Author Topic: Priority: Cold or warm idle (Read 1797 times)

Nortstudio · « **on:** March 18, 2011, 03:32:11 PM »

1976 CB550K

My bike has been running great, and starting from freezing, all winter, so what did I do? Mess with it! Ugh!!!!

After a ride the other day, parked but left it idling. Saw that it was idling at about 1500RPM. I remember reading that it should be lower, so I brought it down to about 1100. It idled while warm just fine.

Now it starts much tougher. I still only need choke for a second. But then I have to keep at the throtle to keep it running for a while.

My question: is it better to have a healthy cold idle, and let her run at 1500, or deal with the cold hassle and let her idle warm at 1100?

Thanks

Scott

TwoTired · « **Reply #1 on:** March 18, 2011, 03:46:15 PM »

There is no fast idle cam coupled to choke with this model. The rider is expected to hold the throttle open while it warms up.
I've not found this a problem, as you can ride it (gently) while it is cold, with partial choke.

Suited up and ready to ride. Approach the bike, get on, apply choke, and start the bike. Set choke to where is will take some throttle and drive off. As it warms, reach down and nudge off a little choke as you ride. Your hand is on the throttle to keep the R's up while riding. In a couple blocks under power the engine will be warm enough to take off choke. In another block or so, it is idling where it did the last time it was warm. Life is good.

Cheers,

Nortstudio · « **Reply #2 on:** March 18, 2011, 03:59:37 PM »

Sorry TwoTired, I think I didn't explain myself well.

I do exactly as you say, except I don't need to keep the choke on more than a momentat start up - or else it runs weird. So I flip the choke back down, let the hand/throttle get her warm, and in a few minutes, I'm off and rolling. As long as I wait until the tapper covers are warm, I'm good to go, right from the start.

The above describes how it worked while I had the idle screw set to idle at 1500 (aprox) when warm.

The other day I lowered the idle (while warm, after a ride) to about 1100 RPM. next time I go to start it cold, it takes a lot more throttle, for a lot longer, to get it up to a comfortable idle speed, to where I felt ready to ride.

I'm wondering if having the bike idle at 1500 while warm is ok? It seemed to allow me to start up easier, and never seemed bad at fully warm. I only messed it up because of something I'd read (don't believe everything you....)

Is this a matter of shouldn't have "fixed what wasn't broke?"

TwoTired · « **Reply #3 on:** March 18, 2011, 04:13:47 PM »

As I said, you don't have to warm the engine to drive it. There is no need for that. While driving, your hand is on the throttle holding it at fast idle or above.

If you MUST do a stationary warm up unattended, you don't have much choice other than twiddling the idle knob. Some like fondling that knob on the old girl while riding.

If you are using 10W-40 oil, then the oil pressure/oil flow at 1500 should be fine, whatever the temp.

I don't fondle the idle knob before or after starting. The idle knob is set with engine at operating temp. If I need choke and/or throttle to keep it going during a warm up cycle, I hold it where it is needed. It doesn't take but a minute or 3. And it warms up faster if the engine is doing some work, instead of just sitting there with only the friction of idle.

I think you adjusted the idle knob correctly. You just have to change your "warm up" routine to adapt to the way this bike was arranged to function.

Cheers,

TwoTired · « **Reply #4 on:** March 18, 2011, 04:17:50 PM »

In case you want to know. Cold engines don't atomize fuel very well. This is why you need to choke and hold the slides open more, to get more fuel/ air into the chambers. Computers handle this enrichment and idle speed change on modern equipment.
The computer on the SOHC4 is located several inches above the motorcycle.

Cheers,

dave500 · « **Reply #5 on:** March 18, 2011, 04:27:05 PM »

havent you got a throttle lock?the thunb wheel underneath the throttle?use that.

TwoTired · « **Reply #6 on:** March 18, 2011, 04:32:32 PM »

Quote from: dave500 on March 18, 2011, 04:27:05 PM

havent you got a throttle lock?the thunb wheel underneath the throttle?use that.

The 74 CB550 was the last year to have that.

I think too many people were using it as a cruise control. So, Honda stopped putting it on to limit liability.

I got my 74 Cb550 wrecked. Throttle return spring removed, and the fiction lock would hold the throttle in place. Guy fell asleep on a long cruise and crashed (pretty bad, too.)

Cheers,

scunny · « **Reply #7 on:** March 18, 2011, 04:35:57 PM »

"The computer on the SOHC4 is located several inches above the motorcycle"
best laugh I've had in a while, cheers TT

dave500 · « **Reply #8 on:** March 18, 2011, 04:36:14 PM »

the cruise control you have when you dont have a cruise control?

Nortstudio · « **Reply #9 on:** March 18, 2011, 04:43:10 PM »

Thanks folks. Looks like I'll keep trusting the computer and the throttle lock, located right between my ears. I was just second guessing myself. I think I had fallen into a comfortable routine, and then blew it out of the water with my inquisitive nagging.

Can you imagine where my curiosity /"can't leave well enough alonedness" would be if I actually had one of those new fangled computers on my bike???

.

Oh, the horror....

TwoTired · « **Reply #10 on:** March 18, 2011, 04:46:10 PM »

Quote from: dave500 on March 18, 2011, 04:36:14 PM

the cruise control you have when you dont have a cruise control?

I don't understand the question.

I believe one can fit a 74 right control group to the 75 and 76 K models.

Cheers,

Bankerdanny · « **Reply #11 on:** March 18, 2011, 05:15:15 PM »

I don't understand why nobody will answer your question. Warm. A high idle just generates more heat at the time when the bike has the least ability to col itself.

HondaMan · « **Reply #12 on:** March 18, 2011, 05:50:23 PM »

Quote from: Nortstudio on March 18, 2011, 03:32:11 PM

1976 CB550K

My bike has been running great, and starting from freezing, all winter, so what did I do? Mess with it! Ugh!!!!

After a ride the other day, parked but left it idling. Saw that it was idling at about 1500RPM. I remember reading that it should be lower, so I brought it down to about 1100. It idled while warm just fine.

Now it starts much tougher. I still only need choke for a second. But then I have to keep at the throtle to keep it running for a while.

My question: is it better to have a healthy cold idle, and let her run at 1500, or deal with the cold hassle and let her idle warm at 1100?

Thanks

Scott

This is usually a symptom of the ignition performance if the valves are not leaking, believe it or not...

If it has points: the tungsten on the points made since about 2001 is thinner and requires some warmup time to conduct well. The spark voltage is reduced until the contacts get warm. Another thing that causes this: old condensors. If they are old enough to become leaky, they sap away spark current and shorten the coil discharge until they, too, warm up, at which point they cause an increase in idle speed of [typically] more than 250 RPM. If the condesnors are not leaky but are old enough to have reduced capacitance, they provide a shorter spark duration until they warm up and regain some of the lost capacitance, at which point the spark gets a little longer. It is still shorter than with fresh condensors, though.

One way to cure the "cold points problem": my Ignition. (that's all I'm gonna say about that...).

If you have a Dyna S ignition: the connectors between the trigger pickups and the coils often has moisture-sensitive corrosion in them. This white, powdery stuff acts like an insulator until it either dries out or gets nice and warm (which dries it out), at which point the coil receives more discharge current from those triggers. Many here have also noted that the Dyna ignitions run differently between hot and cold, which has always been their signature performance since their inception in the 1970s.

HondaMan · « **Reply #13 on:** March 18, 2011, 05:52:07 PM »

Quote from: TwoTired on March 18, 2011, 04:17:50 PM

The computer on the SOHC4 is located several inches above the motorcycle.

TT: that's got to be the quote of the year!

BobbyR · « **Reply #14 on:** March 18, 2011, 06:00:58 PM »

I am a reformed "knob fondler" I just ride her till she warms up. The other point is the tachs probably were never very accurate and did not improve with age. You may be higher or lower than 1500. 1500 is a very commonly quoted idle speed around here for years. Above that I lose some engine braking.

Nortstudio · « **Reply #15 on:** March 18, 2011, 06:38:38 PM »

Appreciate the pros weighing in. I can't believe I got TwoTired AND HondaMan in the same thread! I must be doing something horribly wrong.

HondaMan, thanks for the heads up. I did a full tune-up before the winter (but rode all through the east coast winter, so a check might be in order). But at that time, I kept the ignition parts that came on the bike - and the way this bike had been "cared" for, it would NOT be a shock if I needed a new points/condenser setup.

TT, I too touched the "knob" when I first got the bike, but I found that comfortable zone, and finally started letting well enough alone. Then of course, today I decided well wasn't well enough, and messed it up

. I'm going to see if I can find a happy medium between my easy startup routine and the warm idle not being too high.

If 1500 is potentially incorrect, it seems it may be wise to try it a bit lower, if all runs well. As bankerdanny pointed out - probably not best to be running unnecessarily hot when the engine warms up.

Is there a consensus on an optimum setting (on my less than accurate tach)? I've read different things.....

BobbyR · « **Reply #16 on:** March 18, 2011, 07:14:09 PM »

I balance I idle vs engine braking. I use the motor a lot to slow down. With a carb synch I got it lower.

Nortstudio · « **Reply #17 on:** March 18, 2011, 07:26:41 PM »

I use engine braking a ton, which is another reason I hoped to find a happy medium between comfortable startup and warm idle.

I'll get it, eventually....

BobbyR · « **Reply #18 on:** March 18, 2011, 07:42:55 PM »

If you want to synch your carbs I have the gauges. I have to do mine again this year.

Nortstudio · « **Reply #19 on:** March 18, 2011, 07:59:48 PM »

Thanks Bobby. I got a set too - figured I'd get that out of the way because it's something I'd need again. I'll probably do a whole tune up again - despite it not being 3000 miles. The last one was my first ever, and I could use the practice

TwoTired · « **Reply #20 on:** March 18, 2011, 11:57:58 PM »

Quote from: Nortstudio on March 18, 2011, 06:38:38 PM

If 1500 is potentially incorrect, it seems it may be wise to try it a bit lower, if all runs well. As bankerdanny pointed out - probably not best to be running unnecessarily hot when the engine warms up.

If the bike has forward motion, or any breeze flowing past the fins, 1500 isn't going to overheat the engine. I don't know a valid reason to let the bike sit idling longer than a street light cycle. I suppose traffic jams can be an exception in places where lane splitting isn't allowed.

Quote from: Nortstudio on March 18, 2011, 06:38:38 PM

Is there a consensus on an optimum setting (on my less than accurate tach)? I've read different things.....

Yes, tachs CAN be inaccurate. Especially when a 750 tach has been fitted to a 550 (BTDT). I usually set my 550's at 1100 tach indication when at full operating temp. All of them. It is usually happy there unless due for a tuneup.

Cheers,

Nortstudio · « **Reply #21 on:** March 19, 2011, 05:12:14 AM »

1100 RPM it is then. I have my fair share of idling at stop lights here in NYC, so this seems to make the most sense all around.

Thanks TT

Stev-o · « **Reply #22 on:** March 19, 2011, 07:58:02 AM »

Nort - you did a full tune up last fall but didn't change the points?

Nortstudio · « **Reply #23 on:** March 19, 2011, 08:31:04 AM »

I didn't. It was all new to me, and when the ones I had worked, I just left them. Bit of a regret now, but I knew I'd be doing a whole fresh tune-up before another 3000 miles passed - just to double check my work. Figured I'd swap them out then (soon, since the weather is finally turning agreeable around here for curbside wrenching).

News:

Author Topic: Priority: Cold or warm idle (Read 1797 times)