Topic: Badly Overheating '75 550 (SOLVED)

[Gavin]

Hi All

Just checking in to see if any advice/experience is forthcoming. My 550's not running for more than about an hour before overheating - causing the bike to stalling whilst idling or at very low revs.

To be honest, I wasn't surprised when it did it last summer, after an hour on the motorway at speed. However, it did it saturday night after a gentle run into London... and it was about 1 degree celcius outside.

She's completely rewired by a pro, all electrical bits replaced, re-made or refurbed. Boyer Brandson ignition, and the timing's just been set. Fresh 10w40 castrol oil, which I use in all my bikes here in the UK's mixed weather.

The engine internals are stock (as far as I know). However, it's running some pod filters and a straight through slash-cut pipe. Jets are adjusted to smooth out the effect of filters and custom exhaust. The engine's also painted with matt black hi-temp paint.

I've just ordered up a color-tune kit to see if the mixture's off, but I wondered if anyone could advise on how easily the motors overheat, or what else would be an obvious cause.

Thanks guys

P.S. Pics included to give you an idea of what's going on

[fastbroshi]

  Gotta love those stock F headers.

[Sporkfly]

How thick did you throw the paint on the jugs? Paint is an insulator and will most definitely help an air-cooled engine keep its heat in.

[scunny]

my guess would be your running lean

[MRieck]

Check for vacuum leaks around the carb boots

[tygrant]

my guess would be your running lean

My first guess to, just a guess though

[Duke McDukiedook]

my guess would be your running lean

My first guess to, just a guess though

Same here, just wanted people with a few more stars to chime in first.

[Deltarider]

If you're going to use that Colortune to set mixture and create the desired blue flame at idle, you will definitely end up running lean on acceleration. I have a Colortune and it prooved useless. For a 500 or 550 mind you. 

[Really?]

That is one flippin' nice bike!!!!!

[TwoTired]

Engines run hot when fuel mixtures are lean, the spark timing is off, or there is lack of lubrication.  Verify spark timing, then go after the mixture.

You should know what carb settings you have currently (Main Jet number, throttle valve needle clip setting, idle screw setting, and idle jet number).  Then look at the spark plug deposits and report back findings.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Knowing the carbs are clean throughout is also standard trouble shoot procedure.

Also, as mentioned, carb coupler air leaks can also cause lean conditions.

You could also check that each head pipe is about the same temp as others.

If you can't verify that you have a lean mixture, you might investigate your oil pressure.  Is the idiot light working and going out after starting?
Has the oil pump been altered or tampered with since Honda put it there?


And now for the controversy...
Synthetic oils often lube better at high temps and aren't damaged as rapidly as "ordinary" oils.   If you can't solve the high temp issue by other means, consider an oil type change.  I use a semi-synthetic just as an insurance measure.

Cheers,

[Gavin]

Cheers for the replies guys.

I know the carbs are clean & the system's leak free as I've rebuilt them recently. Not toyed with the mix though as it all went back together as is... so I've maintained the original problem! 

Jet & clip details aren't written down, if I don't fix it with a mixture tweak i'll pull the carbs and see what they were set at.

My thoughts were mixture too, hence buying a colortune - which someone is now saying is useless? At least I can assess whether things are lean at idle, or perhaps enrichen a touch and then see how she runs.

Idiot light? That'll be attached to the clocks..... wherever they went. No lights, no clocks, no nothing. Just a Kickstart, lights, throttle and a brake.

I'll have a tinker and come back with the findings   

[Deltarider]

hence buying a colortune - which someone is now saying is useless?

Well, I have said it before, but here it is again.
Decades ago I bought myself a Colortune. The idea of adjusting carburettors by looking at the flame in the combustionchamber appealed to me. Results were dissapointing however. To get that desired 'bunsen' blue color at idle, I had to turn the airscrew I don't know how many turns out. As a result my 500F would not accelerate anymore. To be able to use the Colortune I needed an extra adaptor (they made you pay extra for). But there is more. When you look at the pic of my colortune, you will notice that the electrode is way too high up. On later models Colortune changed that (!) Mounted on the extra (necessary) adaptor, the electrode, that was already too high up, ended up even higher, adding considerable cc's to the combustionchamber. So the spark will be arcing in the wrong place (way too high up). Nice device to tune your lawnmower maybe. Not for 500's and 550's as these models need a rich idle to compensate the absence of acceleration jets.
BTW, I doubt Colortune can stand the high temperature of an aircooled engine when revved.
As said, later I discovered they had improved the design, but why should I reward a company that could'nt do it the first time right? I mean, a device that simple...
Personally what I would like to have is a simple CO-tester, that, with my original 4 exhausts will allow me to equalize CO on all four. There was one on the market. But in a test carried out by the ANWB (the Dutch AA) it prooved very bad. Name of the brand? Gunson, the same drunk idiot that made my Colortune.

[TwoTired]

Jet & clip details aren't written down, if I don't fix it with a mixture tweak i'll pull the carbs and see what they were set at.

The mixture adjust mechanism is different, depending on the throttle position.

My thoughts were mixture too, hence buying a colortune - which someone is now saying is useless? At least I can assess whether things are lean at idle, or perhaps enrichen a touch and then see how she runs.

I once put and exhaust gas analyzer on my 550 exhaust (4 into 4) and adjusted each idle screw for minimum hydrocarbons.  Idled beautifully, couldn't wait to see the improvement out on the road.
It sucked.  Couldn't accelerate.  Any time you opened the throttle more than a 1/16th, the engine simply wheezed and threatened to die out entirely.
As Deltarider stated, there is no accelerator pump for the 550 carbs.  When the throttle is opened, the vacuum is mostly lost in the carb throats.  This vacuum is the mechanism that pulls fuel through the jets into the carb throat.  No vacuum, no fuel, no acceleration.  The best exhaust reading was with the idle s screws turned out 5 or 6 turns from seated.  But, since that was unridable, I turned them in about a half turn and drove for effect.  Each adjust cycle improved the drivability, until finally it behaved well with a full half travel of the twist grip and good acceleration.  I checked the idle screw setting and it was right at book value for a stock bike.  Lo and behold, the bike IS stock.  Go figure.
The 550s idle rich so they can accelerate when the mechanical slides are opened.  It is not hard to believe that a colortune won't help adjusting a 550s idle setting.  The idle setting of a modified bike is set by how it responds to idle.  However, the correct procedure is to set the main jet for WOT conditions (under load), adjust the slide needles for midrange (under load), and then adjust the idle screws for proper throttle response off idle (under load).
BTW, the idle screws don't have much, if any, effect on mixture changes above 1/8 to 1/4 throttle.

Idiot light? That'll be attached to the clocks..... wherever they went. No lights, no clocks, no nothing. Just a Kickstart, lights, throttle and a brake.

I prefer an oil pressure gauge, but accept an oil light indication for minimum pressure. The stock one comes on if the pressure dips below 5-7 PSI.  Without knowing your oil is circulating, how can you expect the engine to have any life at all?
Are you getting oil at the valve adjustment inspection caps?

Cheers,

[Deltarider]

I would like to experiment with a COtester nonetheless. My bike has the four genuine exhausts and the least I could do is equalise CO of the four by simply bringing the probe from one to the other. I seem to be the only one in this forum that finds reading sparkplugnoses nowadays difficult.

BTW, the idle screws don't have much, if any, effect on mixture changes above 1/8 to 1/4 throttle.

It does if yours is a 500Four. The book says 1⁺/_-¹/₈turn out. By varying the setting between ⁷/₈ and 1³/₈ I've always noticed an increase resp. decrease in fuel consumption while riding was mostly on the highway. But maybe these models (for Europe) with 649A carbs are an exception.

[Gavin]

Cheers for the further info guys.

I'll make use of the colour tune, simply to test that the mix is rich at Idle. My thinking is that it's set spot on or lean at idle. As she heats so quickly, and wants almost no choke to start, even when very cold. Too much air going in because of the pods and the mixture I guess.

I know the oil's circulating as it's reaching the valve covers and other parts - it also helped me find all the leaky gaskets that needed replacing!  . Intention is to fit a nice oil pressure gauge down on the engine at some point.

Just bought an infra-red thermometer too, so I can get some temp readings off the engine and the individual headers too. That should help spot if the cylinders are individually running noticably different temps.

If I can narrow it down, I might then run it over to a local dyno centre and ask them to do some exhaust gas readings under load to help perfect things.

The joys of modification.

[Duke McDukiedook]

Yep, dyno is the most accurate way to dial in your carb settings.
Also pretty $$$ 

[buffalogt750]

These old bikes are not that complicated. Colortune? CO tester? You're not working on the space shuttle. Don't waste your money. If your bike wants no choke when cold starting, that indicates a rich mixture, not lean. With pods and open header, you should have 115 mains, needle in stock, or at the most, one groove richer than stock position, stock pilot jet, idle mixture screws out about 1.5 turns. There are many things to check. Oil pressure first. Put a light or a gauge so you'll know for sure. Crankcase breather not clogged (if it is clogged, bike will run until pressure builds up enough to kill the engine). Point setting (you don't have points, but lots of others do) and ignition timing, valve adjustment, cam chain tension, carbs must be clean (ALL fuel and air passages) Float level must be correct. No air leaks at carb boots and manifolds. Carbs must be synchronized (last step in a good tuneup) If you don't have gauges you can bench synch carefully and get good results. Check all these. Make sure all your settings are accurate. These are simple bikes. No magic required. Very cool and original bike by the way.

[coyotecowboy]

I was just gettin ready to say the same thing.  No choke at start means it's rich, like slobbering hog fat eye watering rich.  What do your plugs look like? 

[Deltarider]

These old bikes are not that complicated.

Agreed.

Colortune? CO tester?

Colortune? No
CO tester? Why not? How do you think mixture was set in those days at the dealer before delivery?
I find all maintenance easy to do, very easy... setting the mixture excluded. Come on, on a Four? But I like to learn.

[buffalogt750]

If you're talking about idle mixture being difficult to set,  it's simply a matter of turning each idle mixture screw in until idle drops and then back it out until you get the highest idle. If all else is adjusted properly, these engines respond well to idle mixture adjustments. 1.5 turns is a good starting point. Fine tune from there. Obtaining the highest idle from the idle mixture screws won't necessarily give you  optimum CO output, but your bike will run best.  These bikes must be fully warmed up (not just idling, take it for a good ride) before they will idle at all and before any carb adjustments can be made. As you turn each idle mixture screw, you also have to wait for the engine to respond to the change in mixture.  It may take 5-10 seconds for engine to respond. Also pods and exhaust mods do not make a big difference in idle mixture setting.

[Deltarider]

I'm afraid it's not that simple. BTW, have you read the previous posts? Once again, standard 500/550s need a rich idle to compensate the absence of acceleration jets. I can turn the screws out many turns, creating the highest idle with a beautiful blue flame no problem. Engine will purr like a kitten, but... acceleration will be terrible. Idle on these models has to be set rich to overcome running lean under acceleration. Downside is that at idle sparkplugs on 500/550s foul easily. I suppose that's why they are the only Fours that have grade 7 sparkplugs. If you ride like I do, the NGK D8ES-L or ND X24 ES-U is better however. Alas... at low RPM these plugs will foul even more.
Looking for a highest idle unfortunately can't be your guidance. And so, if a changing RPM can't guide you, setting the mixturescrews becomes difficult. That's why I would like to use a simple  CO-tester (oldfashioned dialtype by all means!!!). With 4 exhausts I could equalise them all at say 4% CO. O, yes, these bikes stink a lot.

[HondaMan]

Don't overlook the Boyer ignition. They were known (in the last century  )  to overheat and quit running on track bikes that I helped tune in the old days... They would stop sparking, then after 15 minutes of cooldown, would fire right back up for another 15 minutes. Replacing the units would solve the problem, and many of those guys ended up with Dyna instead.

[buffalogt750]

Deltarider, if your idle keeps getting higher as you turn the idle mixture screws out then some thing may be wrong with your carbs like maybe high float level, leaky float valves, floats that have gone bad and started absorbing gas making them heavier, too large pilot jets (if the number is correct maybe someone inadvertantly made them larger during cleaning) If you're fouling plugs at any time, that indicates a problem. My 1976 CB550 has pod filters, stock 4 into 4 exhaust, 115 mains and all other carb settings stock. When I adjust the idle mixture screws, turning them in too far will decrease the idle and going out too far will also decrease the idle. The highest idle is at 1.5 to 2 turns out. My bike does not foul plugs ever. I use the standard D7EA plug. The plugs always have a normal greyish tan color. ANY bike without an accelerator pump will hesitate somewhat if you whack the throttle wide open from idle. You can't compensate enough for this by making the idle richer.

[goon 1492]

Ok I just said it in another thread, man I love your bike. We need more pics and some wisdom of what that monster consists of. Oh I need a cigarette after looking at it  ....And I quit smoking almost a year ago.......

[TwoTired]

I agree with deltarider that you cannot/shouldn't maximize engine rpm with the idle screws and expect decent throttle response.  See my earlier post in this thread.  As I was adjusting the idle screws outwards for minimum hydrocarbons out the exhaust, the idle speed increased.  I had to compensate for this increase by making Idle Knob adjustments.  The process was iterative, until I got no lower readings on the hydrocarbon scale.  Great for emissions, disaster for driveability.

You can snap the throttle to 1/2 of total travel, in any gear, from idle, and get smooth predictable engine acceleration (if you don't turn the air screws out too far).  All my 550s behave this way, and are stock with the exception of the air filter element, which is a Uni NU-4055 foam type instead of the stock paper type.
While I have had a couple of plugs foul in the years that I've owned them, that was when I used choke for too long a duration (forgot to flip it off while driving) and this was in the winter when the engine couldn't really reach normal operating temp, and they were high mileage plugs, too, having been reconditioned 3 or 4 times.

F carb models (069A) differ in the idle screw design from the K models.  The F carb idle screws are solid tipped, where you can completely shut off the air bleed.  The K model (022A, 087a) idle screw tips are hollow and cross drilled.  This makes it impossible to shut off the air bleed for the idle circuit and limits the adjustment range of the.  I don't know what design deltarider's 649 carbs used for idle air bleed screws.  And, at the risk of raising his ire, I suspect his fouling issues are related to the snorkle restrictor employed on his particular model bike.  (I hope I didn't just pick a scab off an old wound     peace Delta.  That's just my 5500 mile (9000km) analysis viewpoint.)

Carb jetting can be tricky, as one adjustment range can effect another.   Pod filters reduce the fuel draw (from stock) through the existing jets, due to less pressure difference between carb throat and atmospheric.  This would normally mean the all fuel metering orifices in the carb would need to be enlarged, to restore proper mixture delivery.  The main jet primarily effects the 3/4 to WOT positions.  However, making it too rich also effects the midrange and idle somewhat.  If your driving style seldom uses WOT, then any deposit buildup could be burned off at leaner midrange throttle position, when combustion temps are higher, and maybe even idle.  The resultant plug color over all these conditions just might be tan or gray, yet the carbs are not really adjusted properly for all throttle positions.  This is one reason why Dyno testing includes a fuel map.

It would be interesting to know what kind of fuel mileage and developed power a 550 with 115 mains gets.  There are 750s that run with 110 or 105 mains along with a larger carb throat diameter than the 550's 22mm.  This would suggest that a 115 on a 550 is too large.  But, if you are happy with what you have, go with it!

Cheers,