78 xs650 knock

[WV Sparky]

Hey fellas, my xs developed a strange knock this week when riding home from work. I first noticed it when at a stop light letting out of the clutch I could feel it knocking through the frame “hardtailed, rigid mounted engine” at normal cruising speeds the vibration/knock isn’t present. It’s only at low or bogging RPM such as shifting into a higher gear and rolling into the throttle. I have a video of it doing it at idle after getting home that even which unfortunately was about 50 miles after the issues arose. I’m not sure how to post it here though I could email it to anyone interested. I have yet to check the valves and timing chain tensioner but they were just adjusted this spring maybe a 1000 miles ago. Any tips for where to look would be greatly appreciated. Thanks guys!

 

[jetmechmarty]

Upload your video to YouTube. Use the media insert icon to post the video here.

 

[WV Sparky]

Here’s the video, posted on YouTube

 

[JJames]

Here’s the video, posted on YouTube

Ouch!

 

[jetmechmarty]

I think it’s going to have to come out.

 

[WV Sparky]

Thursday evening I went to start trouble shooting the bike starting with valves and timing chain, took the PMA cover off to roll the bike over to TDC and found that my PMA nut had came loose. Re-Torqued with a couple extra LBFT’s and the noise is gone. Went ahead and dropped the oil pan to check for metal in the pan and on the sump, all is good now. I appreciate it guys!

 

[Its been a long time]

Thursday evening I went to start trouble shooting the bike starting with valves and timing chain, took the PMA cover off to roll the bike over to TDC and found that my PMA nut had came loose. Re-Torqued with a couple extra LBFT’s and the noise is gone. Went ahead and dropped the oil pan to check for metal in the pan and on the sump, all is good now. I appreciate it guys!

Good job there's no consequential damage. Well done finding the problem.

 

[WV Sparky]

Good job there's no consequential damage. Well done finding the problem.

I appreciate that, learned everything I know from you guys!

 

[Its been a long time]

I appreciate that, learned everything I know from you guys!

I've seen it where a person has been convinced their main bearings have failed. It turned out the alternator rotor nut was loose. It's surprising how it sounds much more serious than it is, as long as it's caught quickly before it goes on to cause other problems.

 

[WV Sparky]

I've seen it where a person has been convinced their main bearings have failed. It turned out the alternator rotor nut was loose. It's surprising how it sounds much more serious than it is, as long as it's caught quickly before it goes on to cause other problems.

Funny you should say that, I was almost sure that’s what it was. It never even crossed my mind that the nut could’ve been loose, although at the time I had a hard time figuring a way to get the bike to hold still while I torqued it. I bought a motorcycle lift stand since then, so I strapped the wheel and frame down this time and made easy work of it.