Knocking sound at idle?

[Guest]

Got the bike up and running again today (thanks for tips on the oil change). She ran pretty good despite needing rejetting (4-1 and pods). When at idle though, there was a rhythmic knock sound coming from the engine. It would stop when revved or being ridden. Any ideas? Thanks for all you help everybody!

[tkent02]

Clutch rattle? Carbs out of synch? Exhaust leak?

[1948man]

Maybe search "cam walk" or "cam end float". Also possibly clutch noise. I'm not the expert to really describe it all.

[GS750cafe]

Sucks to be so illiterate with motors, but I'm learning! The sound is definitely not the carbs or exhaust. I don't think it's the clutch either. Sounds like it's coming from the depths of the engine... maybe something to do with the cam. Seems like it's more pronounced once it's warmed up good and then idleing. I drove VWs buses for a while, and there was always talk of knocking sounds being associated with throwing a rod. But, there aren't rods in this motor are there? Cheers

[tkent02]

It's got connecting rods, but they don't go bad much. Unless you have a 1980 - 1982 750.

[GS750cafe]

This is a '77 GS750 with just over 12k original miles on it.

[tkent02]

No, that motor is just about indestructable with ten times that many miles.
It's not going to be a bad rod. Have the carbs been synched?

[GS750cafe]

Not sure. I just bought it a few weeks ago. The throttle response seems good. Its just when I ride, then stop there is the knock or tick about aver second or so at idle.

[tkent02]

Like tick, tick............................tick, tick................................tick, tick?
Quite a long interval between each pairs of ticks?

[Steve]

Yep, sounds like "cam walk".

Rather than "revving" the engine, increase speed slowly. If the noise goes away between 12-1500, it's almost guaranteed to be cam walk.

More annoying than destructive, many of us just live with it, although a few have found cures.

.

[GS750cafe]

I don't recall much time between pairs of ticks. More like tick...tick...tick...tick
But I might have to start it again to get a better sense. It's almost like you can feel the tick...

[Steve]

Can you get a video (or audio) recording and post it?

.

[GS750cafe]

I'll see if I can't get some (video/audio) tomorrow. Although I think it's snowing outside and I don't have a garage! We live in a barn (literally) and I'm working on the bike in a horse stall! Talk about horse power!

[GS750cafe]

[youtube]watch?v=N9bha5LVJAs[/youtube] <--- that didn't work.

Until I figure out how to embed video, her is the youtube link: http://www.youtube.com/watch?v=N9bha5LVJAs


Aside from the exhaust leak, you can here the ticking sound at idle. Now that I hear it again, tkent02, you might be right.
Let me know what you think.
Cheers

[chuck hahn]

My money is on the clutch basket springs being worn out. I got a 77 and a 78 with both of them being over 35,000 miles and not as much as a fart out of the top ends..the early 80s..now those are different animals all together!! I say pull the basket and i bet the springs are loose. Theres a lot of in fo on here about rebuilding the baskets and i even think there are afew places you can send them out for repair as well.