Quadcammer

I have a used mantissport underdrive for a good price if anyone wants it

91K-Man

Just a Note, The original MantisSport prototype under drive pulley is still in use from 2006. Approx 20,000 miles of racing on it. No failures reported.

Jon Schepps

The RSS underdrive pulley I have (installed by previous owner) does not have a locator hole to pin TDC (no room for it due to smaller diameter), nor any TDC alignment markings on the rim. How does one find TDC once these pulleys are installed?

Quadcammer

I spose you could do some geometry with the stock pulley and its keyway vs. the locating pin and transfer that to the new pulley, but the easier version is probably just to reinstall the stock pulley temporarily or use the old stick in the spark plug hole trick.

5CHN3LL

If you removed too much boss and now find yourself needing to use the TDC pin, it wouldn't be much of a project to temporarily restore the boss with JB Stick Weld or one of they hobbyist low-melting-temp plastics so it will work with the stock (temporarily reinstalled) pulley.

You can grind or snap off the newly-added boss material after the repair is complete so you can reinstall the UD pulley.

Jon Schepps

I was hoping there was a TDC indicator somewhere else, like the notch on the flywheel in a 944.
I suppose one could use the cam end notches (used for locking the cams once at TDC) to determine TDC, then mark the crank pulley.