Topic: CB 550 clunky idle - NEW TURN OF EVENTS!

[Franky]

Hi guys

My 1976 CB550 K has over some months gone from a quite smooth idle and general smooth running of the engine, to a more clunky idle/running.
The clunks are erratic and not rythmic. One can almost feel the clunks as you sit on the bike - especially when the engine is cold. It seems to be more than the 'usual cam-chain rattle'... or is it? The fact that it went from quite smooth to clunky bothers me and tells me that it is not just regular rattling.

I'm still somewhat of a novice in this field, so please lend me your ears and experience.

Here's some info:

- Stock engine except for pods.
- Small 3 amp battery, kick only (starts 1st kick - even when cold.)
- Did a carb sync with a proper tool with 4 gauges - All good.
- Adjusted the ignition timing. It was a little off, but just in a regular maintenance way.
- Did some top-end work last year. Swapped the head from my parts bike that was in better conditon than the org. one. Same with the cam chain tensioner. When turning the adjuster-screw, everything did rotate as it should (when just holding the piece, before installing it.)
- Both before and after the top-end work, I have never gotten the cam chain tensioner to do as the manual says (and here: http:www.franky.dk/Honda/CB550_cam_chain_adjust.pdf). If I turn the screw anti-clockwise, it never rotates back (clockwise), and I can only turn it 1/4 or so.

I have uploaded two videos on Youtube - one with the engine cold (8 deg. celcius) and one after having ridden for half an hour or so. In the cold video, I'm using varying amounts of choke and let it die at the end (ie. not keeping it alive by turning the throttle). Never mind the salt and rust - I ride it now and then in the horrific danish winters :-)

Cold engine idle video: http://youtu.be/HODSvj8DBm0
Warm engine idle video: http://youtu.be/y2HqyMwu-8Y

Any comments on this subject or whatever else you may be able to tell from the videos are greatly appreciated.
 

[flybox1]

sounds pretty good for a 37+ year old engine. 
IIWM, id recheck my valve lash and set the cam chain, by the book.
if those, and a good vacuum sync dont quiet it down, id ride and enjoy it as-is.

[wjustinleigh]

It's clearly the pods!  (kidding)  You might try some ethanol treatment in the gas, I went through a spell of something like that on a trip on my cb750 and it cleared it up.  I'm sure people on here will have a lot more knowledge than I do on gas issues but I was running it on the high octane stuff.  It apparently sits around longer because people don't buy it as often (especially on the back roads of Washington) and the ethanol absorbs water, resulting in an unhappy engine.  I switched to the middle grade and started adding a cap full of ethanol fixer and it was back to normal.

The high idle sounds pretty good to me, if I could get my cb500 there I'd be pretty happy.  Mine needs to take a little extra time with the choke on this time of year to get a decent low idle.

What's that little speedometer you have on there?

[Franky]

wjustinleigh: The speedo is a weatherproof Sigma bicycle speedo that go up to 199 km/h (or miles i guess). Because of my fork-swap there is no room for a a regular speedo and I actually like that it's so small.

Here some info and pics: http://forums.sohc4.net/index.php?topic=118983.msg1433623#msg1433623 and http://forums.sohc4.net/index.php?topic=118983.msg1450119#msg1450119 (scroll down a bit)

And well, yes, I guess the engine sounds quite good in the 'warn engine' video. The clunkiness is hard to tell. I'll try and see if I can capture it in another video. It has just never been that clunky before...

[Maurice]

Doesn't sound bad to me. Is it the same with the clutch pulled in? If anything cold there seems to be some cam chain noise. That one can seem random while it gets oiled.

[dave500]

dont let it idle low when its cold,hold a fast idle,have the carbs been synced lately?

[Franky]

Dave: I synced the carbs about a month ago with a proper tool - 4 pressure gauges and all that. Adjusted one cylinder slightly, but it was not far off - maybe 5-10%.
And no, I usually don't let it idle that low - it was just to exaggerate the clunky sounds!

How does one know if the cam chain is stretched/worn or when the tensioner unit need replacement? Is it normal that the tensioner screw doesn't spring back when turned anti-clockwise?

[TwoTired]

Do a compression or leak down test.  Want to idle smooth?   They must all be have the same numbers.

Install new plugs or at least look at the plugs you have now to observe the combustion deposit patterns.  Spark variation= uneven idle.

Why doesn't the choke boost the idle RPM when cold.  With PD carbs, it should.
It will never idle cold like a fuel injected and computerized engine.  The Carbs are too dumb to adjust the idle mixture automatically.  That is what the choke and your brain is for.
The intake popping I heard when cold is likely because the mixture is too lean, or the valves are not seating reliably or completely.

A smooth idle requires a recent 3K tuneup completion, and each individual filter providing the same pressure drop as the others.


What are the carb settings?
Pilot screws, main jet size, pilot jet size, slide needle?
Are the floats keeping the fuel level in each carb the same?



My condolences regarding only being able to afford the cheapest pods you can find.

[Deltarider]

And no, I usually don't let it idle that low - it was just to exaggerate the clunky sounds!

Well, there's your answer. All 500/550s do that when they idle low. Make sure your engine doesn't idle below 1100 TRUE rpm and you'll be fine. Personally I have the impression your engine runs fine.

[Bailgang]

And no, I usually don't let it idle that low - it was just to exaggerate the clunky sounds!

Well, there's your answer. All 500/550s do that when they idle low. Make sure your engine doesn't idle below 1100 TRUE rpm and you'll be fine. Personally I have the impression your engine runs fine.

+1
My 550 was a clatter box when cold if I didn't bring the idle up yet was smooth as can be when fully warmed up.

[Duanob]

Sounds fine (or normal) to me just bump the idle up until it sounds smooth. Mine runs about 1300 usually. I figure on an engine that goes to 9200RPMs, a couple of hundred RPMs is nothing.

But yes as TT says do a 3000 mile tune up first and foremost. Then on to the carbs.

[strynboen]

as you can hear..is mine not komplet free for ticking saunds..this is normal for old bikes..mine has gone 75,000 km

honda cb 550 k3 1978

[Franky]

Thanks to all of you for your advice. Also thanks twotired, for chiming in - as a dane I can appreciate the sarcastic remark about the pods :-) They were actually in place when I got it, and was running fine back then - sans clunks!  The clunkiness is more apparent at idle, but I also feel it somewhat when riding at higher RPMs... This issue is not just about a smooth idle.

I think I will start out with a more thorough 3K tune-up and then look at float level and, compare the carb settings, jet sizes to some of the "this-is-what-I-found-works-well-with-pods" guides/descriptions found on the site. If this doesn't bring any major improvements, I will report back.

Apart from that, I am wondering if anyone has an answer to these questions:

How does one know if the cam chain is stretched/worn or when the tensioner unit need replacement? Is it normal that the tensioner screw doesn't spring back when turned anti-clockwise?

By the way:
As far as I've been able to search, the 3000 mile tune-up consists of the following:
1. Compression test
2. Cam chain adj.
3. Valve adj.
4. Spark plugs clean & adj.
5.Condenser
6. points
7. timing
8. Air filter
9. Carbs

[strynboen]

if that senter schrev..not spring back..even the kontra lock bolt are loose??...can the tredden senter be turned more raunds??..it MUST only be turned 1/4..if more it break loose...adjusting must be done witaut turn that..by loosing the kontra bolt..and get the cam stand so the chain are slock,,,the inbuild spring vill automatic adjust the tensioner bar..so dont care abaut the senter schrev...you can pusk pull it a few milimeters in aut..to be shure it not are stuck

but get a photo of the tensione bar...to get a idea of funktion..i faund a you tube video ...but.. cant find it now

edit.... read you have it apart...so you have seen the parts live..

[Franky]

It's been a while since this thread was alive, but I finally got on with it. After performing the 3000 mile tune-up I did experience an improvement, but not to the extent I was hoping.

Then I had a look at the primary chain... Oh boy! It's very loose. I can easily pry a screwdriver inbetween the chain and the gear! There's quite a bit of sideways play and it has been rubbing against the side of the cases. I take it, that this is most likely the primary cause of the rattling and clunkyness?

Now, from what I can read from other posts, this means splitting the cases to replace the chain.

What would you suggest I should look at/replace/fix now that I am in there?  Damper rubbers (primary gear)? Cam chain? Oil pump or oil pump seals? What else?