Topic: 1973 Honda CB500 Four with idle issues.

[kaptainkid1]

Here is the method I used to adjust the float bowl. 3-4 mm.

I think the carb body and sliders will be clean again. I'll also delete the fuel filter when I put back my carbs.

[kaptainkid1]

I'm not going to do plug chops. I don't have any spark plugs to waste and if idles rich or lean I'll have to go by feel and run the fuel mixture at 1 and +/-1/8 if need be. Main concern only is the idle after warm up at 2000-3000 rpm range and the hesitation on getting back down to 1000rpm.   

[kaptainkid1]

All Right back to the bike problem and ton's of work and rework done. Such a headache but a learning curve is so time consuming. Please lets get it right this time.

Same problem hang ups when the bike is warmed up 2000-3000 rpms. No air leak. carb cleaning fluid spray on the carb bodys and boots.

Here is the deal....
- MAC 4 - 1 Exhaust
 - Stock Airbox
 - Stock Cam
 - Stock Carbs
 - Stock Airfilter
 - Stock jets and needle new from ebay for my model.Rebuild kit. NOW put back old clean Keihin parts.
 - I'm located at sea level.

I put back the stock Keihin Jets and brass. The only brass I didn't put back because of the rubber o-ring was rotted, was Jet cap under emulsion tube and holding the tab which push against the carb bottom.


The Keihin is to the left and KL are the right. Both are #100 jets.

So I read somewhere on the forum who had the same problem and similar set with the 4-into1 mac exhaust and did the following.
Needle adjustment set 4 notch/ clip from the bottom and turn the idle screw 2 turns out.
Anyone have an opinion on this set up???
I've chemically clean the carbs, adjusted the float correctly, clean carb body, jets, needles, etc.
Anyone think I should try something else before I pull the carb off again.
 

[Deltarider]

Same problem hang ups when the bike is warmed up 2000-3000 rpms.

Are you aware this is normal for most 500/550s and that we all turn the big central idle screw to regulate the idle cold and the idle when warmed up? Every cold start I begin by turning that idle screw to give some more throttle and as soon as engine is warm and idle hangs around 3000, I turn the screw back to have around 1100 rpm.

So I read somewhere on the forum who had the same problem and similar set with the 4-into1 mac exhaust and did the following.
Needle adjustment set 4 notch/ clip from the bottom and turn the idle screw 2 turns out.

Rule of thumb is that aftermarket exhausts do not require rejetting. Standard setting in Europe for the airscrew is 1 turn out ⁺/_- ¹/₈. In US for some reason it's 2 turns (only source: an American Honda Motor booklet edited in 1977). Needle in Europe is in middle (3rd) position). In US for some reason it's 4th notch from top (same booklet), to avoid misundertanding: top not tip.

[kaptainkid1]

Same problem hang ups when the bike is warmed up 2000-3000 rpms.
Are you aware this is normal for most 500/550s and that we all turn the big central idle screw to regulate the idle cold and the idle when warmed up? Every cold start I begin by turning that idle screw to give some more throttle and as soon as engine is warm and idle hangs around 3000, I turn the screw back to have around 1100 rpm.
Yes I'm aware of adjustments on the fly. That's not the problems because once I rev hard it comes down to 1100 or just shuts off.

[Tews19]

Cal suggested a plug chop, you should do it. I don't get how people can ride these machines yet are to cheap to spend 10 bucks on a set of plugs.

[flybox1]

And plug chops?

....and a vacuum sync?

[kaptainkid1]

Yup vacuum sync.

[HondaMan]

With the 4 into one exhaust, should he get different jets?

No.

[HondaMan]

Unless I missed it above: did you pull out the emulsifier tubes and clean them, especially their tiny vent holes? I usually clean them with a piano (or guitar!) string wire, or similar. I often open them up a couple of thousandths of an inch to help balance the overly-rich 500/550 idle with the ethanol fuels we suffer these days: it helps quite a bit.

The 500/550 have a significant (bordering on serious) problem with too-soft spark advancer springs. They were soft in 1972, and after years of heat-annealing they are even softer. This lets them "hang" at half-advance if the engine even thinks about running rich at idle, when hot. The way to "live with it" is Delta's description above (set the idle hot to 1100, then keep it alive manually until warmed up) or else cut off 1/2 turn of at least one of the advancer springs and bend out the end to reinstall that spring: this will help pull it back down to idle (the CB450 twins suffer this A LOT). This works better, and lets you set cold idle to about 800-900, resulting in a recoverable idle when hot, to about 1100-1200 RPM. Doing this to BOTH springs is sometimes required. In the 500/550, this last step also improves the low-end throttle response by stopping them from spitting back up the intake tract until air inertia overcomes the resistance better.

[jonda500]

If it won't idle while cold with some choke and the idle set where it is, you still have a carb problem.
[/quote]
That is a rash statement! Unless we are talking about 77/78 550's where the choke also raises the idle a little, Delta is right about this!
With the idle speed set to 1100rpm while hot, not one of my three bikes will idle when cold with some choke. I don't mess with the idle speed screw, instead I tighten the throttle friction screw so the throttle will stay where I put it. If I crack it open just a little, I can get 1100rpm idle speed while cold - after a minute or so the revs jump up to 3000 and then I can loosen the throttle friction screw and allow the throttle to close which will see the bike only just managing to idle at around 800-900rpm like hondaman says.
John

[DH]

Are you aware this is normal for most 500/550s and that we all turn the big central idle screw to regulate the idle cold and the idle when warmed up?

I'm sorry, but please do not propagate your technique as normal. A properly setup carb does NOT need manual idle adjustment after starting.

If your bike is experiencing a hanging idle, then you need to verify your ignition, and if ultimately, after a vacuum synch, your bike wants to idle at 2K or above when warm, then you have your idle set too high. If it won't idle while cold with some choke and the idle set where it is, you still have a carb problem.

X2........Gotta agree with cal's post .I learned this recently on my own 550. Everythings gotta be checked, step by step IN PROPER ORDER, and VERIFIED CORRECT.
before proceeding. If it's right, you won't have to use band aids like the throttle friction screw (I know I'm gonna get some heat for that remark) ....just my own experience..no offense intended folks.

[Tews19]

Cal is right as  is DH. If you have to play with the idle screw to begin with, we'll I don't wont reiterate what has been mentioned. I've posted a video of one of my 550s and I never had to play with the idle screw to warm it up. Matter of fact once the bike or any 550 is properly tuned one will never have to touch the idle screw again.

[Deltarider]

Cal is right as  is DH. If you have to play with the idle screw to begin with, we'll I don't wont reiterate what has been mentioned. I've posted a video of one of my 550s and I never had to play with the idle screw to warm it up. Matter of fact once the bike or any 550 is properly tuned one will never have to touch the idle screw again.

It ain't no big thing. Just read the Owner's Manual about starting. In stead of giving it a little throttle (as described) you may twist the Idle set Screw. Why? Well, you'll have one hand free for convenience. The only times I never had to adjust the idle was mid 70s, but that was a different gas, my friends.

[Scott S]

 I've only had one or two 550's that would idle on their own when cold. I just set the idle when the engine is fully warmed up and use the "manual choke", aka, your right hand, to help it out until it's warmed up. Usually, that's only a couple of minutes and a mile or two down the road.

[DH]

Cal is right as  is DH. If you have to play with the idle screw to begin with, we'll I don't wont reiterate what has been mentioned. I've posted a video of one of my 550s and I never had to play with the idle screw to warm it up. Matter of fact once the bike or any 550 is properly tuned one will never have to touch the idle screw again.

It ain't no big thing. Just read the Owner's Manual about starting. In stead of giving it a little throttle (as described) you may twist the Idle set Screw. Why? Well, you'll have one hand free for convenience. The only times I never had to adjust the idle was mid 70s, but that was a different gas, my friends.

The gas could very well have an effect, and could make a difference. It's certainly different now than back in the day, and different from one geographical area to the next. Valid point.
I warm my bike and wake it up with throttle for about 30 seconds while progressively opening the choke. It usually is drivable
then to an acceptable degree, not perfect, but it'll idle. My bike doesn't have a friction screw, but I don't have to change base idle. Maybe I'm confusing things, as the friction screw is more of a throttle holder, and not used to set base idle. Appologies for the misinformation. I will acknowledge that different machines act differently. guess my point is that when all is adjusted correctly, cold starting should
not be a big deal. If it is, chances are something else is going on as well, especially if things get weird as/after it gets warmed up.

[jonda500]

Cal is right as  is DH. If you have to play with the idle screw to begin with, we'll I don't wont reiterate what has been mentioned. I've posted a video of one of my 550s and I never had to play with the idle screw to warm it up. Matter of fact once the bike or any 550 is properly tuned one will never have to touch the idle screw again.

Can you post a link to that video - now that these are over 40 years old, I find it hard to believe if set to 1100rpm hot any of these bikes (pre 77 models) will happily idle in the first 30 seconds of the first time started that day on a cold morning with absolutely NO throttle used!! None of mine will even come close in cold weather.
John
ps If my bikes have already been ridden earlier the same day, then yes they will immediately after starting idle at around 900rpm with no throttle needed to keep them from stalling.

[Deltarider]

If my bikes have already been ridden earlier the same day, then yes they will immediately after starting idle at around 900rpm with no throttle needed to keep them from stalling.

Same here.

My bike doesn't have a friction screw, but I don't have to change base idle. Maybe I'm confusing things, as the friction screw is more of a throttle holder, and not used to set base idle.

It's not about that friction screw, but about the Idle Set Screw, located under the tank, right hand side.

[flybox1]

Same problem hang ups when the bike is warmed up 2000-3000 rpms.
Are you aware this is normal for most 500/550s and that we all turn the big central idle screw to regulate the idle cold and the idle when warmed up? Every cold start I begin by turning that idle screw to give some more throttle and as soon as engine is warm and idle hangs around 3000, I turn the screw back to have around 1100 rpm.
Yes I'm aware of adjustments on the fly. That's not the problems because once I rev hard it comes down to 1100 or just shuts off.

Do all your Keihin Main jets have good o-rings on them?
(These are the ones held in place by the leafspring.  Your post above was unclear if when you swapped inthe old jets, if you had new orings on them, or any orings at all....)

[kaptainkid1]

All orings  and jets new, or I was able to clean the orig. Keilin needles and emulsion tube cleaned and chemical dip. The whole carb  body were dipped too.

[kaptainkid1]

Finally after going to 4 honda CB shops and mechanics I was able to figure out the problem.

Honestly stupid mistake all ways happens to new backyard shade tree hobbyist.

So I went to Lucky Wheel Downtown Los Angeles everybody was working honda and everything was so cool there.

I was told again and again sounds like an airleak from the carb to heads. I said my rubber manifold tubes were good and I sprayed carb clean to check for leaks.

So he mentioned after the bike heats up 1/2 hour later the rubber becomes more flexible and still can leak air.

So I went home and tighten the clamps until the screw didn't move anymore. My opinion I thought they were tight enough...because I didn't want to strip the nuts...

Apprently, you need to tighten and check the rubber manifolds. Mine got air leaks when the bike get hot.... Lesson Lean!!!

" Tighten screw camps until no more movement" I hope this helps other CB riders....