Loud knocking

[81GS550L]

I just took out my 81 GS550L to get it ready for spring. It started right up. I was blowing out a little black carbon w/a few revs, nothing too crazy. Then all of a sudden something gave and now there's a knocking, more so than I would say a tapping or clicking. But only at high revs, When idling it sounds fine. Any ideas? Thank you in advance.

[BassCliff]

Knock, knock. Who's there?

Anita.

Anita who?

Anita find out where the knocking's coming from! :-D


Hi Mr. 81GS550L,

Can you pinpoint where the knocking is coming from? From the top near the cam chain? From the bottom on the rotor side? Use a screwdriver, pointy end touching the motor, handle stuck in your ear.

Thank you for your indulgence,

BassCliff

[KRISTI'SGS550]

You might need a partner to help you pinpoint the problem, especially if you use the screw driver technique. Since the bike only makes the noise at high RPM's you will have to listen to it while someone tries to get the RPM's up. I don't think this technique will work while riding, I wouldn't try it.

Cory

[81GS550L]

It sounds like the top, more towards the right side.

[BassCliff]

Hi Mr. 81GS550L,

Did you change the oil before you started it up? Could it be the tach cable drive gear that's gone buggery? You might want to pull the valve cover off just to have a look. Keep us informed.

Thank you for your indulgence,

BassCliff

Oh, yeah. I think it would be a wise move NOT to be riding your bike while listening to the motor with a screwdriver. Words to live by Mr. Cory. :-D

[81GS550L]

No, I didn't change the oil. I hope it's just the tach cable. Thank you guys very much for the responses.

[earlfor]

I would remove the valve cover and start it up. You will be much better able to hear top end noises. It will be a bit messy/oily, but not horribly so.
You will also be able to check for a loose cam cap bolt. If its a good, loud knock, it may be a loose bolt. I had that happen once and it was so LOUD. I thought I had thrown a rod bearing. :-)

Earl

[81GS550L]

I have a few warm days coming next week, I'll sure check out everything you guys mentioned. It was pretty loud, but it actually ran smooth. If it were something major I would figure the engine to just stop running.

[earlfor]

If a cam cap has come loose, it will still run smooth/normal at low rpm.
Let us know what you find.

Earl

I have a few warm days coming next week, I'll sure check out everything you guys mentioned. It was pretty loud, but it actually ran smooth. If it were something major I would figure the engine to just stop running.

[81GS550L]

Well there was no way I could wait to open it up. It's a shim, damn thing exploded. And after inspecting the others, the top left one is also cracked. I think not knowing what the problem was, is worse. Is this a part that is still readily available?

[DanTheMan]

Yep, there's even a shim swap thread on this site. See if you can read the numbers on yours and ask for something in that general range..:-D

Well there was no way I could wait to open it up. It's a shim, damn thing exploded. And after inspecting the others, the top left one is also cracked. I think not knowing what the problem was, is worse. Is this a part that is still readily available?

[Dogma]

Wow, 2.6mm of clearance...

How does that happen? Dirt under the shim maybe? PO fabbed a shim that was too brittle? In other words, how do I make sure that doesn't happen to me?

[BassCliff]

Wow, I've never seen a shim break before. I don't know what would cause that. You can order new ones at www.z1enterprises.com for $4.75 each. Make sure you get the 29.5mm diameter shims. Please don't run your motor without all the shims installed.

Thank you for your indulgence,

BassCliff

[81GS550L]

Excellent! that's great they're cheaper than used ones on ebay. How do these install? Do they slip in or do I have to remove the cam shaft? And how does that work w/the timing chain?

[lurch12_2000]

Not to aggravate your situation, but wouldn't you want to check the cam lobes for damage before installing new shims?
There was another recent post describing shims breaking and concern with grinding them down to a lower size, which might weaken them.
Has anyone else had shims break on them? Is this reason enough to go with new shims as opposed to trading old shims around?
Or is it that owners are over revving their engines?