Table of Contents
This is an old revision of the document!
REF: Tools - 135
For Finding Piston Top Dead Center (TDC)
You can use the TDC mark etched into your flywheel on 2003 and prior stock engines.
- 1957-2003 stock flywheels have their own TDC marks.
- 2004 and later (or 03 and prior engines with 04 and later Sportster / Buell crankshaft upgrades) will not have a TDC mark on the flywheel so you'll have to make your own TDC mark on these if you need one.
With the Head On:
Using a Straw
See also Finding TDC of the Piston in the REF section of the Sportsterpedia.
This will not allow you to find true TDC if that is your intentions.
However, true TDC is not always necessary to find depending on circumstance.
You can use a straw through the spark plug hole to measure when the piston is close to TDC with the rocker box on or off.
The straw is soft enough that you won't risk breaking anything if it gets squished between the piston and the head / valves.
See procedure and cautions for Finding TDC with a straw in the REF section of the Sportsterpedia.
| A straw in plug hole for finding TDC 1) |
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With the Head Off
Using a Dial Depth Gauge
| Loosen the thumbscrew to allow you to turn the face (with a slight drag) 2) | Place on a flat clean machined surface or a mirror, turn the face to read “zero”, lock the thumbscrew. 3) | Set the base edges on the flats of the deck and drop the center probe on the piston to measure 'differential' from zero while turning the engine to find TDC 4) |
 |  |  |
| Double check the reading before proceeding | Double check the reading before proceeding |
