Just wanted to get a fiew ideas on this because I have noticed once you get to TDC their is about 10 degrees of movement left and right before the piston moves off of TDC[sm=confused.gif]

The movement is on either side of TDC.. you are at the top of an arc but because its an arc and not linear you have movement on each side. Its the mid position between the left and right free movement. Hope this helps. BobH.

Place a mark on the crankcase in a spot that's easy to see. Move the piston to TDC (roughly), now move the crank until the piston JUST starts to move down. Now make a mark on the crank even with the mark on the case. Now move the crank the other way and do the same thing. Find the mid point between the two marks and you have as true a TDC as your going to get. If you have a dial indicator you can get a little better reading.

What I used to do on my cars when I used to race....

You need a degree wheel attached to the crank, a dial indicator long enough to reac the top of the piston through the plug hole and a watchful eye on the indicator and the degree wheel.

Once you are set up, crank the engine over and watch the dial indicator. When the indicator STOPS moving, look at the degree wheel and note the measurement. Now continue turning the engine over in the SAME direction. You will notice that the indicator will not move for several degrees on the wheel. Once the indicator shows movement again, Read the degree wheel again. Now take the two readings from the degree wheel and subtract them from one another, then divide by 2........take this number and ADD it to the lower of the 2 readings from the degree wheel.......This total gives you the EXACT loation of TDC.......

Note that it is important to NOT move the degree wheel in relation to the crank during this process.

So actuall TDC is in the center of the movement left and right before the piston moves off of TDC? Thanks

YUP

The most accurate way to find TDC is to use a piston stop (a bolt screwed into the spark plug hole that stops the piston about half way in the cylinder). Use a degree wheel and pointer. Turn the crank gently one way and then the other. Right in the middle is BDC. 180 degrees away on the degree wheel is TDC. The piston hardly moves at all near TDC, so that's why the piston stop is more accurate.

Here's what i did, bought this tool for 15.00 and made a sleeve for it to slide into then screwed it into the clyinder head. and rotated the piston till i found T.D.C. WA LA. T.D.C

Tim

Once again the voice of time honored practices...

I agree with Diablo, this is the most accurate method available for locating TDC, bar none IMO. And you don't need any goodies or measuring devices.

If you need to do this most likely your checking and or setting the timing. Thus the need for a degree wheel. C&H Ignition has a down loadable degree wheel on their site together with instructions which apply to many engines and ignition systems.

The stop can be manufactured from an old sparkplug by removing the electrode and porcelain and tapping it for the appropriate bolt. In some cases you can simply find the correct thread type/size. Some are 14mm...

Why not just take the back crankcase cover off and turn the crank intil the crankpin is at its top. Then mark the prop drive washers position on the crankcase.

Cheap instant piston stop Champion RN14YC or RNxxYC. 14mm long reach.
For a few bucks H-9 sells one made by Zenoah