TDC the measuring of.

[eden]

If the stroke and rod length is known then the piston travel distance can be calculated for a given degree setting. EG for a 58mm stroke/107 rod at 19 degrees BTDC the piston will be 1.9973mm down the bore. Simple trigonometry!

I use the dial gauge to find tdc then use the equation to then find and mark my timing marks on the mag, using the dial gauge to get the MM before tdc.

[Dimitrios_231]

Original workshop tool

[Dimitrios_231]

Original 60s TDC tool left,
modern TDC piston stop right,
both plug at the spark plug hole.

[eden]

Original workshop tool

they would need "fettling" for use with big bores

[Dimitrios_231]

I understand what you mean,
I have done a good cast iron 70mm one,
this bracket is a remade for 200cc crankcases,it maxes out at 68mm

[Strummer10]

Guys 1/ where's the best place to buy a dial gauge ? and 2/ Where is the best position to determine TDC in your opinion ? Is it when it first arrives at TDC or after the dwell period just before it then starts to go back down the barrel ?

[Muppet]

Guys 1/ where's the best place to buy a dial gauge ? and 2/ Where is the best position to determine TDC in your opinion ? Is it when it first arrives at TDC or after the dwell period just before it then starts to go back down the barrel ?

mid dwell

[Strummer10]

THanks Muppet........Guys what's the best dial gauge to buy and from where ?

[rosscla]

MB do it as a set,

Or shop round on eBay

[Muppet]

analogue metric dial 10mm travel in 0.01mm increments; ebay is your friend