Bike Ressurection: Engine Knock

[cmarshall48]

So I purchased this bike about a month ago after it had sat for a few years, and after a full carb rebuild, carb sync, fluid change, and fusebox upgrade, it runs! This thing runs like a bat out of hell, but at idle, it sounds like something is knocking pretty bad.
I did a little research and found that some people say a little knocking after sitting can be caused by the rings being dry/ stuck or something like that, but this is still scaring me. Here is a video of the bike idling to give an idea of the noise it's making. Any help is greatly appreciated!

https://1drv.ms/v/s!AuDyYBPTiKNIhEkQoHG6mgoAkPhL

[FJ111200]

To me it sounds like something loose inside the timing cover which is tapping on the cover itself. Hard to tell really. Whip the cover off and have a look.
Also, where's that hose going to that comes from the vacuum advance which is located inside the timing cover as well.

[IanDMacDonald]

Just curious what the RPM's are? Sounds like it's lower than 1k?

[Ranger_xs1100]

knocking

My bike sounded like that when I had the vacuum advance line connected to the manifold input boot rather than the number 2 carb nipple. The engine rebuild that I envisioned and feared turned into a quick 30 seconds vacuum line move.

[DiverRay]

As Ranger said, it sounds like you have the advance connected to the carb boot instead of the carb body on #2. look at 4:50 into this video, the hose he is connecting is from the vac advance to carb body #2. http://www.xs11.com/forum/showthread.php?t=35349 I know it's not really clear, but it should give you an idea of where to look.

[cmarshall48]

The way I have my vacuum lines connected is this: long hose from cover to #2 carb brass Nipple, short hoses from carb boots to vacuum petcocks. Could it be that my vacuum advance isn't working for some other reason?

[cmarshall48]

Just curious what the RPM's are? Sounds like it's lower than 1k?

RPMs are right around 1200 at warm idle

[bikerphil]

The engine could also knock if the motor oil is too thin, perhaps 10W30 or contaminated with gas.

[tarzan]

There was a technical service bulletin related to the 80 engine regarding the vacuum advance. It would cause a knock, however it was determined not to cause damage to the engine. It was just annoying. However, they did offer an replacement advance to correct this, but obviously those are no longer available. I had an 80 Special with that problem. I worked on that bike a couple months ago for the guy I sold it to several years ago. It still runs strong to this day.

[Radioguylogs]

Cam Chain?

In case it helps, I had a similar sound after my Cam Chain Tensioner slipped.

I was reluctant to blame the CCT at first, because I had adjusted it when I got the bike back on the road after it sat for several years.

Easy to rule out in 10-15 minutes.

[cmarshall48]

The engine could also knock if the motor oil is too thin, perhaps 10W30 or contaminated with gas.

I just changed the oil to fresh 15w-40 and put in a new oil filter, so I doubt that would be it. The cheap in-line filters I put on did leak a little onto the crank case, but it wasn't much and the knock was present before that.

There was a technical service bulletin related to the 80 engine regarding the vacuum advance. It would cause a knock, however it was determined not to cause damage to the engine. It was just annoying. However, they did offer an replacement advance to correct this, but obviously those are no longer available. I had an 80 Special with that problem. I worked on that bike a couple months ago for the guy I sold it to several years ago. It still runs strong to this day.

Did it sound the same as this? Maybe I'll just ride it a while and see what happpens...

In case it helps, I had a similar sound after my Cam Chain Tensioner slipped.

I was reluctant to blame the CCT at first, because I had adjusted it when I got the bike back on the road after it sat for several years.

Easy to rule out in 10-15 minutes.

Thanks for the tip! I'll try adjusting mine tomorrow and see if anything changes.

[cmarshall48]

I pulled the timing cover today to see if anything was loose and could be hitting the cover, but all looked well to me. Here is another couple of videos to possibly help with a diagnosis? Thanks for all of the help so far guys, I really appreciate it!

https://1drv.ms/v/s!AuDyYBPTiKNIhEsH2prus-pvRnKZ


https://1drv.ms/v/s!AuDyYBPTiKNIhEr8U3UMYe-0eSaa

[Eastcoaster]

Imo

I don't know the RPM's sound too low to me?
I would tweek it up a hair and see. what happens.
Could the Tach be off?

[tarzan]

Ya, advance only rattles under load and at mid-ish rpm range. So probably more like time chain, unless it's a metalic knock, which would be lower end problem

[mack]

Rpm

That bikes idle is way too low. If you watch the vacuum pot actuator arm and listen to the knock, it's looks to be in time with the arm moving up and down.