Topic: Runaway Revs, Low mpg, air pods....connected issues?

[mrbreeze]

It's a good feeling to get things to smooth out and run right. I'm betting your 12 MPG days are over!

[evinrude7]

Alright...the bike is running like a top now. There was no major air leak or vacuum leak and there was no issue with the ignition advancer springs. The guts of the carbs were also fine. It was exactly as you folks said - starting from the very beginning and going through all items one by one. The following were found:

1. valve clearances were off
2. the air screws, at one turn out, were providing way too little air to the mixture
3. the carb synch was way off, though fixing issues 1 and 2 probably shifted the carb synch anyway

Truth be told, I did enlist the help of a local honda stalwart to help me go through this and I'm glad I did. At one point, I had to decide that I wanted to .... well .... ride my bike!

But for the interest of completing this thread, I wanted to update you all on our findings.

I still haven't filled my tank yet so I don't know how much better my fuel economy is. But once I get  a warm idle it stays right where it is.

Thanks again, everyone, for all the pointers you gave. I still need to learn this all myself if I'm to have this bike for a long time. So this has been a learning experience.

way to go.  time to enjoy the work you've done. 

[jonda500]

Altering the air screw and valve clearance settings cannot physically 'shift the carb sync'!
John

[hman0217]

It's a good feeling to get things to smooth out and run right. I'm betting your 12 MPG days are over!

Yes indeed! I actually still think I'm a little rich but, even then, far improved over 12 mpg.

On that note, I've put about 80 miles on the bike since we got it (relatively) dialed in. I know that's a few more miles than recommended for the plug chop but nonetheless ... If I pull the plugs and they're black, how incrementally should I open up the air screws further, between plug chops, in the search for that perfect mixture aka chocolate color? Quarter turn? Half turn? Full turn?

Altering the air screw and valve clearance settings cannot physically 'shift the carb sync'!

Okay. Yea I know the air screws come after syncing but I thought that valve clearance issues could play a role. I stand corrected!

[flybox1]

General riding is not a 'plug chop'
now you have plugs with deposits from many throttle positions over many miles.  This tells you nothing.
A plug chop is ONE throttle position, under load, for just enough time for deposits to form giving you a 'picture' of the air fuel mixture for that throttle position.

[hman0217]

way to go.  time to enjoy the work you've done.

Thanks. A nice long epic ride would just about balance this out!

[flybox1]

Start with an idle plug chop to ensure your  IMS (idle mixture screws) setting is correct .
ride the bike with current plugs.  get the engine hot.
park the bike and put in a set of NEW plugs, and start the bike.
Idle, under a fan, 4-5 minutes.  no blipping of the throttle.
pull the plugs and post us a picture to see.
 

[TwoTired]

Valve clearances DO effect carb sync, as it effects the way the cylinders breathe, and that effects the vacuum developed.

The air screws only adjust the pilot circuit, which determines the minimum fuel mixture needed by the engine to run.  However, if your carbs don't have an accelerator pump,  the idle mixture must be over rich to allow for engine pick up when the slides are lifted.  This action raises carb throat pressure to that nearer to outside atmospheric.  And, the magnitude of the pressure differential effects how much fuel is drawn through the metering jets. Raising the slides admits more air.  But the vacuum loss draws less fuel, resulting in engine wheeze/ no power, unless the pilot/idle mixture is set over rich.  Personally, I think idle/pilot mixture is the last part of carb adjustments after Intake and exhaust changes, due to the fact that the mains circuit leaks some even at idle throttle position.  For this reason, the main jet is optimized first with W.O.T. Plug chops.  Needle height is optimized with 1/2 throttle plug chops,  and the air bleeds are adjusted for smooth and predictable engine pick up under engine load and throttle twists of up to 1/2 remaining throttle travel.

[jonda500]

Thanks for this explanation TT, your posts are my most valuable resource in learning about my honda carbs. So I stand corrected - valve clearances CAN affect carb sync readings although the slide heights wont be altered by setting them.
I am pleased to see written what I always thought was true about jetting - which is that the main jet size DOES have an effect on the mixture at other throttle positions, even at idle.
John 

[Airborne 82nd]

The runaway revs are hard pointer to either a major vacuum leak, or an ignition advancer problem. I struggle to believe the fuel switch is causing/resolving the issue unless you've also got a wonky inline fuel filter as part of your non-stock setup?

To set your idle, warm up the bike, set the idle, then leave it be. If your bike always starts without choke, its likely you're rich on the idle circuit. If you perform an Idle Plug Chop, what do the insulators look like?

Lastly, are you sure you wish to chase down these problems as you have the airbox going back on? Any settings/tuning changes you make, may well need to be redone once the airbox is back on (except of course ignition/timing issues).

[/color]

+1 why fool with it just wait till  your new parts come in other wise you are pissing in the wind and uphill you will just be tuning  over again.

[hman0217]

Start with an idle plug chop to ensure your  IMS (idle mixture screws) setting is correct .
ride the bike with current plugs.  get the engine hot.
park the bike and put in a set of NEW plugs, and start the bike.
Idle, under a fan, 4-5 minutes.  no blipping of the throttle.
pull the plugs and post us a picture to see.

Alright well I'm already bracing myself for a shake of the head because these spark plugs don't look like anything happened to the but, as requested, here are my plug chop pictures. I still have the plugs incase you want different perspectives.

Now a little background... I rode about 6-7 city miles home before doing this, so I think the engine was sufficiently hot. A note on that ride though... When I rode into work earlier, the engine ran pretty good, though it hesitated slightly while climbing the bridge. Not he way back, however, when I started it up it was not smooth at all and was making a lot of subtle popping sounds. After warming in up for 4-5 minutes, I started on my way and when I started laying into it it lost about half it's power - a bit unnerving as I was about to pop onto a small stretch of highway and I was struggling to push 50 mph. After about 10-15 minutes, the issue subsided and I was running pretty well.

In my very limited knowledge, I thought this meant maybe the plugs were fouled and the sparks weren't happening. But when I pulled the plugs with about 120 miles on them, three were pretty neutral in color and one was white.

Anyway onto the plug chop...disclaimer is that I live on the third floor of an apartment building in the city with no garage or place to plug a fan. There was about a 5 mph breeze and it's in the high 50s outside so I hope that's not too distant from a fan blowing.

I took out the plugs within five minutes of shutting off the hot bike (burning my hands repeatedly) and put in the new plugs. I started up the bike at 10:43 and ran it until 10:48 pm, at which time I shut it off. Then I pulled out the new plugs (burning my hands a few more times) and replaced them with the original plugs.

Without further ado, here are the pictures (the number on the plug box corresponds to the cylinder):

EDIT: I do realize these pictures are rather poor but I'm dead in the water til daylight. The flash just obscures everything and it's otherwise too dark. I hope to post better ones tomorrow.

[hman0217]

and for what it's worth, here are shots of the plugs after 130 miles of riding. These don't have numbers but are posted in order  of #1 to #4. Would I be correct in concluding #3 is lean?

[Jimray23]

They are all lookin way lean

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[calj737]

You have a serious insufficient fuel issue. Simple as that.

You do not need to allow your bike to idle/warm up for 4-5 minutes. 1-2 minutes, using some choke if necessary, then off you go. These are air-cooled engines, and they need airflow over them else they overheat.

[hman0217]

You have a serious insufficient fuel issue. Simple as that.

You do not need to allow your bike to idle/warm up for 4-5 minutes. 1-2 minutes, using some choke if necessary, then off you go. These are air-cooled engines, and they need airflow over them else they overheat.

I see... How much would you recommend turning in the air screws between plug chops? These are the stock air screws. If it matters, these are #110 mains in the carbs, stock airbox and K&N air filter.

Also, am I correct to go right to the air screws? or would clogged jets be suspect and how would I even confirm that? I did burn off the fuel in the carbs before letting the bike sit for an extended period earlier this spring but I'm not sure I should just assume that it's out of the question. But I mention this because the poor running issue just kicked in again after about 120 miles of riding and I hadn't touched the air screws in the interim. Then again, would #3 even have had a chance to whiten up like that if it was ever running an optimal mixture in the first place?

[Jimray23]

If u changed to pods and didnt re-jet. You need to rejet for the pods

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[hman0217]

If u changed to pods and didnt re-jet. You need to rejet for the pods

--------------------------------------------------
Jim

Oh no, the title of this thread is now deceiving because I HAD pods on here at the beginning and I switched back to the stock airbox. With a Mac 4-into-2 and the K&N filter, I up'd the jets from a 105 to a 110.

Also, prior to working on this earlier this month, a couple of the plugs were black as night (with pods and 120 mains, which were unwisely installed by someone else), so I was actually running rich (and getting abysmal fuel economy). I didn't do anything to the carbs since we re-tuned everything earlier this month except we sync'd them and turned out the air screws (perhaps too much I'm thinking). I can't imagine that the 110s with this setup would not be insufficient flow based on what I've read:

from http://forums.sohc4.net/index.php/topic,103861.0.html

FROM; DO THE TON...

Quote
MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)



Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.

So it looks like I'm +2 for the 4-into-2 and +2 for the K&N filter and then -2 for the "subtract two sizes" at the end. 105+2+2-2= 107. Thus, if anything, it looks like I'm sending MORE fuel in than recommended, which would bias the mixture towards rich, no?

[flybox1]

MAINS?!?!?    Main jets do not supply any fuel at idle.
You gotta deal with getting the right pilot jet and IMS settings first.
 

Idle plugs should look like this if you have accellerator pump carbs....tan at the tip, white down inside


these are good if your bike does NOT have an accellerator pump

[Jimray23]

If u changed to pods and didnt re-jet. You need to rejet for the pods

--------------------------------------------------
Jim

Oh no, the title of this thread is now deceiving because I HAD pods on here at the beginning and I switched back to the stock airbox. With a Mac 4-into-2 and the K&N filter, I up'd the jets from a 105 to a 110.

Also, prior to working on this earlier this month, a couple of the plugs were black as night (with pods and 120 mains, which were unwisely installed by someone else), so I was actually running rich (and getting abysmal fuel economy). I didn't do anything to the carbs since we re-tuned everything earlier this month except we sync'd them and turned out the air screws (perhaps too much I'm thinking). I can't imagine that the 110s with this setup would not be insufficient flow based on what I've read:

from http://forums.sohc4.net/index.php/topic,103861.0.html

FROM; DO THE TON...

Quote
MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)



Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.

So it looks like I'm +2 for the 4-into-2 and +2 for the K&N filter and then -2 for the "subtract two sizes" at the end. 105+2+2-2= 107. Thus, if anything, it looks like I'm sending MORE fuel in than recommended, which would bias the mixture towards rich, no?

When it says +2 thats 2 steps. Each step is 2.5.

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[hman0217]

If u changed to pods and didnt re-jet. You need to rejet for the pods

--------------------------------------------------
Jim

Oh no, the title of this thread is now deceiving because I HAD pods on here at the beginning and I switched back to the stock airbox. With a Mac 4-into-2 and the K&N filter, I up'd the jets from a 105 to a 110.

Also, prior to working on this earlier this month, a couple of the plugs were black as night (with pods and 120 mains, which were unwisely installed by someone else), so I was actually running rich (and getting abysmal fuel economy). I didn't do anything to the carbs since we re-tuned everything earlier this month except we sync'd them and turned out the air screws (perhaps too much I'm thinking). I can't imagine that the 110s with this setup would not be insufficient flow based on what I've read:

from http://forums.sohc4.net/index.php/topic,103861.0.html

FROM; DO THE TON...

Quote
MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)



Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.

So it looks like I'm +2 for the 4-into-2 and +2 for the K&N filter and then -2 for the "subtract two sizes" at the end. 105+2+2-2= 107. Thus, if anything, it looks like I'm sending MORE fuel in than recommended, which would bias the mixture towards rich, no?

When it says +2 thats 2 steps. Each step is 2.5.

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

Oh so I'm right on the money! 2.5 * (4-2) = 5 and 105 +5 = 110.

[Jimray23]

What r ur air screws set at

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[hman0217]

What r ur air screws set at

--------------------------------------------------
Jim

Well it looks like 1, 3 and 4 are two whole turns out and #2 is about 2.5 turns out. Waaaaaaaay more than shop manual I realize. Should i back it up to 1.5 turns? or 1 turn out even?

And question: since the jet is larger, do I actually WANT more opening in the air screws? Or is that already done via the increased air flow from the filter and exhaust leaving the air screws where they should be?

[flybox1]

Fuel supplied is cumulative, so you cant settle on a main jet till you have the right pilot jet, and needle clip position.
Main jets are the LAST piece of the puzzle.

Pilot jets and IMS first, before you overheat your engine......please.

[Jimray23]

I would set the air screws to 1 turn out. Im probably wrong but I think turning the screw in gives more fuel which is what u need desperately. Do u no what size ur slow jets are and if they are stock.

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[Jimray23]

Fuel supplied is cumulative, so you cant settle on a main jet till you have the right pilot jet, and needle clip position.
Main jets are the LAST piece of the puzzle.

Pilot jets and IMS first, before you overheat your engine......please.

Main jets do supply a very minute amount of fuel at idle.

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils