Chain

Properly maintained, the chain should last you approximately 1000 miles or one season of use.  Each aspect of chain maintenance is critical to its reliable function:

Lubrication

Lubricate the chain with a quality chain wax before each session, OR at the end of each session. See the Fluids section for some recommendations on suggested products.

Tension

Chain play should be set at approximately ½” to ¾” of play from one extreme of movement to the other (i.e. full up and full down as you tug on the chain). Rotate the sprockets to check this in several spots, as most chains will have a ‘tight spot’.  Set the aforementioned tension at the chain’s tightest spot.

Tension is set on the Stohr by moving the rear differential carrier forward and backwards.  Two bolts on the right side of the spar loosen the carrier in its mounts.  Two nuts mounted at the rear of the spar, connect to eyebolts, which are in turn attached to the diff carrier.  These are used to pull the differential backwards.  To move the diff forward, rotate the nuts counterclockwise to get some ‘slack’, then tap the differential forward with a rubber mallet until you have things as loose as you need.  When you’re done, tighten the two bolts on the right, and make sure everything is aligned.

Tips

• The pinch bolts on the side of the diff case (5/8” head) should be very tight to avoid movement.  Use a long-handled 3/8” ratchet to get them snug.
• You can make a “diff push bar” out of a long piece of 1” square tube.  Shape one end into a “cup” that roughly matches the diameter of the aluminum cylinder inside the spar.  Tapping that forward will move the diff forward without having to bash on your CV joints.
• If there is a LARGE difference in tension from tightest to loosest spot on the chain, i.e. the chain sags when at its loosest spot, the chain may need to be replaced.  If in doubt, call Stohr or an experienced Sports Racer mechanic.
• If you find that you have trouble keeping the chain tensioned, or have very short chain life, it is likely that the rear differential carrier bearings have failed.  You can test for this by trying to rattle the differential in the carrier, or by pulling on the cups that the axles bolt to.  Replacement requires removing the differential, and the bearings are about $75 each.

Alignment

Check chain alignment with a straight edge, placed on the face of the rear sprocket, lined up with the front sprocket. An alternate method is to buy a “Pro FI Laser Cat”, which shines a red laser along the chain with which you can check alignment.  This tool is about $100, and available from various online sources.  Contact Stohr or post on the forums  if you have difficulty locating one.

See the Fluids & Consumables section for suitable replacement drive chains. Use only rivet-type master links NEVER clips. 

Chain Breaker / Riveter

RK’s steel chain breaker is a good breaker.