Time for a rebuild

Radio Control Car Action, Dec 2001 by Cummings, Chris

Time for a rebuild

I have an HPI Nitro Rush with the stock Nitro Star .iSFE engine. I have run three gallons of fuel through the engine. The engine has great compression (enough to lift the truck off the ground when I try to start it), but after a minute or so of running, it sputters and dies out. I checked the high-speed needle setting and adjusted the throttle trim correctly, but the engine still dies after a few minutes of running. I run Wildcat 20-percent nitro with 14-percent oil content.

CHRIS CUMMINGS, Bradenton, FL

Your engine has all the telltale signs of needing a rebuild, Chris. The seal between the piston and sleeve is designed to be tight when the engine is cold, but as the engine warms up, the sleeve (which is made from a softer metal than the piston) starts to expand, allowing the piston to move up and down inside the sleeve with less friction. Over time, the gap between the piston and sleeve can become too big, and that can cause a compression problem such as you now have.

Replace the piston and sleeve, and your problems will be solved (see "How to replace a piston and sleeve" in this issue). I also recommend that you replace the connecting rod at this time as well. After you've rebuilt the engine, repeat the original break-in procedure that HPI recommends in the Rush manual.

TOOL BOX

DuraTrax Pit Tech car stand

Most wrenching can be done right on the bench top, but for jobs like installing wheels, setting speed controls and tuning engines, a car stand is a must. DuraTrax's Pit Tech model is the best I've tried; it has grippy rubber strips to hold the chassis and a relieved center section that prevents cars like the Team Losi Triple-X and Associated B- and T-series from rocking on the stand. A deep tray prevents small parts from wanderin off, and the whole magilla stores compactly when not in use.

DuraTrax Pit Tech car stand-part no. 2370; $12.