Topic: 1978 CB550F issues any help greatly appreciated

[iancb550]

Hi all, I recently bought a 1978 CB550 and I have discovered some issues with it and I wondered if anyone had any ideas on what to check for / how to fix them at all: -

1st I have noticed some tiny bubbles and a little bit of a leak around the head gasket on the right side when the bike is running, they seem to go away once it is warmer and I guess things have expanded, will this need to be replaced?

2nd Performance is not great, it really struggles quite a bit to get to 70 mph yet it sounds fine and revs freely, rides up to 50 / 60 mph it seems happy.

3rd I seem to get a fair delay in the throttle response and sometimes a dip before the power kicks in when putting a fair amount of throttle on.

I checked that it was firing on all cylinders and everything seems ok in that respect at least.

I've had a twin for the last few years and before that a V4 so not really much experience at all with the older straight 4s. Thanks a lot in advance for any advice on what to do or check for.

[Pat_at_APE]

Hello Ian,

I've got a 77 CB550F that I have not had very long. 

Regarding your head gasket issue I would first try to loosen and re-torque the head stud nuts to the factory spec and see if that solves your issue.  If it's been going on for a long time the gasket may be toast and must then be replaced. 

I've got similar performance issues with my bike that I have not had time to research.  I hope one of the sages gives you some good advise on what to check and how because I'll we watching as well. 

Cheers,
Pat

[iancb550]

Hi Pat, good to know at least someone else has the same issues. I am wondering if that is just the way the bike performs in general, I think I need to let someone who knows how a perfect working example performs ride it, so they can judge.

Also thanks for the advice on re-torquing it, hopefully that will help seal properly. Would a small leak like that have any effect on the performance do you think? The bike starts fairly easily with the choke on and idles happily at about 1,500 rpm there is a slight, very slight rattle sound to it but that could be it's normal running sound as I have not heard any other CB550s before.

[iancb550]

Just as an example Pat, I saw this video 1977 Honda CB550F top speed. mine is no where near, not even close to that fast, is yours?

[iancb550]

Could the timing advancer or condition of the plugs cause this kind of big drop off in performance? I was told the plugs had been changed just before I bought it but I will check them and find out.

Also when torquing up the head stud nuts, do they need to be done in order? I have only seen the order for loosening is: -

In x's starting at the inside - top left (center), bottom right (center), Bottom left (center), top right (center), then the next group.

Is it the opposite for tightening?

[lucky]

Hello Ian,

I've got a 77 CB550F that I have not had very long. 

Regarding your head gasket issue I would first try to loosen and re-torque the head stud nuts to the factory spec and see if that solves your issue.  If it's been going on for a long time the gasket may be toast and must then be replaced. 

I've got similar performance issues with my bike that I have not had time to research.  I hope one of the sages gives you some good advise on what to check and how because I'll we watching as well. 

Cheers,
Pat

Do not loosen the head bolts.
To loosen ALL of them you would have to remove the engine from the frame.
If you can remove the valve cover while the engine is in the frame on the "F" model then you could re torque all of the head bolts except the middle two bolts.
You would have to remove the cam towers to get to two of those bolts.

It has been my experience that re torquing head bolts will not fix a leaking
head gasket.

The most important fact is that you did not tell us how many miles are on the engine. You said you have had the bike for a very long time. What does that mean?

One thing you need to check is that the accelerator pump nozzles are working on the carbs.
Remove the airbox and with the engine off and carb float bowls full of gas turn the throttle and make sure all 4 brass jets in the venture's are squirting fuel.
They could be clogged. The accelerator pump system was added just to cure the hesitation problem, so if it IS hesitating the nozzles may not be getting gas.

I feel that this is more important than the head gasket problem because it
could be running lean. Running lean can overheat the cylinder head and make it leak by becoming unevenly heated.
See what I mean?

Use a bright light.

[iancb550]

Hi lucky thanks for the reply there are just over 21,000 miles on the engine. I bought the bike earlier this week privately having not had much experience with this model of bike before, it seemed to accelerate reasonably in the kind of roads I was able to test ride it in.

I do get the feeling it had not been used for a while, but the previous owner told me they had given it a basic service. I guess that would not really include un-gumming any jets.

That uneven heating could explain why the head gasket is leaking a little only on one side. I will try to follow those instructions and see of the jets are working hopefully I can find them

[Tews19]

If you just bought the bike. Do the 3k tune-up.... When you reach 60-70 miles does it seem to bog down? i had this problem for a little while on my 550K. I ended up checking all the spark plug caps and one was not on all the way. I trimmed the wire, reattached the cap and I also cleaned the carbs. Bike runs like a top now... But definately do a 3k tune-up.

[Rgconner]

You should be able to get to those bolts without removing the engine from the frame.

Heck, you can tear them down to the case while still in the frame.

However, I would definitely get some of the "pucks"/"rubber nickles" under the valve cover, they keep oil off the head nuts. Also a valve cover gasket.

Personally, I would run it a bit, change the oil, etc. It might take care of itself as the bike gets back into running condition.

Also, how much leakage can I stand? is a question you should ask your self. These bikes do tend to weep a bit.

[iancb550]

Cheers all, the little bit of leakage is ok with me, I am quite worried about the jets being blocked though and generally running lean, or the accelerator pump that was mentioned earlier because I am getting that lag. Also the general performance is really rather bad , I really have to give it almost full throttle to even push it up to 70 and it's at about 7k rpm when it does get there.

As I have a really poor knowledge of bikes mechanically I am wondering if I should just take it to my local mechanic to get these jets / nozzles cleaned then hopefully start from there, as I was going to try and learn how to do all the maintenance on it myself but I don't want to run it like it is if it's going to damage it or make the head gasket problem even worse. Also I think with the speeds cars get up to on the roads here it wouldn't be safe with the kind of acceleration I am getting.

Then when I know it is at least performing normally I can do a general service myself and follow the manual for the other checks and adjustments. Maybe I will be able to attempt the head gasket change but it might have to go to the mechanic for that too.

[iancb550]

But I will also check those plug cables as I was told he had recently changed them, maybe one was not properly attached but I do feel that is hopeful thinking on my behalf As all of the pipes are hot I believe all the cylinders are firing.

[Gordon]

You should be able to get to those bolts without removing the engine from the frame.

Heck, you can tear them down to the case while still in the frame.

+1

Just to help clear up any confusion.  Whether or not you intend to re-torque the head, all top end work can be done on all of the sohc4's with the engine in the frame with the exception of the 750.   

[luap]

I would imagine you would leak more oil when the motor is hot. oil becomes thinner hotter it gets. at idle the oil will drip at speed the oil will fly, is there any sign of oil above the head gasket? I would start with the tappet cover mentioned below the rocker shaft covers,
if its around the base gasket might see if the chain tensioner 10mm bolt is tight

[iancb550]

I can just see some tiny air bubbles escaping it seems from the head gasket, hopefully that's the right term for the gasket about two thirds of the way up the cooling fins. That is when I first start it, then if I ride somewhere get off and look at the same place it seems to have stopped.

Do you think the cleaning of the jets and the nozzles for the accelerator pump is something I could do with very little experience of ever working on a bike before or should I take it to the mechanic?

[ZanVooden]

Have you checked the timing and point gaps?
Pull the spark plugs and make sure they are clean and in good condition and set the gap.
Is the fuel fresh?
Check the accel. pump.
Have you check the air filter?

This is a new bike to you so its best to just start with doing all the general maintenance items.

[iancb550]

I haven't checked those yet, I will go through each of them using my workshop manual, though its just a downloaded one rather than a haynes etc It doesn't describe the checking of the accelerator nozzles though, hopefully I can do that from the instructions earlier but may very well need to ask for help again as i've never seen them before.

[iancb550]

thanks for all the advice so far, will work through these steps and get back to you and if all else fails book it in to get it's jets properly cleaned I think.

[TwoTired]

Hi all, I recently bought a 1978 CB550

Your thread title says F model, yet Honda only offered the K model in 78.  ??  F models were only offered in 75-77

There's a lot different between them.  Hard to specify a proper approach without knowing more AND if the air induction and exhaust are still stock.  These latter changes often destroy the nice operation of this bike.

...and I have discovered some issues with it and I wondered if anyone had any ideas on what to check for / how to fix them at all: -

1st I have noticed some tiny bubbles and a little bit of a leak around the head gasket on the right side when the bike is running, they seem to go away once it is warmer and I guess things have expanded, will this need to be replaced?

This is quite common and is normally the small oring that seals the oil passage going to the cam area.  It is NOT the head gasket.  Although the o ring is on the same surface as the head gasket.
A re-torque will do nothing for a hardened and shrunken oring.  And, over torquing can snap a cylinder stud.  The cam cover/cylinder cover must be removed to do that anyway.  Further, if you don't put the cam cover back on correctly it is very easy to bend valves which creates far more costly and time consuming problems to solve.

If you are anal about having the engine totally oil tight, then you have little choice but to replace the entire top end gasket set including the cylinder base gasket, which means pulling the cylinder block off the pistons.  It's not a task for the inexperienced.

I have several 550s and most of them "weep" a bit of oil at the end of the cylinder block.  The engines run too good to take them apart for such a minor inconvenience, so I just wipe them off periodically. Some have reported that fresh oil and bit of run time slows the weep down or stops it.  Some oils have additives to keep orings soft and pliable.

2nd Performance is not great, it really struggles quite a bit to get to 70 mph yet it sounds fine and revs freely, rides up to 50 / 60 mph it seems happy.

It does sound like you have cylinder cutting out.  Have you checked for even heap pipe heat?
But, beyond that, the routine 3000 mile tune up check list should be performed before any other corrective action is taken.
Plugs, points, timing, cam chain adjust, tappet clearances, and air filter should all be renewed if you don't know their definite history.
A compression test is nice to have, if for no other reason than future reference.

3rd I seem to get a fair delay in the throttle response and sometimes a dip before the power kicks in when putting a fair amount of throttle on.

This could be due to exhaust and air filter issues, or unreasonable expectations on your part.  550 carbs (either style) have no accelerator pumps.  When you open the throttle there is a sudden volume increase in inlet air, but, also the vacuum level falls which is what is pulling the fuel through metering jets, hence the wheeze/stumble from a too lean A/F mixture.  For this reason, the pilot circuit is adjusted over rich at idle position.  A filter or exhaust change (for the 78) can make the pilot circuit lean, and exacerbate the issue.  Normally you can: in any gear snap the throttle up to 1/2 of total available travel and get a smooth and reliable pick up of engine RPM.  Of course higher gear won't be too quick from low RPM.  But, it should do it without complaint.
This is the nature of this carb style and the engines need for RPM to make power (Note the high red line on the tach?)

I checked that it was firing on all cylinders and everything seems ok in that respect at least.

Please confirm with the head pipe heat test.  But, I have had a 550 where one carb went too rich above about 4000 RPM and failed a cylinder at speed.  The carb bodies were corroded inside.

You might check the a ignition advance sytem is operating correctly.
And a report of what the spark plug deposits are for each cylinder would also help us.

Cheers,

[Rgconner]

Some have reported that fresh oil and bit of run time slows the weep down or stops it.  Some oils have additives to keep orings soft and pliable.

Just a small clarification: Don't EVER EVER EVER put anything in your oil that promises to fix oil leaks.

EVER!

You have a wet sump, the additives will swell the clutch plates and then you are in for a new set.

Oil for these bike should also never contain "slip modifiers" either, it will make the clutch slippery too.

(OTOH, that was one of the things that made my bike cheap, the Prev. Owner had put regular oil in it and it slipped like crazy under load and shifted like crap)

The only additive you want in the oil is anti-shear/anti-foam additives that are found in Diesel engine oils like Shell Rotella and Mobile Delvac. Get it at Walmart by the gallon, in 10w-30 or 15w-40 depending on your temps.

 (probably 10-30 unless it gets over 100 degrees where you are. Wait, are you in the UK? maybe no Wal-mart. Whatever is the equiv. Tesco?)

Try a few brands. Sometimes a bike shifts better with different oils. I suspect wear and condition is why, or it might be just what the rider "likes" it feel like.

 

[Danno]

sounds like classic pods problems to me and it is running lean at mid range to wot

[TwoTired]

Some have reported that fresh oil and bit of run time slows the weep down or stops it.  Some oils have additives to keep orings soft and pliable.

Just a small clarification: Don't EVER EVER EVER put anything in your oil that promises to fix oil leaks.

EVER!

You have a wet sump, the additives will swell the clutch plates and then you are in for a new set.

Oil for these bike should also never contain "slip modifiers" either, it will make the clutch slippery too.

(OTOH, that was one of the things that made my bike cheap, the Prev. Owner had put regular oil in it and it slipped like crazy under load and shifted like crap)

The only additive you want in the oil is anti-shear/anti-foam additives that are found in Diesel engine oils like Shell Rotella and Mobile Delvac. Get it at Walmart by the gallon, in 10w-30 or 15w-40 depending on your temps.

 (probably 10-30 unless it gets over 100 degrees where you are. Wait, are you in the UK? maybe no Wal-mart. Whatever is the equiv. Tesco?)

Try a few brands. Sometimes a bike shifts better with different oils. I suspect wear and condition is why, or it might be just what the rider "likes" it feel like.

I don't think you can buy an engine oil today that doesn't have an additive package, not that they will tell you what's in the additive package blended with their oil.  I agree you don't want an automotive "stop-leak" product added to the oil.

As a start, you *could* use what Honda recommends in the owners manual, which is 10W-40.  As a baseline, do the first change with Honda oil, GN-4 or HP-4.  You can't go wrong with those.  Experiment later after you've noted the engine, clutch, and trans characteristics with the approved and recommended baseline.  Then go for the cheaper stuff or a viscosity variance change and see how it goes.  But, I gotta say it may be false economy to go with cheapest oils, as repair parts and down time inconvenience rather offset the savings of cheap oils.  My 550's love Honda's HP-4.  It shows in the smoother shifting.  I've used other oils that do as well.  Some keep the smoothness longer than others.  That and the oil appearance tell me when it's time for renewal.  Maybe it's just me.  But, I'll pay a bit more for oil if it keeps me from taking the engine apart and replacing bits.

Jeez, we've degraded to an "oil thread".    

Cheers,

[iancb550]

Many thanks again to all who are contributing to this thread. The test I carried out to check the cylinders were all firing was to just start the bike then touch lightly each of the exhaust pipes and each was very hot to the touch fairly quickly after starting.

Is it only the CB550F that is the super sport? It has the 4 into one exhausts, it could be that it was a 77 registered in 78 ? It has a short 5 digit number plate so it is a bit hard to check at a glance the year, but when I sent it's plate off for a check it said it was registered in Feb 78.

This is an image of it if it helps to identify it's exact model? http://iansramblings.com/wp-content/uploads/2012/01/Honda.jpg

I am fine with the small weap of oil and with the throttle lag as I have experienced this before on the NC30 (though that was more of a delay than a dip and surge). The problems with the performance in general is what was causing me to apply more throttle in that circumstance to try to get up to the speed of the road I was on.

I have 10 40 putoline oil for it at the moment, so just incase the previous owner didn't use the correct oil I will dump the current oil and then re-do the job I think. I will also try and run through all the other items listed earlier for a 3k service and then at least I have level playing field from which to start.

The thing I am most worried about is whether all or some of the jets are slightly blocked making it run lean on some or all of the cylinders.

[Rgconner]

Very likely a 77 in 78.

Does it have accelerator pumps and CV carbs? I think that appears on the 78 for emissions.

 

Jeez, we've degraded to an "oil thread".    

True, but the oil in these machines is much more than just a lubricant. As you know, it can really change the nature of the shifting and clutching on these bikes.

I put the Honda oil in, it clutched fine, but hard to find neutral. Mobile Delvac is what makes my bike shift the best, never a problem finding neutral. 
And you can't go wrong with it, it might be inexpensive, but it is not cheap.

Milpitas is my home town, so I know the average summer temps are 20 to 30 lower than Sacramento. I like the extra protection of the 15-40.

[HondaMan]

Some have reported that fresh oil and bit of run time slows the weep down or stops it.  Some oils have additives to keep orings soft and pliable.

Just a small clarification: Don't EVER EVER EVER put anything in your oil that promises to fix oil leaks.

EVER!

You have a wet sump, the additives will swell the clutch plates and then you are in for a new set.

Oil for these bike should also never contain "slip modifiers" either, it will make the clutch slippery too.

(OTOH, that was one of the things that made my bike cheap, the Prev. Owner had put regular oil in it and it slipped like crazy under load and shifted like crap)

The only additive you want in the oil is anti-shear/anti-foam additives that are found in Diesel engine oils like Shell Rotella and Mobile Delvac. Get it at Walmart by the gallon, in 10w-30 or 15w-40 depending on your temps.

 (probably 10-30 unless it gets over 100 degrees where you are. Wait, are you in the UK? maybe no Wal-mart. Whatever is the equiv. Tesco?)

Try a few brands. Sometimes a bike shifts better with different oils. I suspect wear and condition is why, or it might be just what the rider "likes" it feel like.

 

One word of advice: NEVER run 10w30 oil in these bikes. It is simply not heavy enough. At the minimum, and on cool/cold days only, you can run 10w40. Honda used that number on their dipsticks as a warning to never run lighter oil than that. Use 20w50 in summer, 20w40 in Spring/Fall if you wish, or 15w40, and save the 10w40 for the cold weather riding. If you use 10w30, you will soon have worn bearings and valve guides, provided the clutch does not burn first.

[TwoTired]

Many thanks again to all who are contributing to this thread. The test I carried out to check the cylinders were all firing was to just start the bike then touch lightly each of the exhaust pipes and each was very hot to the touch fairly quickly after starting.

Due to the nature of mechanical slide carbs, the pilots provide nearly all the fuel at idle and the mains and Throttle Valve circuit is a separate path for fuel mixture delivery.  Checking for head pipe heat at idle is simple, checking for mixture/head pipe heat at the 1/2 and higher throttle positions is a bit trickier. (But, read on you may not need to do that.)

Is it only the CB550F that is the super sport? It has the 4 into one exhausts, it could be that it was a 77 registered in 78 ? It has a short 5 digit number plate so it is a bit hard to check at a glance the year, but when I sent it's plate off for a check it said it was registered in Feb 78.

This is an image of it if it helps to identify it's exact model? http://iansramblings.com/wp-content/uploads/2012/01/Honda.jpg

That would be the 77 model in the states, which it should be labeled as such right on the VIN plate and it is definitely The F model.  (My fave)  Which is the Super sport.  There are differences in export models outside the states.

The thing I am most worried about is whether all or some of the jets are slightly blocked making it run lean on some or all of the cylinders.

The exhaust system on your bike is not stock, but rather aftermarket items.  The exhaust was probably made for the more populous K model, which has a different carb set up.
The carbs almost certainly need rejetting to compensate for the pipe and muffler change, and is no doubt why it falls flat at higher speeds.
The slide needles must be raised two clip positions.  Stock F is in the 2nd clip position from top on the needle, and K is 4th pos. from the top of the needle.  Further, the main jets should go from #98 for the F pipe to the #100 that all the K models used with the early style carbs, stock air filter and exhaust.

The slides need to be removed to change the jet needle position. It can be done without removing the carbs from the bike as can the main jet change (being double jointed helps, as well and a good assortment of tools).  However, the carbs will need a vacuum sync after the slide disturbance.
You'll want to do all the tune up list before vacuum syncing the carbs.

With the above changes you could also move to the UNI NU-4055 filter element, which will save some money in the long run.

If the carbs have not been changed from stock settings, the bike almost certainly is running lean at the higher throttle positions.  A look at the spark plugs would confirm, they'll be white or very light tan after a freeway run.  And, they'll all have the same deposit patterns.

If you have the option, avoid gas that has ethanol added to it.  Ethanol also makes existing fuel mixtures leaner.

Cheers,