Engine knock...how bad is this?

[Guest]

I bought this '82 650G about a month ago with 16k miles. It was all original, and seemed to be in great shape mechanically. I changed the oil about 2 weeks ago with Rotella T and an OEM Suzuki filter. I've put about 400 miles on it since the oil change w/o issue.

About halfway through today's ride (I was flogging it pretty hard), it began to tick from the right side cam area. The ticking would only occur when the engine was under load, and go away when coasting or under a constant throttle. Being a hundred miles from home, I decided to keep riding. The tick stayed the same until I was @ 20 miles from the house, and it became more of a knock and increased in volume.

I knew it wasn't good, but decided to press on. A few miles later, I could tell it was beginning to lose power...and after a few more miles, I got caught by a red light. As I slowed and pulled in the clutch, the oil light came on and the engine quit.

How bad is this?

http://vimeo.com/104884861

[Rob S.]

Brother, I'm neither a mechanic nor a diagnostician. But it doesn't sound good. Get thee to a nunnery!

[Brendan W]

http://vimeo.com/104884861[/URL]

With my optimistic hat on, this is consistent with the clutch nut being loose. The oil pump can lose drive. I think your motor has helical primary gears so the clutch will move in and out depending on whether drive is applied or not and pulling the clutch can pull the oil pump drive out of engagement. I don't know what kind of view you have from the oil filler but I would open it, put the bike in top gear, rock it back and forth and see if the basket moves in or out.When the clutch is pulled does the whole assembly move.

[tom203]

With my optimistic hat on, this is consistent with the clutch nut being loose. The oil pump can lose drive. I think your motor has helical primary gears so the clutch will move in and out depending on whether drive is applied or not and pulling the clutch can pull the oil pump drive out of engagement. I don't know what kind of view you have from the oil filler but I would open it, put the bike in top gear, rock it back and forth and see if the basket moves in or out.When the clutch is pulled does the whole assembly move.

Yes, this makes sense, but maybe the engine just lost oil (leak?)- first noise at cams as pressure drops, then at crank with more drop and finally oil light comes on at 10psi.

[mrbill5491]

Yes, this makes sense, but maybe the engine just lost oil (leak?)- first noise at cams as pressure drops, then at crank with more drop and finally oil light comes on at 10psi.

If you lost oil from a leak it would obvious as hell. It would be all over somewhere on the bike. Did you do any maintenance on the bike besides the oil change?

[kwb377]

No oil leak...I also drained the oil when I got it home last night to check for metal bits or other signs of damage, nothing.

The only mechanical things I've done (aside from brakes/tires) have been the oil change, removing the clutch/breaker/stator covers to clean/polish and replaced those gaskets, and remove the exhaust to clean/polish.

Judging by the look of the cam cover gasket, and the torque values and valve specs hand-written in the included manual, the p.o. had recently done a valve check.

Although I'm mechanically inclined, I've never disassembled/rebuilt an engine...so this should be interesting.

[tom203]

A slow leak over 400 miles might be missed- filter cover or problem at secondary drive cavity. And 60 psi can find places to escape! I don't like surprises, that's why I check oil level before every ride.

[kwb377]

Oil level was showing at the "Full" mark last night before draining.

[rapidray]

From your description, it sounds like you could have a spun bearing.
Ray.

[kwb377]

From your description, it sounds like you could have a spun bearing.
Ray.

Unfortunately, that's my amateur diagnosis also. I took the cam cover off the inspect the top-end bits...






Clutch hub nut was tight, and oil pump unobstructed...