Author Topic: CB550 lower end knock video HELP (Read 5416 times)

Flying J · « **on:** March 31, 2012, 03:09:58 PM »

Here is a video. Its sound a little worse in the video then it actually is but its lower end knock that goes away as the rpms hit about 3k. Im not sure what is causing it.
Cb550 engine knock

geminimotors · « **Reply #1 on:** March 31, 2012, 03:30:16 PM »

I have a similar issue with my 76 550F. It goes away at about 2k. I'm curious to hear what people think.

LesterPiglet · « **Reply #2 on:** March 31, 2012, 03:30:36 PM »

Did this just start or has it been going for a while? Clutch or primary chain is my guess.

geminimotors · « **Reply #3 on:** March 31, 2012, 03:43:42 PM »

I just went out and had a look at mine. The noise had gotten progressively worse in the last two weeks. The three bolts attaching the stator to the cover were loose. Tightened them up and the noise quieted down significantly. There is still something faintly rattling in the bottom end that goes away at about 1800 rpm.

LBM 550F · « **Reply #4 on:** March 31, 2012, 03:51:06 PM »

Sounds like a exhaust leak to me, Is the bottom rusted through one of those pipes?
L.

LesterPiglet · « **Reply #5 on:** March 31, 2012, 03:57:13 PM »

And the exhaust leak seals itself @3000 rpm!

Flying J · « **Reply #6 on:** March 31, 2012, 04:00:11 PM »

No, its a knock coming from the motor not the exhaust.

LesterPiglet · « **Reply #7 on:** March 31, 2012, 04:04:10 PM »

Any difference in sound when you pull the clutch in?

Flying J · « **Reply #8 on:** March 31, 2012, 06:03:46 PM »

No, but it sounds very similar to that clutch noise but louder. I checked the 3 screws under the left cover. They were tight.

Im wondering if this is what the primary chain sounds like.

Greggo · « **Reply #9 on:** March 31, 2012, 06:08:26 PM »

Quote from: ffJMoore on March 31, 2012, 06:03:46 PM

Im wondering if this is what the primary chain sounds like.

That would be one of my first guesses, considering 'we' don't think it's the clutch rattle, misadjusted valves, or an exhaust leak..I also think that when the rpms go up, the tension on the primary chains would increase, and that may be enough to pull the chain from the interior wall of the case.

Have you pulled the pan to check if it's rubbing?

bwaller · « **Reply #10 on:** March 31, 2012, 08:07:42 PM »

Don't run it anymore until you synch your carbs! At least eliminate one potential problem.

Flying J · « **Reply #11 on:** March 31, 2012, 08:21:44 PM »

They are synced. But i wonder if one rattled lose. I'll have to double check that.

Flying J · « **Reply #12 on:** April 01, 2012, 08:13:37 AM »

Bwaller you may be right on the money. I went out last night and checked sync adjustment screws and the #1 was lose. When I'm free this afternoon I'll check the sync and see how far that one has wandered. If that's it i will be so happy.

bwaller · « **Reply #13 on:** April 01, 2012, 08:20:33 AM »

Here's hoping you're riding with a smile on your face this afternoon.

WarwickE36 · « **Reply #14 on:** April 01, 2012, 03:07:51 PM »

My primary chain made some noise very similar to that. Check my posts, I have videos of it with the oil pan pulled, then with the motor pulled with the cases split and then again with the new chain for comparison.

Flying J · « **Reply #15 on:** April 01, 2012, 09:15:03 PM »

Syncing the carbs helped a bunch. It still has a little knock but not bad. I will check the primary chain next time i change the oil. The bike ran fine for a few blocks but then got real jerky in mid range throttle. Then it got even worse. The exhaust smelled like fuel. checked the plugs, 1&2 they were black. So i dropped the bowls.

I think i need to do a better job tightening things down.

grcamna2 · « **Reply #16 on:** April 01, 2012, 09:21:45 PM »

ff,
That's a clue..for sure !

Is that Permatex "High Tack" gasket sealer that I notice around the bowl gaskets ? if so..that could be part of the problem.It may be getting into you're pilot jets. I think you should clean up the pilot circuit & jets real good & don't use any gasket sealer on you're carb. bowls..just the standard,pliable gaskets.

seanbarney41 · « **Reply #17 on:** April 01, 2012, 09:29:26 PM »

...really doesn't matter if jets are clean or plugged when they are sitting in the bottom of the float bowl

grcamna2 · « **Reply #18 on:** April 01, 2012, 09:32:00 PM »

Quote from: seanbarney41 on April 01, 2012, 09:29:26 PM

...really doesn't matter if jets are clean or plugged when they are sitting in the bottom of the float bowl

I'm with you there !

Flying J · « **Reply #19 on:** April 01, 2012, 09:51:03 PM »

Quote from: grcamna2 on April 01, 2012, 09:21:45 PM

ff,
That's a clue..for sure ! Is that Permatex "High Tack" gasket sealer that I notice around the bowl gaskets ? if so..that could be part of the problem.It may be getting into you're pilot jets. I think you should clean up the pilot circuit & jets real good & don't use any gasket sealer on you're carb. bowls..just the standard,pliable gaskets.

Not sure what it was but it's just residual and would be real hard to scrub off. Its not getting into the bowls. The carbs are clean and I have not had any problems with junk in the carbs since i put on a petcock with a filter. These last 2 problems have be my own fault. Ill be gone for my anniversary for a few days but when i get back ill ride the hell out of this bike and see what problems i can turn up. Thats generally how i do it.

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Author Topic: CB550 lower end knock video HELP (Read 5416 times)