Motorcycle Repair/topend knock


i have a 1984 650 nighthawk with 22,000 it sat in a field for 3 years i recently restored it with parts from a 85 nighthawk it eventually started and after 10 minutes of smoke she ran pretty good. on its maiden voyage she developed a slight tap that turned into a solid knock ( top end ) by the the time i was able to pull off the highway the oil light was flickering and the the bike shut off after a half hour she started and ran but no power! i limped it home and with a complete oil flush she seems to be okay except for the top end knock. MY QUESTION IS bad oil pump or is this bike prone to faulty lifters

Hi Joe,

It sounds like it might have oil pressure problems but I would
pull the top engine cover and see if it is getting any oil up there.
The camshafts could be running dry and starting to knock
against the dry valve lifters. It doesn't take much for the
camshafts to make noise. Also the cam chain tensioners
use oil pressure to keep them tight.

The oil light is not a reliable oil pressure check so the
pressure should be checked with a gauge where the oil light sensor
screws into the engine.

The oil pump uses a number of rubber orings that could
have blown out and need replacing.

The lifters could make some noise but a hard knock is usually
lack of oil or camshaft lobe wear and excess end play.

If you can verify the top end is getting oil pressure
then you can go on checking the camshafts, lifters
and cam chain for problems.

If the oil pump is good it has about 90 psi at 6000 rpm.
The top end should be wet with oil if you look under the top cover.

The lifters can be soaked in solvent, cleaned  and then pumped up
with some fresh oil.

Oil pump is inside the bottom oil pan but requires removing
exhaust pipes to inspect. Some orings are accessible there
but pump removal needs the clutch removed as well.

Hopefully your oil pressure is now okay to the top end
and no damage has been done. Often when bikes sit unused
things can get sticky and orings and gaskets can dry out.
As long as you have oil pressure some running might help
the engine liven up the  seals etc.


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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