is free to slide up and down as it contacts the piston. Connect an electrical multi meter to the leccy terminal and an earth point on the engine.  Attach the timing disc as usual.  With light finger pressure on the bolt head, rotate the engine until the piston contacts the rounded shank in the cylinder.  The multimeter will give off a continuous beep as the circuit is made.  Note the before TDC figure.  Keep rotating the engine (bolt extends out and then back in) until the beeping stops (piston no longer in contact with the bolt).  Note the after TDC figure.  Halve the difference and turn the disc one way or the other by that amount.  After a couple of goes you should narrow down the position of the timing disc so that the beep starts and stops at the same number of degrees either side of TDC.  It is possible to get that piston to TDC exactly or at least to within half a degree.

[a10 gf]

ref. tdc \ timing... :O)

https://www.a7a10.net/forum/index.php?topic=368.msg10533#msg10533

https://www.a7a10.net/forum/index.php?topic=368.msg10538#msg10538

[Rex]

Recently I set up the valve and ignition timing on my Venom up on the bike lift and with the tank and dynamo covers off (to take the degree disc).
Got it all pretty much spot on too, then took it for a ride and the ignition timing (ATD) slipped.
Rather than go through the rigmarole again I did the pencil down the plug 'ole trick (11mm BTDC in this instance) and it works just as well as before.
It is possible to over-complicate maintaining  these old bikes..