What causes Worn valve seats causing hard starting on the Yamaha Yz450f?

Compression test, ask about last valve adjustment date Estimated fix cost: $300-$600

What causes Cracked or leaking radiators on the Yamaha Yz450f?

Inspect fins and seams for cracks or coolant stains Estimated fix cost: $150-$350

Grab swingarm and wiggle for play or clunking Estimated fix cost: $100-$250

Pull airbox, inspect filter condition and engine hours Estimated fix cost: $400-$900

Known issues to inspect before buying a used Yamaha Yz450f. What to check and how much repairs cost.

SERIOUS

Compression test, ask about last valve adjustment date

Fix cost: $300-$600

MODERATE

Inspect fins and seams for cracks or coolant stains

Fix cost: $150-$350

MODERATE

Grab swingarm and wiggle for play or clunking

Fix cost: $100-$250

SERIOUS

Pull airbox, inspect filter condition and engine hours

Fix cost: $400-$900

☐Run engine, check for smooth idle

☐Review maintenance records if available

☐Inspect frame for cracks near welds

☐Test all gears for smooth shifting

Reliable if maintained, punishing when neglected