How to Adjust a Mini Bike Chain: Slack, Tension Nuts and Lube

What you need

• Wrenches or sockets for the axle bolts and tension nuts
• A ruler or tape measure
• Chain cleaner and chain lube
• A stand to lift the rear wheel, if the bike allows (dirt bike stands)

Step by step

1. Shut off the engine and let it cool. Put the bike on level ground or a stand.
2. Find the tightest spot: rotate the rear wheel and measure slack at the midpoint of the lower run at several points.
3. Loosen the axle bolts (under the engine on the rear axle assembly, on the CT200U).
4. Turn the tension nuts on both sides of the bike by the same amount. Clockwise tightens the chain; counterclockwise loosens it.
5. Keep the wheel straight: equal turns on both sides keep the axle square to the frame.
6. When slack reads 1/2 to 3/4 in (15 to 20 mm), retighten the axle bolts.
7. Re-check slack, then spin the wheel to make sure it turns freely.

Clean and lube

Coleman says to lube the chain before each ride: clean it with chain cleaner, then apply chain lube. Inspect for wear, rust, binding links and damaged sprocket teeth, and check sprocket nuts for tightness.

Signs it is time for a new chain

From Coleman's chain and sprocket inspection list

Sign	What it means
Will not hold the slack spec	Chain is stretched
Stiff or binding links	Worn or rusted pins
Hooked or broken sprocket teeth	Sprockets worn; replace with the chain
Chain jumps off	Too loose, worn, or sprockets out of line

Replacement chains by size are in the best mini bike chains. Jackshaft Colemans use a 420 set with a 90-link and a 42-link chain; a chain tensioner helps keep the jackshaft chain in place (per the Amazon listing).

Torque converter belts are different

Belt slack on a torque converter is set another way: King Midget Car Club's shop notes on Comet torque converters suggest 1 to 1-1/2 in of slack halfway between the pulleys. See torque converters. Chain checks fit into the maintenance schedule at every use.