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Motorcycle Repair/Motorcycle engine knock


I have a 2008 Lifan (clone of 250 V-Twin Yamaha) with serious-sounding engine knock above idle.  It started suddenly 10 miles after some engine work that included loosening up shifting.  At first was loud "squawk" in time with engine turning over.  It settled to just knock that seems low in engine with stethescope.  Engine has good compression, adjusted valves, sounds same if running on either or both cylinders.  I had lighter weight oil temporarily trying to loosen up shifting.    I can see if crankshaft isn't tight but flywheel nut seems tight through the little hole.  Am wondering if it is faulty oil pump.  Thanks

Hello Wayne,

Most probably your crankshaft and/or connecting rod(s) gave up. It's a common issue...
Lifans are hardly clones of anything! They're the worst Chinese copies ever...

In Greece, when a Lifan starts knocking, we don't even bother to open the engine.
We discard it, and put a new one on... till next time!

Sorry for being a bad-news-messenger, I really wish to be totally wrong, but all Lifans I've treated (50 - 250cc) suffered from severe crankshaft bearings and connecting rod seizure.

Best Regards,

Motorcycle Repair

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Lazaros Ampatzidis


I can help you on EVERY issue involving POST-1980 Japanese Motorcycles plus KTM and Husaberg. My field of expertise includes Engine, Transmission, Fuel system (carburation & EFI),Electrics and Electronics. Maintenance, repair and tuning. Road and off-road suspension tuning. Please don't ask me about non-Japanese Motorcycle, especially American built on which I have low to zero experience.


I'm a rider and hobbyist since childhood. 25 years motorcycle workshop mechanic.15 years motorcycle racing mechanic. In order of experience high to low:Kawasaki,Suzuki,Honda,Yamaha,KTM,Husaberg.

Hellenic (Greek) Technical School.Internal Combustion Engines Engineer. Automotive Electronics.

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