Topic: CB550F "heartbeat" diagnosis

[mgzych]

I'm new to the old bike scene.  I'm happy to have found myself a '75 CB550F that is very much a runner.  Two things have my attention, though.  I'd appreciate any diagnoses of these "issues," what effect they may be having on the bike's proper performance, and whether they're cause for concern as far as the longevity of the engine goes.

The first is that the choke seems to have no effect on the way the engine runs, and to start it, I have to turn the idle up a turn or more, and then after the engine warms up and the revs pick up, turn it back down.

The second is a pair of noises that come from the running engine.  You can hear them in the attached video, though they sound a little different and more pronounced in person. One is a continuous rattling sound.  Hear it?  The other is a more rhythmic "clacking" sound that actually has a more "metallic" tone to it in person.  Is that just the exhaust note, or is this sound something different from within?

Thanks for any and all thoughts.

Mark

[mystic_1]

I'd bet a dollar on:

Continuous rattle = loose cam chain
Metallic clacking = excessive valve lash

These are both standard tune-up items.

RTFM and get 'er done!   

mystic_1

[mgzych]

Alright. That sounds straight-forward enough. Time to get my hands dirty.

[scunny]

+1 on mystics mention of a full maintenance, then see what you have.

[flatlander]

what the other have said.

not wantint to scare you but in case you don't seem to be able to adjust valve leash and keep hearing a clicking sound: honda changed the design of the rocker cover during the production of the 550f. in the earlier design the rocker shafts could turn with the rockers and wear out their seats. in later models this was fixed. your bike being from 1975, it would have the earlier type if the cover was not changed at some point.
if you have an older type cover and it's still good you can buy an extra set of o-rings like the ones on the end caps of the same cover to replace the existing ones, and jam the old ones into the holes where the rocker shafts are. apparently this will keep them in place.
if your cover is worn then the easiest fix is to find another one of the newer type.

see also here http://forums.sohc4.net/index.php?topic=122627.0 and here http://forums.sohc4.net/index.php?topic=131933.0

[calj737]

I'd offer another perspective: it does not sound to me as though the carbs have been vacuum synched. It does appear that at idle, you're almost running on a "missing cylinder". Check each exhaust pipe with a spray of water to insure they're all equally hot (the water should evaporate quickly after 20-30 seconds of running).

Carbs that are not synched while produce pretty good rattling noises within the engine, even low "clunk" sound. The cam chain is also certainly in need of attention, but do start or at least perform, a carb synch on any bike you buy. It's not often done by at home bike owners, but it needs to be done. (This may also address your frequent idle adjustment issue).

Great looking bike!

[Bailgang]

+1 to all the above. Out of sync carbs can make you're engine sound like it's falling apart at idle depending on how out of sync they are but I would recommend you make sure the cam chain tensioner is set correctly and set your valve lash first then sync the carbs last. My 75 cb550 was a noisy old girl especially when cold and I even put in a new primary chain which did help but but most of the noise mine had was due to the sloppy old style valve cover that flatlander mentioned. As far as messing with idle speed when starting it cold to the point it's at operating temp is something you probably will just have to deal with. Properly synced carbs help but the reason you may still need to mess with it is because the choke on yours doesn't have a high idle speed screw in the choke mechanism like say my 77 750 does.

[flatlander]

do you have the honda manual for your bike? you can find it here http://www.sohc4.net/cb550books/ or here http://www.honda4fun.com/materiale-documentazione-tecnica/libretti-uso-a-manutenzione (site is in italian but the manuals are english)

then go through the whole maintenance schedule, or at least the 3000 miles tune-up. that should sort out the basics, incl. the stuff mentioned above.

[Scott S]

 Carbs that are out of synch will make these Honda's sound like $h!t.
 Do the full tune up and vacuum synch the carbs. It really, truly does make a HUGE difference.

 I've owned several 500/550's. They all vary on whether or not they like choke. Some need full choke, some almost none at all. It's all part of "getting to know" your bike.

[mystic_1]

Just wanted to point out that you should adjust the cam chain and the valve lash (and also ignition timing) before doing the carb sync.  If you don't do it in this order, you'll get inconsistent results

Replace your air filter and spark plugs with new, also, before you start.  Do the air filter even if you think it "looks clean".  Gap the plugs, don't assume they're pre-gapped.

mystic_1

[Stev-o]

+1. Do the full 3000 mile tune up recommended by Honda.  You have a nice steady idle, that's good, how does it run out on the road?

[mgzych]

Thanks for all the feedback/ guidance.

Aside from checking/correcting possible wearing of the valve rocker shafts (and routine oil change), is there any urgency in making any of these adjustments? I'm thinking in terms of undue wear and tear to the engine.

It runs consistently once it's warmed up. Not quite as much "spring in her step" as I might have hoped for, but I don't have a lot to compare it to, and I still enjoy the hell out of the ride!  Seems to be a little weaker between 5k and 6k RPM.  I suppose a proper tuning would eek a little more out of the engine.

From a ride perspective, the front end seems a little jittery.  Nothing alarming, but not completely confidence inspiring either. I'm curious about adjustments to the front forks.

BTW, do you guys have any favorite parts/supply houses for the tune-up and maintenance type items?  Brands?  How about tools--the essentials and what brands/stores are favored and/or offer good value?  (I don't have much of a selection to start with.)  Maybe this should be for another thread...

Thanks again!

Mark

[calj737]

Well the 3.000 tune up would have you check the front end bearings, fork oil, and carb adjustments, valve adjustments, ignition timing and cam chain tension. Do all these things as previously suggested and you'll likely encounter evey bit of maintenance issues with your ride.

All these items are intended to prolong the life of the bike and rider (safety issues). Can't make it any clearer than that for a priority.

[BobbyR]

The jittery front end should be addressed now.  If your engine craps out you are stuck on the side of the road in a pissed off mood.
If you have suspension failure you can wind up on the ground.

Check your tires. They last about 5-6 years no matter how good they look! This is no bull#$%*!

You can continue riding while doing most adjustments.

Drain the oil out of the forks and replace it. Rotate the wheel and also see if it has bearing wear. You may want to flush out the brakes while you are there.

Valves can be adjusted in an hour another day.

Synching the carbs comes after valve adjustment, it is another. hour or so another day.

I did a rolling restoration/repair doing things when I had time. Some tear down the bike and do everything in one shot. In the end it comes out the same way.

The later CBs had a fast idle cam on the choke, before that you just used the throttle to keep the idle speed up till she warmed up. Turning the idle screw up and down can be a pain and you also lose your engine braking.

Safety items first and then quality of ride issues can work out very well.


   

[flatlander]

exactly what cal and bobby say. in addition, check your fork springs as they may have sagged after almost 40 years.
if necessary, with new springs, oil and seals your forks will be back in good shape (i'd also advise you to upgrade conical headset bearings if you are replacing them).

then you'll know what honda intended the frontend to be like. if you still need more after that, you can add a fork brace (much recommended!), progressive springs of correct rate, emulators if you need/want, and the right weight oil for you.

"rolling restoration" as bobby calls it was what i did as well - one bit at a time starting with the safety relevant stuff.

[Deltarider]

, and to start it, I have to turn the idle up a turn or more, and then after the engine warms up and the revs pick up, turn it back down

That's normal. Are you sure yours is idling @ a true 1100-1200 rpm. I'd say it runs a bit low.
First address all aspects of the ignition and make sure gas reaches all 4 carbs. I cannot stress this enough. In the FAQ you'll find the best way to adjust camchain tension. Are you good in checking and setting the valves? If not, have an experienced friend look over your shoulder.
Carb syncing is an all time favourite on this site. People can't wait to bring out their new tool and do it, even if the uneven idle originates elsewhere. Don't be mislead! If syncing is never been done by a PO (very likely unless it's a member of this site), chances are good your carbs don't need syncing. Yes, you read well. (Nevertheless people will call me names. Just wait and see.) Fact is that Honda, after learning from the first model 750 that had the carbs operated by four cables, did a very good job with the desmodromic design we have. Ofcourse it's good to check the sync as described in the maintenance list, after you did the rest of the maintenance, but think twice before you start adjusting. In the experience of many old (and wise) CB owners a rough idle has more often it's origin elsewhere.

honda changed the design of the rocker cover during the production of the 550f. in the earlier design the rocker shafts could turn with the rockers and wear out their seats. in later models this was fixed. your bike being from 1975, it would have the earlier type if the cover was not changed at some point.

From engine number 1133172 Honda modified the rocker cover. From then just four shafts instead of the 8 on the older models up to engine number 1133171. If you're interested have a look in the various Parts Lists. You'll find them all here: http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb550

[Rgconner]

Check the choke position very carefully.

On my 75, it is reverse of what you expect, the lever is 90 off alignment as designed.

Vertical position means choke is open, horizontal means it is closed.

[mgzych]

"Rolling restoration" it will be, although I hope it's more of just a "rolling fine-tune."

I thought I was going to go at the engine first, but it sounds like the consensus is the front end is more important. For clarity, though, when I said the front end was jittery, I meant that it is just a bit of a stiff and rough ride with respect to the suspension.  No slop in it from what I can tell.  How do I tell if the springs warrant replacement/upgrade?

I noticed the manual's supplement on sohc4.net re: valve cover rocket shafts and checked my engine SN. I've got the original version, so I'll have to check for play there.

Interesting about the choke lever. I'll check it, though I don't know if it'll matter since it seems to have zero effect either way.


Any tools and parts purchase advice?

Thanks,
Mark

[Stev-o]

Start with a basic hand tool set: metric wrenches and socket set.  JIS screwdrivers are very good, an impact driver and hammer are a must.  I like Craftsman tools, good value for the money and excellent warranty.