As it's not possible to directly find TDC, we calculate the position.
For this you need a protracter ( degree disk ), a DTI ( Dial Test Indicator ) and some sort of pointer.
If you donīt have any degree disk you can download one here Pic here
Print and glue to a cardboard paper, plastic disk or metal disk. Make the center hole 16 mm
If you donīt have any DTI you can make a tool for this by using an old sparkplug. Clear the inside guts and make some threads for a bolt. Pic here
Beware when you hit the piston with the bolt!!!
Fit a protracter ( degree disk ) to the end of the crank. Mount your degree wheel with the TDC mark where you think you have the TDC
so you donīt have to move the degree wheel that much later. Better to just adjust the pointer.
Attach a pointer that can be moved for calibration.
If you donīt have any pointer,you can make one easy. Sample here
Using a DTI ( Dial Test Indicator ) on top of the piston, first measure a point before TDC.
This point could be a decision of your own.
Make a note of this in cell A .
(No need to have 2 DTI.)
Then at that piston postion, read the number of degress on the disc and make a note of that in the " before TDC" cell B .
Rotate the crankshaft backwards and find the same piston position coming up the other way to your measure point (A ).
Ie: you should read one number before TDC and one number after TDC.
Read the degrees at that point, make a note of that in the " after TDC" cell C .
Now move your crank backwards to this degree ( cell D ) If the number is negative the degree should be after the TDC on the disc.
If the number is possitive the degree should be before TDC on the disc.
Then adjust your pointer to zero,TDC is indicated.
Ie: TDC is between A and B .
Then do it all again just to prove nothing slipped. Keep repeating till you get it right.