Developed a Bottom End Knock,got a question.

[XS650D]

I noticed a light knock last season which has gotten louder this year,now very noticeable
even to my wife and she notices nothing regarding my bike.It sounds like its coming from the bottom end,Kick start side.What I have noticed is it will start rite away on cold start up and gradually get louder.
If I increase rpm to 2000 rpm it will disappear.Also after a good ride I no longer notice it at idle.
Its not valves,clutch related ect.I will try and post a video.Based on what I have mentioned does it sound serious.I do find it strange that the knock will go away when engine warmed up good after a ride.

 

[TwoManyXS1Bs]

This is one of those that's best tracked with a mechanic's stethoscope.

For now, given your strange description, I can only guess at three wild possibilities.

- Something is oil-dry at startup, eventually gets oil, and quiets down.

- The oil thins quite a bit after warm-up. Cold starts have higher oil pressure, around 15-25 psi, which drops to darn near zero when hot. Something about the oil pump could be reacting to the higher pressure, then calms down when the oil pressure drops.

- The kickstart 'bendix', or the electric starter 'bendix', near the crank gearteeth, may not be retracting properly, until sufficient engine vibrations let it jitter clear...

 

[XS650D]

Ok Thx TooMany,don't own a steth but have decided to pull the side cover and just mak sure everything is
tight first,this bike to totally dismantled for rebuild including motor,clutch ,new rings ect when i got it i noticed alot off loose bolts everywere including the nut for the stator/rotor.I woulent be surprised if something was loose
in the clutch side,do i need a new gasket when i pull it ,its been changed,looks new.

 

[TwoManyXS1Bs]

Ok, that paints a slightly different picture. LooseBoltItis. Some members have reported knocking sounds when parts of the exhaust are loose.

Tough call on a first-time pull of a cover, since you weren't there to oversee its installation, or if sealer was used, or if the surfaces weren't properly cleaned before cover reinstall, or who-knows-what-else. On initial removal of the clutch cover, if the mating surfaces look clean/flat, and the gasket isn't torn/squashed/warped/hard, then you might be able to re-use it.

If you do a good cleaning/levelling of the mating surfaces, and smear a very thin coating of grease on both sides of a new gasket, then you're starting from a known condition, one that should let you pull the cover sometime in the future, leaving the gasket intact, and useable for a couple more times.