Rough 1/8 throttle

[Joe Sull]

I drove my bike today. Runs rough 1/8 throttle. Right now, I have a .19mm (.020") washer under the clip on needles. Float level is 21.8mm (.86").

Starts and comes off the choke good.
Cold -runs good off choke
warm-Runs rough 1/8 throttle but crank a little more and it comes out of it.
Idles ok- light blip drops below 1000 and then rises back up.
I still got the 37.5 fuel jet
I adjusted the mixture screws from 3 to 3 1/2 turns with no change

I have uni-pod and the F1 cans 

I guess whats confusing me is the "CV carb jetting.pdf 4d" states that this is a rich condition. "light blip drops below 1000 and then rises back up".
I had the mixture screws at 2 and 2 1/2 before and it was rough blipping and popping from the carbs
but I can't remember if it was before I adjusted the floats.

Should I put the 40. fuel jet? Wouldn't that would make it richer?
How can I fix this cheap as possible

[movenon]

It is my understanding that in doing the blip test if the rpm drops below 1150 (or where ever your idle is set, I would adjust to 1150) then rises it is a to lean condition.

Under the assumption that the carbs are synced good I would pull those fuel jets and fuel air screws and clean the system at a minimum.  Be careful with the fuel air screws, there is a washer and small o ring there on each screw.

I wouldn't think your needles are much of a player at 1/8 throttle. Others can chime in with more experience. As far as changing the 37.5 fuel jets, call or PM Randy and install what ever he recommends. 

George

[Joe Sull]

Thats what I was thinking, George. My setup should be in a lean state but this;

"C. If the throttle is lightly "blipped" at idle, and the rpm drops below
the set idle speed, then rises up to the set idle speed, the low speed
mixture screws are probably set too rich: try 1/2 turn in, to lean the idle
mixture."

doesn't seem logical. It should be lean with the 37.5's.

[movenon]

Might help to read this file.

http://www.fjowners.com/index.php?topic=655.0

I am not carb expert.  I just try to comprehend as much as I can.  And I attend the school hard knocks and "aw shit" (I have a masters in that) .. But it is my understanding that if you do the blip test and the RPM returns rapidly and go's below the set idle rpm then returns to the set level you are to lean.

If the rpm returns slowly and settles at the set rpm level then it is to rich.

You should be able to induce both problems via the fuel air screws so you know what you are looking at. If you can't then something is plugged or out of adjustment.

If the fuel air screw is turned in on an FJ then you should be leaning the idle. Turning the screw out should be enriching the idle.

George

[FJmonkey]

doesn't seem logical. It should be lean with the 37.5's.

The 37.5 jets are just for idle, once you get on the throttle you are off the idle jets. So switching to #40 should not have any real effect on your 1/8 throttle position. And I found #40 to be a smoother less finicky idle on my FJ.

[Pat Conlon]

....and #40's are easier to keep clean. It seems that the pilots are first to plug up with our crap E10 gas here in Kalif...

To answer Joe's question, I would also check the needle jets (aka emulsion tubes) to make sure all the little holes are open. Especially the bottom holes (closest to the main jets) 

[simi_ed]

I disagree with Mark.  When I installed the #40 pilots, I noticed immediate improvement from idle to approx 1/2 to 2/3 throttle.  Better response, smoother operation and no real mileage penalty to boot.  It ran soooo much better I would have given up 5 mpg and still been happy.

[Pat Conlon]

Yes Ed, you are correct. I think Mark got confused with the air idle circuit.
The pilot jets do effect the low speed characteristics.

[Joe Sull]

Ok, I'll pull out the emulsion tubes and check them and I'll replace the pilot jets with #40's. Thanks for the replies and the advise.

I still don't understand why the blip test implies a rich idle state.

[movenon]

As you state it your blip test indicates to me you are lean.  "Idles ok- light blip drops below 1000 and then rises back up." ?

Here is another link to read.
http://www.fj1200.info/mixture_screws.htm

George

[andyb]

Pilot jets alter the same region that the mix screws tend to, it's noticable at steady-state cruise, low speeds, long gears (4th at 35mph say).

Start with fresh gas, and possibly check the synch, if it's a recent problem.  If it's always been this way, do those and then look at the brass.

[Joe Sull]

As you state it your blip test indicates to me you are lean.  "Idles ok- light blip drops below 1000 and then rises back up." ?

Here is another link to read.
http://www.fj1200.info/mixture_screws.htm

George

Which makes more sense.

That opposite what these two doc. are saying,

http://www.fjowners.com/index.php?action=dlattach;topic=580.0;attach=255
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

[markmartin]

If I recall correctly, the manual lists #40 jets in Europe and #37.5 jets in the US.   I assuming for the 37.5's were put in to meet emission standards in the US.  I interpret that to say that Yamaha preferred the bike to run on #40's, and stuck 37.5's in to pass US standards.  I put the 40's in mine. 

[Joe Sull]

Pilot jets alter the same region that the mix screws tend to, it's noticable at steady-state cruise, low speeds, long gears (4th at 35mph say).

Start with fresh gas, and possibly check the synch, if it's a recent problem.  If it's always been this way, do those and then look at the brass.

Andy, The carbs are cleaned and sync'd and I have fresh gas.

"it's noticable at steady-state cruise, low speeds, long gears (4th at 35mph say)."

Thats exactlly were the problem was.

[Joe Sull]

Ok, I took the carbs apart and checked how clean the jets were and it's all good except for something I overlooked.



There was a tutorial Andy made that mensions these two holes up the top of the throat.
I never did clean these out. I can't find the tutorial again so how do I get them clean without rounding a corner off
or getting something stuck.