Hitchcocks Forum

Hello All,
setting the timing by trying to get top dead centre then back 1/32 or whatever the correct amount given for the retarded setting is not very accurate the crank can move about 5 degrees without the piston moving when at TDC because the crank pin is moving across the top of its arc. I have checked this with a engine on the bench. Set once using a degree disc at full advance.

When you know the timing is spot on and engine is fully assembled, get a top
dead centre tool that screws into the spark plug hole and machine it, so that
when it is fully down it touches the piston at the correct firing point.
Then to check or re set ignition just bring piston up to touch it. A finger can
just feel it touching. and with a thin feeler or paper you can check or set the
timing.
This is good when on holiday and you get problems. I did it at the Manx and
within 5 minutes I knew my ignition was spot on. I have done this on the bench
with a degree disc to check if this method is good and found it a very accurate
method.

Or just put the a spacer on the centre part of the timing tool that is the correct advance figure. Reduce the TDC tool until it just touches piston at TDC then remove spacer and the tool should now project into cylinder the correct amount. Bring piston up to just touching and bingo it is in the correct position for setting the timing at full advance, BUT. This second option is only accurate if a vertical Spark plug hole is used. It needs an allowance for the angle of the plug hole in relation to piston movement, any one know how to work this out?
Have fun.
Mikey

If you pin the bob weights open or have an old mag the 1/2 to 9/16ths BTDC is easy to find and fairly precise as the piston is far enough down the hole to take out any potential for crank rock issues. My tuppence worth. S:)

I agree with Simon on this, it's only recently that I have heard of this business of setting the timing when retarded, the way I have always done it is on full advance, if you think about it the engine runs 99% of it's time on full advance so why set it when retarded?, in a perfect world where parts are made to a perfect tolerance and never wear this would be OK I guess, but parts wear and setting when retarded in most cases will not give a correct advance setting. incidentally when setting you should turn the engine back beyond the quoted figure and then bring it forward until correct.

Yes, timing at full advance is the way. Mr H sells a stepped washer so lock the advace weights to make it a bit easier.

Oh, and always time the ignition while moving the engine forwards otherwise the backlash in the timing gears throws you out.

"'er indoors" throws me out------------frequently !!!