2020 Yamaha YFZ450R SE trouble

[onionring89]

my BIL got this issue with his 2020 Yamaha YFZ450R SE.

He just replaced the cases because of a popping chain issue on the bottom end.

Now he's getting ready to put the top end back together, but he noticed something weird when he turned it over by hand.

He says it hits a rough spot when he rotates it, then it smooths out, and then at the exact same spot again, it gets rough.

Everything felt super smooth until he started buttoning up the bottom end, like the clutch, timing chain, guide, all that stuff.

I'm helping him, but also totally stumped, anyone got some ideas on what might be causing that rough patch?

 

[RaptorChaser]

Sounds like something's dragging on every rotation. Could be a rod bearing starting to bind or maybe the timing chain guide not seated right.

Quick question, did he check crank end play and rod side clearance after buttoning up the bottom end? And is the timing chain tensioner installed yet or still loose?

Might be worth pulling the clutch side cover again to double-check.

 

[Dylan1]

It could be a misaligned crank bearing or a warped case half from improper torque sequencing. People blame clutch or timing components, but internal misalignment after case replacement is more common than most realize.