Not sure if engine is running lean or rich

[AAchops]

I recently tuned my carbs and it was kind of a pain in the ass...however...now I have the bike idling really well just under 1k.

However, when the bike is cold and I shift in first and start riding away the engine will just stop. Seems to be an engine stall or something...after a few tries it will get going but then sometimes stall out coming out of a stop sign or so until i have ridden around the block a few times. Also, at first the bike will do weird things like lag on acceleration. What I mean by that is that I will roll the throttle and get a delayed response. I get a little bit of sputtering and then a sudden over exaggeration as if its making up for the delay.

What I am trying to figure out is am I just being bad at letting out the clutch as I accelerate and since the bike is not warmed up it reacts to that more than it would if it were warmed up? or if I need to tune the carbs different/maybe rejet.

http://forums.sohc4.net/index.php?topic=5410.0

I am using this doc. as a reference however I am having difficulties because I am having symptoms of both lean and rich mixtures as stated in that doc.

total symptoms in line with those in the list (in addition to those above):

*engine surges or "hunts" when cruising at part throttle
*Popping/ spitting through carb when throttle is opened, or popping and spitting through pipe on acceleration with a closed throttle
*Black smoke from the tail pipe (sometimes when going fast in 4th or 5th on the highway)

She definitely ran better before I tuned them, but I also had to cut my outer two pipes in half due to a new set of forward controls so I am not sure if that could have affected anything.

Tips on tuning would be greatly appreciated, I have the carb tuning kit.

[TOOLS1]

Changes in exhaust pipes usually do not require re-jetting. These bikes are extremely cold blooded, which could be a lot of your problem. However since you have had the carbs off the bike, and I get the idea that it ran good before that, I would say that you have a vacuum leak. Check the rubber boots and clamps between the carbs and head. The "surging" you describe sounds like an ignition problem. That is exactly how they run when the points are going bad. I would check these things before trying to "tune" the carbs with jetting changes.
TOOLS

[AAchops]

What process do you recommend to go about checking whats going wrong in the points? or should I just replace them?

[TOOLS1]

Do they look burnt, or pitted? How many miles are on them? If unsure, replace them. Set the gaps on the new points to 0.014, Install a Dwell meter, and start the engine. Set the meter to the 8 cyl scale, and adjust the points to 21*. Then use a timing light to set the timing. Hook the light to the No#4 plug wire, and set the No#1-4. This is the set of points on the left that are mounted to the main point plate. Then hook the light to the No#3 plug wire, and set the timing on No#2-3. This is the set of points on the right, mounted on the secondary point plate.
TOOLS

[shinyribs]

TOOLS1 wrote

Do they look burnt, or pitted? How many miles are on them? If unsure, replace them. Set the gaps on the new points to 0.014, Install a Dwell meter, and start the engine. Set the meter to the 8 cyl scale, and adjust the points to 21*. Then use a timing light to set the timing. Hook the light to the No#4 plug wire, and set the No#1-4. This is the set of points on the left that are mounted to the main point plate. Then hook the light to the No#3 plug wire, and set the timing on No#2-3. This is the set of points on the right, mounted on the secondary point plate.
TOOLS

Quoted for future reference. ( I'll explain later)

[AAchops]

I did not have the carbs off the bike but i did screw with some things that could have messed up the seal i guess. Ill make sure to check that. as for the other things...i have to pop off that cap and take a good look. Could definitely be the points if that is the case.

You think the issues getting going could be linked to that or to the vacuum leak?

[Re-run]

What year is the bike? Or what carbs do you have?
The later 77/78 carbs work a bit different.
I didn't see if you mentioned that in a previous post.

[TOOLS1]

Since you did not remove the carbs, what exactly did you do to them to tune them? How was the bike running before you did the tuning? Have you adjusted your valves? Did you do anything to the points/timing when doing this tuning?
TOOLS

[AAchops]

I got the set of vacuum gauges and adjusted the air screws accordingly in order to get the bike to idle around ~900 pretty solidly. Which worked.

The bike was running better but idling worse before hand.

I did nothing else. No valve adjustments and no adjustment to points and timing.

[TOOLS1]

You should always adjust the cam chain, valves, dwell, air/idle screws, and timing before doing a carb sync. When syncing carbs, you are not adjusting the air/idle screws, you adjust the slides to where each carb pulls the same amount of vacuum. I believe you have round top carbs, and this is done with the little screw and locking nut on top of each carb. You want them to be around 7 lbs vacuum. The air/idle screws are adjusted by turning them in/out to achieve the highest idle possible, then adjust the idle down/up with the main idle adjusting knob.
TOOLS

[AAchops]

so I should reset my air screws to 1+1/4 turn and adjust all those things huh? Is this all information I can find in my owners manual or do you have any sources you could share with me?

I am not sure what a lot of those things do but I would like to learn and get this thing running top notch :)

Would I start with the main idle adjusting knob in a specific position?

[TOOLS1]

All of this can be found in the factory service manual which is available as a free download from the manuals thread at the top of the home page. As for the main idle knob, adjust it to where the idle is around 1000-1200 RPM.
TOOLS

[AAchops]

awesome, thanks TOOLS.

[Re-run]

Also, when doing a sync, #2 is your base carb, you adjust the others to match it as close as possible.

[TOOLS1]

That's only on keyhole carbs, because No#2 in not adjustable, and is used as the base carb. Round top carbs are all adjustable, and should be adjusted to around 7 lbs vacuum.
TOOLS

[AAchops]

how does one go about adjusting exactly to 7lbs vacuum?

On Tue, Aug 18, 2015 at 2:43 PM, TOOLS1 [via Honda CB750'S] <[hidden email]> wrote:

That's only on keyhole carbs, because No#2 in not adjustable, and is used as the base carb. Round top carbs are all adjustable, and should be adjusted to around 7 lbs vacuum.

TOOLS

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[TOOLS1]

I said "around" you will never get "exactly." The main thing is to have them as close to each other as you can. You attach the gauges to the carbs, and loosen the locking nut on the top, then adjust the screw to set the slide with the gauge. Be sure to blip the throttle after each adjustment, and then tighten the locking nuts. After that, you can set the idle with the main idle knob.
TOOLS

[Re-run]

So, he is positive they are the round tops? I don't see where he said for absolutely sure. Maybe I missed it. I never go the reference to air screws as I have seen people call the fuel screw, air screws.

[AAchops]

ok.

Re-run: pretty sure they are round tops but here is  a picture.



I want them to be at that vacuum pressure during idle or when I open the throttle?

When I rebuilt my carbs I set them all to shop owner manual standard setting.

Will not having dust caps on those effect performance at all?

[Re-run]

OK, yes those are round top. Sorry, just seen many people call things by the wrong name and then get the wrong info.

Now, what do you mean by dust caps? You mean the ports used for the vacuum lines? Yes, you want the screws in.

I see you have pods though, what size of jets do you have? With pods, your settings will not be the same as those in the manual.