Topic: Decent explanation of lean vs rich symptoms?

[Pielz]

This has always been confusing for me and I'm sure I'm not the only one. Does anyone have an easy way to know which is which? Something that can work as an easy reference for someone who's not extremely experienced? Also, there are some symptoms like power loss that can be attributed to running both lean and rich as well, right?

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[minimo]

TwoTired’s post here is a good resource to start from: http://forums.sohc4.net/index.php?topic=5410.0

This chart is also good to give you an understanding of what components are related to either condition, rich/lean, and at what throttle opening:




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[grcamna2]

Do you mean what the condition of being either lean or rich mixture feels like? or the effects on the motorcycle and how to see the evidence of that ?
Pielz,The large coils you have can sometimes lean the mixture out just slightly.

[PeWe]

Difference can sometimes be difficult to feel except for black smoke (plugs) when rich, sneezing carb on low lift when lean pilot circuit.
You need to ride the bike on a specific throttle height, check sparkplug and read it.

Air screws/fuel screws affect a steady cruising up to around 100kmh (60mph).

https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs

Carbs can be jetted for perfect plug color, but might respond very bad on twisting the throttle.

Read sites where Air/Fuel ratio is described. Good cruising ratio around 14:1 while best torque around 12.5:1.

I have just finished my carbs. Needles and main jets could be 1 step too lean noticed when twisting from 100kmh (60 mph). It ran fine otherwise.

My CB750 K6 stock carbs never needed other needle jets (emulsifier tubes) with pods and  836 + cam etc. Only 1 step richer needle when not using the restrictive stock exhausts ( HM341).  [Same carbs have  today 1 step richer needles with stock engine on HM300 replica than HM341 (when sitting on my K6 when stock) on my stock K2.]
And much richer main jets. Air screws less opened as well.

I have done 3500km on my K6 this year (April-May) to verify the carbs, plugs AND the throttle response. Not stock carbs so all jets were not known and needed to be changed except for needle tapers and throttle cut outs.

If you run stock carbs, you will find a good working base setting if searching what others have done.

Main jet and needle height are dependent on how open your exhaust is. When this can breathe, pods can open it up even more. Restrictive exhaust, pods will not increase flow much more in need of more fuel.

Like open windows and doors home. 1 door open, not much more flow inside, then open a window in another room can cause a storm inside when IN and EX start to work together.

Very important start point on other carbs than stock, needle jets (emulsifier tubes), around 3-5mm throttle lift. Must be right!! Not fixed by lower the needles loosing power on higher lifts and compensate further by increasing pilot jet which give too rich idle.

I have noticed that this picture describes carb jetting very well.
 fuel.

[gtmdriver]

Both lean and rich conditions will result in a loss of power but they feel different.

Rich mixtures cause the bike to feel 'wooly' and unresponsive with black smoke whereas lean mixtures can cause backfiring in the exhaust.

The dead giveaway though is to slightly open the choke while you are riding. If the mixture is lean the symptoms will disappear with the choke open but if it's running rich the symptoms will get worse.

The pug chop is the best diagnosis tool though.

[PeWe]

Too rich will feel and sound D-D-D-D instead of rrrrrrrrrr.

Lean cause hesitations when slowly lifting throttles and misfires.

Engine must run even at idle, no stinking. If it runs too rich then verify float bowls by clear tube process. Even correct float height can overflow if stucked or leaking valve.
Next proper size of pilot jet and air/fuel screw....
See earlier posts.

You will learn by practical tests.
It will be much easier if you tell your Bike model/ year and engine configuration with exhaust and intake.
I'm sure you will get setup examples to start with.

Ignition must be OK too. I loose HT lead can give similar results as a wrong carb setup. I have wasted time on a bad new Dyna graphite HT lead with intermittent functionality issues.
Simple copper leads,  NGK 5kohm caps and stock plugs as NGK or Denso are most reliable on these sohc bikes.

[Pielz]

Thanks for the awesome responses. I was hoping to ride a little in the next few days and I was having some power loss issues last time. I think I fixed them on the carb side but when I take it out, I was wanting a better picture in my head of symptoms to look for. That way I know just where to start.
 
It's a k7 750. Everything is entirely stock except for my exhaust but according to the manufacturer its not supposed to require a re-jet.

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[grcamna2]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

[PeWe]

Air vent tubes on carbs must not be blocked all the way to inside of carbs. 2 vents.

[Pielz]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

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[Pielz]

Air vent tubes on carbs must not be blocked all the way to inside of carbs. 2 vents.

My carbs don't actually have the air vent tubes. I read somewhere that the 77/78s had carbs with and without them

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[grcamna2]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

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Do your coil wires have resistance graphite wires in them already? if so you can run D8EA plugs

[Pielz]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

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Do your coil wires have resistance graphite wires in them already? if so you can run D8EA plugs

No, i tested and there's no resistance at all in those wires. I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better!
 
Floats are sticking a little every time I reassemble those carbs a float or two always sticks. No amount of tapping will fix it. So I guess I'm dropping the bowls! When I turn on the petcock it just flies out of the drain tubes lol.

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[grcamna2]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

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Do your coil wires have resistance graphite wires in them already? if so you can run D8EA plugs

No, i tested and there's no resistance at all in those wires. I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better!
 
Floats are sticking a little every time I reassemble those carbs a float or two always sticks. No amount of tapping will fix it. So I guess I'm dropping the bowls! When I turn on the petcock it just flies out of the drain tubes lol.

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Your floats may have little notches worn into(where they contact the float needles) them;how old are those floats?

[Deltarider]

... I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better! ...

What about the plugcaps? Do they have resistors? I've read on two Dutch dealers sites, they have seen reliability issues with the 'R' NGK plugs. No personal experience myself, just passing it on.

[Pielz]

... I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better! ...

What about the plugcaps? Do they have resistors? I've read on two Dutch dealers sites, they have seen reliability issues with the 'R' NGK plugs. No personal experience myself, just passing it on.

It's an older Dyna III system and it has wires like you'd see on a distributor cap in a car. When I checked with my multimeter, there was no resistance between the ends.

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[Pielz]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

Sent from my LG-G710 using Tapatalk

Do your coil wires have resistance graphite wires in them already? if so you can run D8EA plugs

No, i tested and there's no resistance at all in those wires. I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better!
 
Floats are sticking a little every time I reassemble those carbs a float or two always sticks. No amount of tapping will fix it. So I guess I'm dropping the bowls! When I turn on the petcock it just flies out of the drain tubes lol.

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Your floats may have little notches worn into(where they contact the float needles) them;how old are those floats?

It's possible! The floats are older. They came with the bike when I got it but looked to be in good shape and no leaks. Crap I didn't even look at the tabs or consider that as a possibility.

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[grcamna2]

Have you installed new plugs yet ? A look at a set of fresh plugs after a short ride may give a better indication.

I was going to go grab some today actually

Sent from my LG-G710 using Tapatalk

Do your coil wires have resistance graphite wires in them already? if so you can run D8EA plugs

No, i tested and there's no resistance at all in those wires. I bought a set of 4 DR8EAs today. I'll throw them in tomorrow and take it for a ride and see if it's better!
 
Floats are sticking a little every time I reassemble those carbs a float or two always sticks. No amount of tapping will fix it. So I guess I'm dropping the bowls! When I turn on the petcock it just flies out of the drain tubes lol.

Sent from my LG-G710 using Tapatalk

Your floats may have little notches worn into(where they contact the float needles) them;how old are those floats?

It's possible! The floats are older. They came with the bike when I got it but looked to be in good shape and no leaks. Crap I didn't even look at the tabs or consider that as a possibility.

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The floats(are your floats made from hard foam or brass?)have that 'tang' that is a sliding surface for the pin of the float needle to ride along as they go up and down with the needs of filling each bowl.When they get that little dimple worn in them,they get hung-up on there and stick.
Take a hard look at each float to see if they are still useable.