Hello all, again
I have a 91 K100RS that has a knock when cold at rpms below about 1100.
The knock goes away before the temp gauge gets out of the blue, maybe after two to three minutes of running. In fact with carefull use of the enrichner lever you will never hear the knock. I've put 2k+ miles on the bike in the past month and the sound hasn't changed at all.
Having a heightened sense of 'searchness' i've spent a couple of days doing research on this site and all over the internet and have located information that points to the hydraulic cam chain tensioner as the culprit. The tensioner apparently has a ratcheting mechanism in it that holds a setting after oil pressure drives the piston out. The racheting provision has been known to fail according to an article on Flyingbrick.de, causing a cold knock (the article said 'bang') that goes away when the engine is warmed up.
Anyway, has anyone here had any experience with this? I would like to take the cam chain cover off this weekend and examine the tensioner but my service manual hasn't arrived yet and I don't know what all i'm getting into in regards to coolant, sensors, etc. The motor has 55k miles on it and has been run on Amsoil 20w50 it's entire life. I don't know how long the knock has been there as I am the 2nd owner. Also, the bike has a Staintune exhaust system. I am mentioning that because the knock sometimes sounds like it's comming from the muffler.
The best way I can describe the knock (to an experienced mechanic) is that it sounds like what you hear if you pull a plug wire off of a 4 cylinder motor. I've considered that it might be missing on one cylinder at start up and haven't completley abondon that idea. It does run very smoothly on start up though.
Also, I can feel the knock in the grips when it is at it's loudest. That would be at a slow idle right after a cold start up.
Any advice or experience appreciated. thanks, Bruce
I have a 91 K100RS that has a knock when cold at rpms below about 1100.
The knock goes away before the temp gauge gets out of the blue, maybe after two to three minutes of running. In fact with carefull use of the enrichner lever you will never hear the knock. I've put 2k+ miles on the bike in the past month and the sound hasn't changed at all.
Having a heightened sense of 'searchness' i've spent a couple of days doing research on this site and all over the internet and have located information that points to the hydraulic cam chain tensioner as the culprit. The tensioner apparently has a ratcheting mechanism in it that holds a setting after oil pressure drives the piston out. The racheting provision has been known to fail according to an article on Flyingbrick.de, causing a cold knock (the article said 'bang') that goes away when the engine is warmed up.
Anyway, has anyone here had any experience with this? I would like to take the cam chain cover off this weekend and examine the tensioner but my service manual hasn't arrived yet and I don't know what all i'm getting into in regards to coolant, sensors, etc. The motor has 55k miles on it and has been run on Amsoil 20w50 it's entire life. I don't know how long the knock has been there as I am the 2nd owner. Also, the bike has a Staintune exhaust system. I am mentioning that because the knock sometimes sounds like it's comming from the muffler.
The best way I can describe the knock (to an experienced mechanic) is that it sounds like what you hear if you pull a plug wire off of a 4 cylinder motor. I've considered that it might be missing on one cylinder at start up and haven't completley abondon that idea. It does run very smoothly on start up though.
Also, I can feel the knock in the grips when it is at it's loudest. That would be at a slow idle right after a cold start up.
Any advice or experience appreciated. thanks, Bruce