The holding valve being built into the TCV became standard in late 1985. Yours did not come from the factory with one. You can purchase either a TCV with holding valve built in and drill new holes or find a suitable holding valve and install it. About $200 - $250 either way you go. It is usually best to learn about the different models of holding valves and the different tubing they used so you make sure and get the correct one. Fortunately, many if not all of the tubes have been reinstated into stock very recently. New tubes are not cheap, but if you could find a valve for the right price it would be worth it. Maybe you could find one for sale without tubes real cheap from someone not aware new tubes were recently reintroduced. If it does have a holding valve already installed, you will see a relatively small rectangular steel device right in front of where the tubes attach to the drive motor. There will be three very tightly bent tubes connecting things. I feel a holding valve is necessary unless you have very flat property. Racing downhill can be frightening. It should have a "retard " position on the travel control lever which acts as a holding valve. To use it, the throttle must be wide open and the lever must be properly adjusted. Refer to your owners manual for info.
Contact Brian Hildreth for info and prices on tubes.
Edited by BowlBuilder, April 08, 2014 - 04:57 PM.