Topic: How fast does a cb550K need to be going for decent air cooling?

[tkarahalios]

I have a 1975 CB550K1. I have gone through the bike carefully and done the 3000K service as well as carb syncing. The bike runs better than it ever has. It idles well at 1000rpm steady. This weekend I went for 3-4 hour ride and had no problems until the last 45 minutes of riding home in traffic. It was stop and go for a while and the bike stalled 2 or 3 times. It had not stalled all day until that point. Also at one point near the end it started to sound funny and the clutch felt a little different when engaging.

I believe I was overheating or getting very close to it. I have a temperature dipstick that was showing 110C on the oil.

Any ideas what I should do to try to minimize this being an issue in the future?
Is there a minimum speed I should move at if possible on the shoulder of the road to get airflow going?
Is there any reason to consider looking at the air/fuel mix screws (now at 1.5 turns out) to adjust for a cooler running motor?
Does the fuel octane have any influence on engine temp?
If I find an oil cooler would that be wise to add the stress on the oil pump to push through it?

Thanks for any thoughts. I plan on riding a lot this summer and hope to take any precautions I can to keep the motor cool and healthy.

[Bodi]

These are not great parade bikes. In stop and go traffic, "go" gently to make minimum heat - gunning it when there's a gap then stopping hard is really not a good idea. Air temperature and humidity have an effect, high humidity is more detrimental as humid air is less dense and doesn't cool as well; temperature differential is all that matters in thermodynamics so with the engine at 300+ the difference between ambient 70 and 90 is not a big factor - about 8%.
An idling engine should be making the least heat it ever will. Our fanless engines will overheat if idled with no wind, but it takes quite a while.
The carbs are normally tuned quite rich at idle, just shy of where the plugs would carbon up. This is to make throttle opening work smoothly - a stoichiometric idle mixture would have severe stumbling and dying on our slide carbs without accelerator pumps (only some 750s have these). A rich mixture also burns cooler.
Air cooled engines do run hot and even overheat to seizing especially at low speed if worked hard - like when climbing a long steep hill in first gear. I have experienced this.
The ring gaps in an aircooled engine are larger that for watercooled to minimize seizing at the higher temperatures possible. Air cooled engines actually cool better in really hot places because the temperature differential is so much higher... they can get well over 300 degrees while a water cooled engine radiator will pop its cap by 250. Of course car aircooled engines universally have blowers forcing air past the hot bits.
Anyway... these bikes do run different when really hot: the oil is much thinner so the clutch feels different, and the overall sound will change.
As long as the motor doesn't seize, it won't be damaged unless abused (don't run full throttle through the gears when the traffic jam suddenly opens up).
- Using synthetic oil helps, it holds viscosity better at high temperature (not trying to turn this into an oil thread, honest!!!)
- avoiding traffic jams is wise, taking to local streets (where you at least move) in order to avoid highway bottlenecks is wise.
- fuel octane makes no difference.
- incorrect carb tuning and ignition timing can make large differences in heat produced.
- oil coolers without fans will not help in traffic jams - they get cooled by airflow as well. Only useful in "hopped up" engines where heat production is greatly increased at high throttle/high rpm (and high wind, hopefully) in my opinion at least. I've only seen one bike add-on oil cooler with fans, and it looked pretty "home-made".

Stopping and taking a break while traffic is clogged is a good idea. With the road moving at walking speed, you'll only lose about 3 mles in an hour of sitting it out. That's 3 minutes at 60mph...

[Deltarider]

I believe I was overheating or getting very close to it. I have a temperature dipstick that was showing 110C on the oil.

That in itself is not alarming.

Any ideas what I should do to try to minimize this being an issue in the future?

You can reduce oil temp by letting the engine make more revolutions. Just shift down.

Is there a minimum speed I should move at if possible on the shoulder of the road to get airflow going?

There are minimum speeds that you should consider moving to a different means of transport like a moped or a pedal bike. Although the CB500/550s are thermally healthy, they were not ment for stop and go traffic like rides in town.

Is there any reason to consider looking at the air/fuel mix screws (now at 1.5 turns out) to adjust for a cooler running motor?

Yes, certainly. When I enter town again after a ride even an 1/8 of a turn can make a lot difference in engine heat.
Bodi gave good guidelines.

[ekpent]

Out of curiosity is the bike bone stock or does it have a different pipe, filters etc.. Jetting changes may help if there has been mods. Proper gas mixture is important for cooling an air cooled engine.

[cocinero196]

.....I have a temperature dipstick that was showing 110C on the oil.

Hi! May I know what brand & where you bought a temperature dipstick for your cb550k? pls send me a link to the temperature dipstick if possible
I actually started a thread re: oil temp gauge, no luck there.

[Lostboy Steve]

Changing to an expensive synthetic and zddp have helped a lot in my case. NJ gets really #$%*ty sometimes. The problem here is that its not stopped traffic, its crawling traffic. So not fast enough to cool, but not slow enough to shut the bike off and "walk" it. I was thinking about an oil cooler, but I doubt the difference it will make at a standstill  is even worth the trouble. I wish they would allow lane splitting in NJ so I could at least get a little airflow when the traffic is terrible.

[tkarahalios]

So my bike is mostly stock including the airbox and air filter. I have an aftermarket Mac 4 into 1 exhaust but was told that it is set up for stock carb settings. I believe that the carb jets are all stock. I never opened them up myself yet. I had Harrisluv go through them about a year ago and I think he reported back that everything was stock and original brass.

1) I am at 1.5 turns out on the carb air fuel mixture screws and it idles real nice and runs as good as it ever has. I was considering messing around with setting them at 1.25 turns out based on the theory that "a richer engine runs cooler". Does that make sense or should I just leave well enough alone?

2) I was under the impression that using synthetics was not a good idea for wet clutches. Without turning this into an oil thread, I guess there are synthetics that are good to use with a 1975 CB550K?

3) So is driving in a lower gear better for cooling the engine? I imagine the oil is flowing faster but the engine is also working harder than if you were coasting at the same speed but in a higher gear.


I took a picture of my oil dipstick thermometer. I bought it 2 years ago on eBay but can't seem to find them on there anymore. I recall it was made in either Taiwan or Vietnam. The brand on it is QSPS. I'm not sure of the quality but I will probably test it in boiling water to confirm it's reading this weekend.
 

[Bodi]

It's the additive package, not the base stock - synthetic vs prehistoric - that makes and oil bad for wet clutches.
You can buy bike-specific synthetic oil at bike shops (Motul, Spectro, etc) but they tend to cost a bundle. Or use synthetic diesel oil... Rotella T6 is pretty cheap at Wally World.
Amzoil has good synthetic bike oil. They also claim 100% synthetic base, most other brands' "Full Synthetic" oils are maybe 50% actual synthetic - tUSA law allows this. A European brand that says "full synthetic" is, as far as I know, actually 100% synthetic. Unless it's reblended for the USA, I dunno?
You can get ZDDP additive that improves wear resistance on our direct contact rocker cam engines. No modern car gasoline engine uses direct rocker cams, so no modern gasoline car oil will have enough zinc to avoid rocker and cam wear, avoiding some pollution or something. The diesel oil has more to avoid engine wear. Adding a bit even to diesel is a good idea.
Avoid any oil or additive with teflon or moly.
Automotive oils with current SAE ratings have friction reducing additives that are not good for wet clutches.

[Deltarider]

1) I am at 1.5 turns out on the carb air fuel mixture screws and it idles real nice and runs as good as it ever has. I was considering messing around with setting them at 1.25 turns out based on the theory that "a richer engine runs cooler". Does that make sense or should I just leave well enough alone?

As I wrote before, that can make a big difference. On mine an ¹/₈ increment and the difference is already significant. You can always try, can't you? Just remember where the airscrews were, in case you don't like the result. For your model Honda prescribes 1 ¹/₂ ⁺/_- ³/₈ anyway, so what's keepoing you? I presume your pilot jets are 100% clean and there are no airleaks.

So is driving in a lower gear better for cooling the engine? I imagine the oil is flowing faster but the engine is also working harder than if you were coasting at the same speed but in a higher gear.

No, it isn't. Again, why not try it? Works for me. Just remember that your engine will always be somewhat hotter when operated in cities with stop and go traffic. Anyway, I'd start with the adjustment of the airscrews. Even only ¹/₈ of a turn richer can do it and you'll have a better driveability on acceleration too.

[Duanob]

So my bike is mostly stock including the airbox and air filter. I have an aftermarket Mac 4 into 1 exhaust but was told that it is set up for stock carb settings. I believe that the carb jets are all stock. I never opened them up myself yet. I had Harrisluv go through them about a year ago and I think he reported back that everything was stock and original brass.

1) I am at 1.5 turns out on the carb air fuel mixture screws and it idles real nice and runs as good as it ever has. I was considering messing around with setting them at 1.25 turns out based on the theory that "a richer engine runs cooler". Does that make sense or should I just leave well enough alone?

2) I was under the impression that using synthetics was not a good idea for wet clutches. Without turning this into an oil thread, I guess there are synthetics that are good to use with a 1975 CB550K?

3) So is driving in a lower gear better for cooling the engine? I imagine the oil is flowing faster but the engine is also working harder than if you were coasting at the same speed but in a higher gear.


I took a picture of my oil dipstick thermometer. I bought it 2 years ago on eBay but can't seem to find them on there anymore. I recall it was made in either Taiwan or Vietnam. The brand on it is QSPS. I'm not sure of the quality but I will probably test it in boiling water to confirm it's reading this weekend.

there's your problem, you got a temp gauge to obsess over!  Just like my BatteryBug if it's not a perfect 14.5v charging or at least 75% capacity for starting, I worry, usually for no reason. 

[Lostboy Steve]

So my bike is mostly stock including the airbox and air filter. I have an aftermarket Mac 4 into 1 exhaust but was told that it is set up for stock carb settings. I believe that the carb jets are all stock. I never opened them up myself yet. I had Harrisluv go through them about a year ago and I think he reported back that everything was stock and original brass.

1) I am at 1.5 turns out on the carb air fuel mixture screws and it idles real nice and runs as good as it ever has. I was considering messing around with setting them at 1.25 turns out based on the theory that "a richer engine runs cooler". Does that make sense or should I just leave well enough alone?

2) I was under the impression that using synthetics was not a good idea for wet clutches. Without turning this into an oil thread, I guess there are synthetics that are good to use with a 1975 CB550K?

3) So is driving in a lower gear better for cooling the engine? I imagine the oil is flowing faster but the engine is also working harder than if you were coasting at the same speed but in a higher gear.


I took a picture of my oil dipstick thermometer. I bought it 2 years ago on eBay but can't seem to find them on there anymore. I recall it was made in either Taiwan or Vietnam. The brand on it is QSPS. I'm not sure of the quality but I will probably test it in boiling water to confirm it's reading this weekend.

there's your problem, you got a temp gauge to obsess over!  Just like my BatteryBug if it's not a perfect 14.5v charging or at least 75% capacity for starting, I worry, usually for no reason. 

Aint that the truth.

[cocinero196]

I took a picture of my oil dipstick thermometer. I bought it 2 years ago on eBay but can't seem to find them on there anymore. I recall it was made in either Taiwan or Vietnam. The brand on it is QSPS. I'm not sure of the quality but I will probably test it in boiling water to confirm it's reading this weekend.

Thanks! No luck yet w/ the cb550 oil temp gauge dipstick