Author Topic: Finding TDC  (Read 9483 times)

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mattjohnson207

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Reply #45 on: November 16, 2016, 02:10:44 am
had the same backward sprag slam hot start issues before i tore it down  and sent it to Ace.   work issues prevent me from finishing the project at this time...but thank you all for your input     


Karl Fenn

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Reply #46 on: February 28, 2021, 01:20:41 am
Those engines are a pain to find TDC you think there would be some markings to assitain accurate TDC one old school way is to use an upside down knitting needle then make a mark when engine reaches TDC then run it round again, or better you might be able to use a dial gauge which would be the most accurate after taking a few readings, TDC is a must for obtaining valve and cam timing, very important in relation to ignition timing BMW use a lock pin on singles to obtain spot on TDC which is dead essential for cam timing. There probably is a better way not yet discovered but the knitting needle will work albeit not being exact spot on.


Karl Fenn

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Reply #47 on: February 28, 2021, 01:37:58 am
I doubt the French chalk on the tire would be accurate you must remember there is considerable backlash in the chain and sprockets and the gearbox it may be accurate enough but l would wager a few degrees out, in reality the engine design comes from the dark ages they did not have modern timing marks back then but in saying that with mordern gauges you can obtain them, let's not forget this design goes back 70 years.


tooseevee

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Reply #48 on: February 28, 2021, 11:51:45 am
...... one old school way is to use an upside down knitting needle then make a mark when engine reaches TDC then run it round again,


           Or use a short piece of small diameter wooden dowel.
'08 Black AVL Classic.ACEhead 9.8:1/manifold/canister. TM32/Open short bottle/hot tube removed. Pertronix Coil. Fed mandates removed. Gr.TCI. Bobber seat. Battery in right side case. Decomp&all doodads removed. '30s Lucas taillight/7" visored headlight. Much blackout & wire/electrical upgrades


Karl Fenn

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Reply #49 on: February 28, 2021, 03:11:49 pm
I have done some research on these models from original factory workshop manuals, it seem the only accurate way to find TDC is by attaching dial gauge via spark plug hole, for ignition timing rotate the crank and set the gauge to 0.8 mm BTDC then adjust the back plate, it sounds odd l now no degrees but this is the procedure listed in the archives for general publication, there appears to be no timing marks on engine other than cam dots which are set after you establish TDC, valves are also set at the TDC compression stroke both valves closed.


Bullet Whisperer

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Reply #50 on: February 28, 2021, 03:37:35 pm
I have done some research on these models from original factory workshop manuals, it seem the only accurate way to find TDC is by attaching dial gauge via spark plug hole, for ignition timing rotate the crank and set the gauge to 0.8 mm BTDC then adjust the back plate, it sounds odd l now no degrees but this is the procedure listed in the archives for general publication, there appears to be no timing marks on engine other than cam dots which are set after you establish TDC, valves are also set at the TDC compression stroke both valves closed.
When doing your research on these models, did it not occur to you that there is no back plate to adjust on these [AVL] models?
 B.W.


tooseevee

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Reply #51 on: March 01, 2021, 11:41:00 am
I have done some research on these models from original factory workshop manuals, it seem the only accurate way to find TDC is by attaching dial gauge via spark plug hole, for ignition timing rotate the crank and set the gauge to 0.8 mm BTDC then adjust the back plate, it sounds odd l now no degrees but this is the procedure listed in the archives for general publication, there appears to be no timing marks on engine other than cam dots which are set after you establish TDC, valves are also set at the TDC compression stroke both valves closed.

         We're talking AVLs here. AVLs are Electronic Ignition and have no points backing plate to adjust.

          Finding TDC center on my AVL to Set The Valves takes about two minutes with the "timing mark" on my little piece of dowel. The hardest part is rotating the rear tire and keeping my eye on the mark. Everything hurts especially working on the ground.

          I know. I know. Harbor Freight Bike Lift. I'm an idiot  ??? ??? :) :)

          Another hint: Remove the tappet cover center post when setting valves. Gives way more freedom for the wrenches.
'08 Black AVL Classic.ACEhead 9.8:1/manifold/canister. TM32/Open short bottle/hot tube removed. Pertronix Coil. Fed mandates removed. Gr.TCI. Bobber seat. Battery in right side case. Decomp&all doodads removed. '30s Lucas taillight/7" visored headlight. Much blackout & wire/electrical upgrades


tooseevee

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Reply #52 on: March 01, 2021, 11:42:41 am
When doing your research on these models, did it not occur to you that there is no back plate to adjust on these [AVL] models?
 B.W.

        Woops. Shudda read this posting first before I answered Karl.
'08 Black AVL Classic.ACEhead 9.8:1/manifold/canister. TM32/Open short bottle/hot tube removed. Pertronix Coil. Fed mandates removed. Gr.TCI. Bobber seat. Battery in right side case. Decomp&all doodads removed. '30s Lucas taillight/7" visored headlight. Much blackout & wire/electrical upgrades


Karl Fenn

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Reply #53 on: April 05, 2021, 02:19:18 pm
A TDC guage £30 on eBay.


hpwaco

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Reply #54 on: April 07, 2021, 02:31:47 am
Anybody mention that Hitchcocks sells a TDC "tool"?  I broke the porcelain off an old spark plug and use a wooden dowel thru it.


Karl Fenn

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Reply #55 on: April 10, 2021, 09:47:11 pm
Yes l have one of those old 70s plug type gauges as well, but l have to say they are not the most accurate, but in saying that traveling through memory l have once used a knitting needle cut down.