Topic: CB500k1 knocking noise at idle.

[Andey108]

Hi all,

I’m experiencing a knocking noise at idle… I’m sure it’s happening when I rev, but the noise isn’t as obvious.

Any ideas where to look to fix it?

Video at idle here:
https://youtube.com/shorts/DxMlFn47smQ?feature=share

[newday777]

Welcome to the forum Andey108
That definitely doesn't sound good.
I'm not up on the 500 motors to say exactly what the problem is other than reading they have pins in the valve cover that the rockers are on, and those pins get sloppy over time with wear.
Have you had the valve cover off to inpect it or have you done work on it? If so, did you follow the service manual instructions? I've read of using rubber bands to hold the rockers in place so they don't get out of position while installing the cover.

I looked at your profile and posts to see if I could get some idea of how long you have had your bike and what you have done to it so far but you only posted about the B&B ignition(which you left hanging without any outcome). Where are you located(no location in your profile)? Someone might be close that knows how to help you with your bike, so put that in your profile.
Do you have the service manual for your bike?

Go to the new members section and introduce yourself and your bike, when and how you got it and it's history you know of it.
New member introductions
http://forums.sohc4.net/index.php/board,58.0.html

[RAFster122s]

Pull the end caps off the rocker cover and see if the rocker shafts have worn eccentric holes in the cover. That is a common issue on the 74-76 cb550 and I would presume it also affects the cb500 as the rocker cover is the same design.
That will tell you if your rocker shafts wear is causing issues. You cannot get a steady clearance as the shafts move and you can even get the rocker arm adjusters hitting the underside of the adjustment caps on the cover when it is bad.
77-78 cb550 pinned the rocker shafts so they don't wear the cover causing a problem...

[Andey108]

Thanks for the reply guys.

Oh the B&B was sorted… I ended up buying a new ignition box and that sorted out the problem…

But onto the next one which is this noise.

Not sure what RAF means about eccentric holes… I can definitely get those off and have a look, but not sure what I’m looking for…

I did use the rubber band method… wonder if the cover is warped?

Also I wonder if I mixed up the compression and exhaust stroke on the valve timing. Like it’s 360degrees backwards

[newday777]

Eccentric = out of round bushings, causes the rods to move when they should be stable.

[Andey108]

Eccentric = out of round bushings, causes the rods to move when they should be stable.

Got it, but in the cover itself or in the end caps?

Anything to do to solve it? New rocker cover?

[RAFster122s]

End caps
The shafts wallow out the cover into egg shaped holes, if the end of the shaft doesn't have equal spacing around it your cover has w
Excessive wear

[Andey108]

Hmmm doesn’t sound good. Sounds like that might be me.

I’ll check. Also could the rockers themselves be worn too? Anyway to check?

Question though, where in the timing chain should I install the valve cover?

Does it make a difference? I’ve taken it off 3 times, seems like it was easier one time than the other times.

[RAFster122s]

Hopefully you used the robber band trick to keep your rocker arms from contacting the valves when you reinstalled it. Otherwise, if you aren't careful you bend valves and or crack valve guides...

Don't understand your timing chain question.

Rocker shafts are surface hardened steel, cover is aluminum, unlikely you are going to have detectible wear on the shaft from the cover and usually negligible wear where rocker ride.

[Andey108]

Hopefully you used the robber band trick to keep your rocker arms from contacting the valves when you reinstalled it. Otherwise, if you aren't careful you bend valves and or crack valve guides...

Don't understand your timing chain question.

Rocker shafts are surface hardened steel, cover is aluminum, unlikely you are going to have detectible wear on the shaft from the cover and usually negligible wear where rocker ride.

Regarding the timing chain.

I meant is there any positions the lobes on the camshaft should be in when I install the cover? Just so there’s not a ton of pressure on the cam and springs?

One thing I did which seemed pretty stupid was to loosen all the rocker arm tappet screws to install the cover… seemed to help with installation, but it might have messed up the valve timing.

[seanbarney41]

Are you sure it is running on all 4 cylinders?  Does not sound like it to me

[Andey108]

Are you sure it is running on all 4 cylinders?  Does not sound like it to me

Yup all cylinders are firing…

Carb sync and temperature gun fired onto cylinder head and exhaust pipes for a 5mins check.

[seanbarney41]

When you look into the inspection covers after running is there a healthy amount of oil?  You can even take one off the exhaust side of the emgine while running and you should be able to see oil splash out.

[HondaMan]

What is your valve clearance? The intakes should be 0.002" and exhausts at 0.003". If they are more than 0.005" they clatter until the engine is revved up a little.

[Andey108]

When you look into the inspection covers after running is there a healthy amount of oil?  You can even take one off the exhaust side of the emgine while running and you should be able to see oil splash out.

Yup, checked with the tappet covers off.

Definitely oil in the valve spring area. Wiped clean, then seeing the oil return

[Andey108]

What is your valve clearance? The intakes should be 0.002" and exhausts at 0.003". If they are more than 0.005" they clatter until the engine is revved up a little.

That’s exactly the spec I used…

Checked 3 times in between starting the bike. Each time, checked twice before rotating the crank.

Might as well be super careful, doesn’t take too long each time (says that after 3 hours of measuring valve clearance…) lol

[craz1]

If your going to keep the bike I would locate a 77-78 cover which have the updated pinned shafts.

[Andey108]

If your going to keep the bike I would locate a 77-78 cover which have the updated pinned shafts.

Didn’t know they’re interchangeable.

77-78 is a 550 four engine?

[bryanj]

There is no position where the cam cover fits easy and loosening all the adjusters was not wrong for  a newbie wrencher just cos an experienced hand might not, there is a warning in the manual about lifting all ends of rockers when fitting cover, frequently called the rubber band trick!.
Things on 500 that  can rattle
Rocker shaft spindles in cover
Primary chain
Cam chain and tensioner
Clutch rattle, along with primary if carbs not 100%

Remember these are all old bikes now, nearly as old as me and that is OOOLD, so there will be wear  and tear

[RAFster122s]

77-78 cb550 cover fits cb500 and all cb550 top ends.
You can get the primary chain noise from worn chain and also if carbs have not been synced the primary chain and cam chain generate a lot more noise.
30k miles is around the number you would consider replacing the primary chain if you are in the motor for other work or find it has excess slack... Cam chain typically is a 30k mile item unless you are frequently adjusting then you can get more mileage out of them. Maintenance on the bike is important for longevity and well maintained and not abused riding styles generally yield longer life. But that isn't babying the motor as they like to rev, if you aren't seeing 5-7k frequently with a cb500/cb550 you are not enjoying it and riding it as it was designed...

[Andey108]

There is no position where the cam cover fits easy and loosening all the adjusters was not wrong for  a newbie wrencher just cos an experienced hand might not, there is a warning in the manual about lifting all ends of rockers when fitting cover, frequently called the rubber band trick!.
Things on 500 that  can rattle
Rocker shaft spindles in cover
Primary chain
Cam chain and tensioner
Clutch rattle, along with primary if carbs not 100%

Remember these are all old bikes now, nearly as old as me and that is OOOLD, so there will be wear  and tear

So just torque it down equally in the normal bolt pattern is fine?

And the rubber band trick is bad? I’ve never seen that warning.

[scottly]

It sort of sounds like an exhaust leak? A good test is to use a length of tubing, holding one end next to your ear, and probing around with the other end.

[Andey108]

It sort of sounds like an exhaust leak? A good test is to use a length of tubing, holding one end next to your ear, and probing around with the other end.

Shouldn’t be, can feel any air escaping from that area with a basic smoke test.

Exhaust gaskets are new with exhaust paste.

[Sdsbassist]

Have you messed with your exhaust at all?

Sent from my SM-N960U using Tapatalk

[bryanj]

Rubber band trick is good not bad, you use to hold theadjuster ends of the rocker arms up by connecting the arms on each cylinder with them