Lean or Rich condition?

[sea157]

Can a lean and rich condition act about the same way?
Background:
Carburetor
Pilot 42.5
Main 145
Needle clip 3rd notch from top or middle notch
Low speed needle 2 turns out

Air filter: K&N

Exhaust: FMF Powercore IV
Header: Stock

Problem:
At around 1/8th to 1/4th throttle position it will start to (as I call it) tractor (sound like a tractor, Put, Put, Put, Put).
Great idle, great anywhere beyond 1/8th to 1/4th throttle.
What I am wondering is this a lean or rich condition?

Just for your information if I take the K&N filter off and replace it with a Uni filter it get worse.

Sounds like a rich condition but with the carburetor settings I have and a K&N filter and FMF exhaust I find it hard to believe it is running rich.

Any thoughts appreciated.

 

[nukacola]

You gotta check your spark plug. Use a clean one or sand it up good and drive wide open for a while then check color.

 

[alex456123]

It's lean. Up the main to either a 147.5 or a 150.

 

[sea157]

It's lean. Up the main to either a 147.5 or a 150.

Would the main have anything to do with it at that throttle position (1/8 to 1/4 position)?
I thought the main comes into play above 1/4 throttle position.

 

[YAMAHAULER]

could also be the 2 safety switches 1 on the clutch perch and the other on the front brake master but it should most definitely be running lean with stock jetting and the mods you say it has

the main jet controls 3/4-full throttle
pilot controls idle to 1/8 throttle
needle controls inbetween the 2

you can try moving the needle clip down a notch to raise the needle therefor richening it
but if that don't help and you rule out the safety switches malfuctioning
you may have to up the main to a 147.5-150
and possibly up the pilot to a 45

 

[YAMAHAULER]

Would the main have anything to do with it at that throttle position (1/8 to 1/4 position)?
I thought the main comes into play above 1/4 throttle position.

does it rev beyond that with no issues?
if so it's not the safety switches
start by dropping the needle clip 1 notch at a time and if that don't help up the pilot to a 45 and up the main to 147.5 or 150 just remember to put the needle clip back at stock position

 

[sea157]

does it rev beyond that with no issues?
if so it's not the safety switches
start by dropping the needle clip 1 notch at a time and if that don't help up the pilot to a 45 and up the main to 147.5 or 150 just remember to put the needle clip back at stock position

Yes below or above the 1/8 to 1/4 throttle position it runs GREAT.

The safety switch on the clutch perch has long been gone, I don’t think there is a safety switch on the front master (it is a 1991 model)

If I drop the needle clip or change the main to 147.5 or 150 that will be making it richer won't it?

It just seems to me it is rich for some reason in the 1/8 to 1/4 throttle position.

Remember when I switched from the K&N filter to the Uni filter it got worse.
And the K&N filter should be providing more air then the Uni.
And if you need more air it seems to me I have a rich condition.
Or am I missing something or do I not understand something?

 

[YAMAHAULER]

pull the spark plug if it's black = rich
white or grey = lean
tan-dark brown = good

with stock jetting and the fmf, k&n it should be running lean
what's the altitude there?

 

[sea157]

pull the spark plug if it's black = rich
white or grey = lean
tan-dark brown = good

with stock jetting and the fmf, k&n it should be running lean
what's the altitude there?

I will check the plug.
The altitude around here is around 400 - 500 ft (York, PA 17408)

 

[sea157]

Guys could a bad CDI unit cause this?
When this happens it seems like it is only firing every other revolution.
But once you get above or below 1/8 to 1/4 throttle position it is gone.

 

[alex456123]

No. The Cdi is just a capacitor. It either works or doesn't. If you have spark it works. If you don't its dead.

 

[sea157]

No. The Cdi is just a capacitor. It either works or doesn't. If you have spark it works. If you don't its dead.

You are correct it is not the CDI unit, I swapped it out with a known good working CDI unit and it still does the same thing.

ANYONE HAVE ANY OTHER SUGESTIONS!

I am almost to the point of selling this thing.

 

[alex456123]

Check your flywheel and see if the magnets have lost their magnetism. It happens sometimes.

 

[sea157]

Check your flywheel and see if the magnets have lost their magnetism. It happens sometimes.

Would that cause it to miss that way at 1/8 to 1/4 throttle and run GREAT everywhere else?

 

[alex456123]

I don't know. Anything is possible. It the spark strong?

 

[sea157]

Yes the spark is very strong, but it seems to miss between 1/8 to 1/4 throttle.
Almost like it only sparks ever other revolution in that throttle position.

Any ideas?

 

[alex456123]

Up your main jet to a 147.5. I don't think it's getting enough fuel.

 

[sea157]

Up your main jet to a 147.5. I don't think it's getting enough fuel.

I thought the main didn't come into play until after the 1/4 throttle position.
My problem is from 1/8 to 1/4 throttle, before 1/8 and after 1/4 throttle position it runs GREAT.

Could anything electrical cause this situation?

 

[alex456123]

No.

 

[sea157]

Alex
I have a 150 main I can put in, I will give that a try and see what happens.