Topic: Running very rich, carb idiot is stumped

[UPHOTO]

Hey guys, I'm a self proclaimed "carb idiot" so this site has helped me a lot with searching for help but I've reached my end on this one after almost a year of issues.

78 CB 750F, last year took it to a shop to get the carbs cleaned and rebuilt.  After rebuilding and cleaning he couldn't get the carbs to sync and it ran really rich.  After lot's of playing with we got it to run pretty good but it was still rich, he said the problem was that the press in secondary jet's were mangled by a previous owner and that he had to take the primary down to 100's to get it to run.

After spending some time here I found replacement secondary's and did as much research as I could on what to do and how to replace them. 

Yesterday I spent the day taking the bike apart and playing with these carbs for the first time, learned a lot.  Well I replaced the secondary and then put the main's to 120 (found conflicting info on what stock is, manual say's 105 people on here say 115?) because I am running pods.  Turned out the pilot screw 1 3/4 turns and put everything back together.

Before the bike would just start up right away, no choke unless it was really cold but now the only way to get it to run is to pull the choke out all the way and then it runs very very rich.  The moment you touch the throttle it bogs out and pops and then dies.

I'm running out of ideas here and wondering if I could get some tips?  I would greatly appreciate it.

[TwoTired]

Stock exhaust?

Stay away from that shop.  They will say anything to move money from your pocket to theirs, and they don't know crap about carbs either.

Your PD carbs have, for metering fuel:
A pilot jet, IMS screw (Idle Mixture Screw), Throttle valve (slide needle), and main jet.  In addition, your carbs have an accelerator pump that shoots raw gas into the carb bore when the throttle is applied.  The pump system has two check valves, which if not cleaned and operating correctly can add extra gas to the mix.

Your bike should run at stock settings only if your induction and exhaust are unmodified.
How do you know the bike is running rich?
Do all the head pipes reach the same temperature?

It is expected that full choke needs to be applied when the bike is cold, which you gradually and incrementally remove as the engine warms.

You should familiarize yourself with the Honda shop manual the added chapters towards the rear have information about your carbs.

Be aware that the slide needle may not be adjustable for your year/model.  This could be an issue if the exhaust is not stock, and almost certainly needed with the dreaded pods.  You may have to find needles from a 77 to gain adjustability, or have a machine shop add extra grooves to the needles you have.

Cheers,

[UPHOTO]

Thank you!  Will for sure stay away from that shop.......

Exhaust is mostly stock, has a can from johnny5 on here.  All head pipes run same temp, bike has been running rich, you can see it visually blow black smoke out when you get into the higher rpm's.  Swing arm and rear wheel get black soot all over them from it.  Still doing the same thing.

Changed out the plugs too yesterday with iridiums. 

[TwoTired]

OK.  I will say that PODs are not a specification, they are a style.
Even beer has a wide flavor range under the general definition.  Aver heard of ginger beer?
So, pods have a wide specification depending on manufacturer, day of the week made (quality control), etc.

Unless you are planning on a Dyno test to give you fuel map, you will have to judge combustion conditions with your modification by reading spark plug deposit patterns.  This will give you and idea what to look for:
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

However, you need to learn about "plug chops", and have access to a test track, as plug readings need be made with the engine under power.

"Soot out the back" is really just a gross indication and could still happen after you have the ideal mixture, as the system blows accumulated soot out the system.

Iridiums aren't going to solve any problems.  And they won't likely give any benefits, unless the spark voltage capabilty is increased, as well as the spark gap.  Besides, you will be buying a lot of plugs with which to test, in your quest to retune the carbs to your pods and exhaust.

Cheers,

[UPHOTO]

Plugs were for sure Carbon Fouled.

What concerned me was the fact that the main's had to be taken down to 100's to have the bike run okay before.  Power delivery was good and I rode the bike all last year with it that way with no issues other than running rich.  It ran the same way with the air box on, or would barely run at that time because of it running so rich and than ran good after he took down the jet size, I added the pods at that time.

I don't think the secondary's were the issue because it's now running the same way it was before I took it to the shop and he played with it. 

[TwoTired]

Forget whatever the shop told you and start over learning about your carbs.

You don't have "secondary's".
At Wide Open Throttle position the main jet dominates the mixture.
At 3/4 to 1/4 throttle position, the slide needle and it's jet, at the end of the main jet holder dominates the fuel mixture.
Below 1/4 throttle position the pilot jet dominates the fuel mixture.

It could be that your slide needle jet is missing from your carbs.  This would make the carbs rich at anything above 1/8 throttle position.
It could be that the accelerator pump check valves are stuck open and allowing fuel to leak in all the time regardless of throttle twist.
The pilot jets may have been drilled out stupid large in a clumsy effort to clean them.

You are going to have to get in the carbs to check what happened to them.  And if you need to, report the findings or ask for verification from us.   Can you say you received the carbs unmolested from the factory?  Can you say they are still in that condition now?  Although we know that the carb factory specs will no longer be correct for your modifications, it should certainly be lean if the carbs were in factory condition, especially with the mods made to the bike.  You have to find out just what was changed from stock.  I've given you some clues, above.  Sorry, I haven't got a magic bullet for you.  There is not enough solid information to make a conclusion yet. 

Good luck!

[UPHOTO]

I greatly appreciate the help.

I'll check everything above but yes don't have secondary's......I replaced the press in slow jets and the main jets.  I'll check the slide needle and the accelerator pump (how do I know if it's stuck open?).

[TwoTired]

Check the slide needle jet in the carb body too.

You have to check that the two check valves in the accelerator pump only allow fuel to pass in one direction.

Cheers,

[HondaMan]

I greatly appreciate the help.

I'll check everything above but yes don't have secondary's......I replaced the press in slow jets and the main jets.  I'll check the slide needle and the accelerator pump (how do I know if it's stuck open?).

The accelerator pump, if stuck 'open', would leak fuel onto the engine from the #2 carb as soon as you opened the petcock. This is rare, though. Usually, it is stuck 'closed' (if broken or gummed up), and few folks even notice it.

If you run with that choke on, it will definitely run very rich, blow soot, and foul plugs, quick. Iridium plugs are not any sort of answer: you might wish to install D7EA plugs for now (cheaper and a little hotter) until this is sorted out.

All this said: check the carb hoses between the carbs and head. If the clamps are loose, or not in their little grooves, tihgten them. If the hoses are hard and old, at least get some 2-1/2" common hose clamps and install all 8 of them instead: this will mitigate the vacuum leaks. Contrary to popular belief, with pulse carbs (like all bikes), the vacuum leak will make the cylinder run richer, not leaner, since it will cause the carb to mix in a lower dynamic range. Lower speeds are richer in these carbs, higher speeds are leaner. If you have, for example, 2 serious vacuum leaking hoses, all 4 plugs will be dark, all the time, but the leaky ones will foul out first.

This might seem like an odd question, but...do the carbs leak gas when the petcock is on and the engine not running?

[UPHOTO]

No gas leaking at all.  I will for sure check the carb hoses, I could have screwed that up when putting it back together. 

Bought the plugs just because it was time not for to take care of any issues.

Didn't have to run with the choke on at any time but only way it will stay running right now.  Just went out to warm the bike up and see how it's behaving and it's a mess, popping and backfiring.  Got it warm and put in the choke and it garbles and struggles to run and then you touch the throttle and it just dies.  Tried playing with the idle screw and that didn't help.

I'm going to take them apart again and see if I can figure it out.

[UPHOTO]

I really need some help.....

I've been having so many issues with this bike and can't figure it out.  I've taken the carbs off sooooooo many times, gone from issues with vacuum leaks and wrong jets and now to this.

I'm now at new press in jet's, new accelerator pump, and now 120 jets (exhaust has simple can at tip no muffler and pods). 

I'm getting a POP from the #4 carb/pod, you can see the pod kind of move or expand as it pops, you can hear it in the video.

IMG_1433.MOV

You can hear the pop and how horrible it's running.  See the #4 carb reading?  I cannot get it anywhere NEAR the other readings no matter how much I adjust the screw.

Here is a video of getting the other carbs closer together and you can now hear it starving for air at initial throttle

IMG_1434.MOV

I would greatly appreciate as much feedback as I can get, I've got a ride to go on for my bachelor party at the end of the month.

I also sprayed carb cleaner at all the intake boots to see if there were any leaks and nothing.

[TwoTired]

Have you checked the gauge calibration by feeding them all from a single vacuum source?  Just need a small log manifold for that.

[UPHOTO]

I haven't and that's a good point.

Long way of doing that would also be to just run each gauge off of a single carb to see if the gauges read the same.

Could be it but you can tell that #4 is running weird.

[UPHOTO]

No that's not it, swapped the probes to different cylinders and same reading for that #4 carb.

So weird.

[TwoTired]

I can' see the numbers on the dials.  Is the white section where they settle when engine off?

Why can't you adjust 4 to be the same as number 2?