Saturday, October 15, 2011

8-25 Bike Seized Up

8-25 Bike Seized up. 15hrs  I was riding the bike on the highway at 60 MPH and it seized the left cylinder. After much investigation both at the shop that bored the cylinders and dialoging with the guys on USA 2strokers forum, I was able to properly diagnose the issue.
  1. Wrong piston clearances: The cylinders were bored to fit stock cast aluminum pistons. The pistons installed were Wiseco FORGED aluminum pistons. Forged pistons expand more so a few thousands off on the clearances and you can have a seizure. in my opinion the bike shop should have known this when I brought the jugs and the over sized pistons to them, but ultimately it was problem because I did not check the clearances after I got the pistons and jugs back. Lesson learned: don't trust even a reputable bike/machine shop; check all factory/mfg recommended clearances.
  2. Slightly Lean Carburetor jetting: I drove the bike for 300 miles without issue, but I was only driving stop sign to stop sign, not highway driving. When I took the bike on the highway at 60MPH the carb was operating in the main jet / jet needle range, and was slightly lean. Being slightly lean did not cause the bike to seize but it added HEAT to the equation. Heat + tight piston clearances = seizure

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