Break-in info for Knucklehead, Panhead, Shovelhead & Evo engines.

Note: These engines must be broken in. They will feel extremely strong, so resist the impulse to turn it on. Break the engine in correctly.

Accurate Engineering Break-In Procedure
This procedure applies to all engines with close fit pistons.

• On the initial engine startup, don't sit and idle motor while you admire your work or tinker with the minor adjustments. Heat buildup can be excessive. Do not let the engine overheat.
• The first 50 miles are most critical for new rings and piston break-in. Most engine damage will initially occur during this period. Keep heat down by not exceeding 2500 RPM. Vary your speed. DO NOT LUG THE ENGINE. NOTE: Re-torque all applicable areas: head bolts, pan covers, intake clamps, and exhaust clamps. Refer to the applicable engine torque spec sheet for proper torque values.
• Next 500 miles should be spent running engine no faster than 3500 RPM or about 50 to 55 mph. DO NOT LUG THE ENGINE. VARY YOUR SPEED. NOTE: Re-torque all applicable areas: head bolts, base nuts, oil pump, tappet blocks, gear case cover, crankcases, pan covers, intake clamps, and exhaust clamps. Refer to applicable engine torque spec sheet or proper torque values.
• For the balance of the first 1000 miles, speed can be run up to 60 to 70 mph. Continue to run engine at all different speeds including lower 40 - 45 mph ranges. DO NOT LUG THE ENGINE.
• 1000 - 2000 miles basically same as before, but a little more liberal with the RPM range. Avoid overheating and lugging the engine. No drag racing or trailer towing.
• Oil changes 100 miles, 500 miles, and ever 1000 miles thereafter
• After 2000 miles .......HAVE FUN.

Caution - lugging engine at low RPM's and/or running the engine prematurely at high RPM's may result in damage to the pistons and/or other engine components. Accurate Engineering voids warranties if the engine is not properly broken in.