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YZ450F4

abnormal engine knock!

2 posts in this topic

I got my bike back together today. Has a fresh crank, bearings, cylinder, piston and rings, and valves. It started second kick today. First time the motor has been ran with the new internals. It ran fine so i heat cycled the first time, let it cool and went to heat cycle it again. (i heat cycle it three times before i ride it) It ran for about 8 minutes the second time i cycled it and then it started a real loud engine knock. I know yzs have a normal engine knock but its five times as loud as my YFZ450 and as my YZ was before rebuild. Took it apart, timing is dead on. Valves appear to be good also. Pulled the clutch apart and all the gears look to be good and where they should be. Put it back together and it fired right up but it still had the god awful engine knock. I shut it down immediately. Has anyone else had this problem?:smirk: Any help would be apprecitated. Thanks

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Did you take the ignition cover, and flywheel off for further inspection? I've heard of the timing chain guide bolts backing out before and making some noise. Was the chain replaced? It's a good habit to start spraying carb cleaner into the bolt holes to clean out any oil that sneaks in, and using loc-tite. I've never ran mine low on oil before, but I believe that might make some noise also???

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