idle mixture problem / colortune issue ? / Going insane ?

[TDodge7]

color tuned and synced again , this time I took all the screws to lightly seated , and all cylinders reacted the same (which is good to know since I thought I might have opened carb 4's hole up some getting the broken tip out way back when )
on the colortune there was nothing at lightly seated

1/2 turn out gave a dim blue light with some white sparkles every once in a while

1 turn out gave me bunson blue

1 1/2 turns out gave me a somewhat greenish orangish bluish color

2 turns out gave me a yellowish orange color

2 1/2 gave me yellow

I went ahead and left them all at 2 turns out . Since I have that range of adjustment I'm thinking the pilot's are correct . The bike seems to ride well in the low rpm's now , tho the idle is a bit lopey (which I'm willing to deal with ) . I'm going to run it for a little bit and see how it does , it's going to rain the next 2 days so we'll see it it magically changes mixture again . She sure rides nice though .

[DGXSER]

On Thunderstruck, A PO had drilled the exhaust with 1/4" holes around the baffle plates to open it up just a bit. No matter how I tuned or twisted any screw on that bike, it always idled just a little lopey here and there, and it always popped on heavy decel, like engine braking or such.

But the plugs were always a nice color and there are more than a couple on here that I say would vouch that she ran like a scalded dog. No lean or rich issues. Sometimes, close enough is close enough.

[TDodge7]

Ehhhh , well I guess I'm kind of starting over again , as now that I've actually been taking the xs out on the highway I see that my original top end rich problem is still alive and well . In the neighborhood I only have small spots where I can go wide open and it's always done it well , but now out on the street/highway I have enough time to stay wide open for it to load up and brick wall at 6.5k ish . I went and ordered a set of 132.5 mains to replace the 135's in it now , they should hopefully be here by the time the rain ends next week . Mid range seems to always be fine , and I think I have a handle on the idle situation (though that may change as the new mains go in , we'll see) . Other than that she rides pretty well . In case anyone is hopping into this thread without reading it my current specs are

1980 xs1100sg
79 carbs
135 mains (stock 137.5)
42.5 pilots (these are stock)
middle position on needle (stock position)
float height 27.5mm (down from stock 25.5)
1 7/8 turns out on mixture screws across the board ( they all adjust the same)
k&n filter
Kerker 4 into 1
drilled air box bottom


bike needs choke to start unless warm , idle is very very low until it warms up . Once warmed up it exhibits rich symptoms up top (sounds like it's gargling at around 6.5k , and has a slight flat spot between 2500-3000rpm but only on slight throttle , a healthy turn on the throttle and it goes right through it . Sometimes at idle if you crack the throttle open wider than just a blip it takes it a while to settle back to idle , but it does this even when it's set way rich , it could just be that they're cv carbs and it takes a second to settle , I'm more used to non cv carbs where the throttle slide goes where you tell it to go when you tell it to .

[TDodge7]

I take back the choke needed to start part , I usually keep it inside where the a/c is so when I pull it out it needs choke . It's been sitting outside in the sun since yesterday so I was able to just start it with partial throttle , hold it there for a while and let it sit there idling on it's own ....good thing ? maybe , we'll see . My jets are shipped so I can only play the waiting game now .

[dbeardslee]

Just a note on the jet sizes. When I first got Betsy she'd foul plugs at the drop of a hat - black and sooty. Jetting was stock, but she had a 4/1 installed. I wound up going bigger on the main jets as per jetting recommendations. Between that and new stem seals when I reworked the head, no more fouled plugs.

[motoman]

Float levels may be putting it just a tad on the lean side based on your bit of a hang idle. Got a bit of the lean thing going on on my 81Venturer(later carbs)setting float levels way to low in this case. Just was trying to adjust for the 5K elevation and kinda over did it. May be even causing it to flatten out a bit soon on the high-end.....JAT you may consider. Other than that, sounds like your real close to dialing it in!

[TDodge7]

yeah , thats what I don't get , as per the jetting recommendations my bike should need to be richer , but on stock setting it's pig rich , to the point of not even being able to get on the main jet . Nothing was clogged , but opening up the air box bottom and changing the float height helped a lot. Leaning out the main jet a notch helped a lot too , but not quite enough (hence why I ordered some 132.5's to replace those with ) . I guess thats just how this bike is .

[Crazcnuk]

Just for a thought, I would try and drop your needles 1 notch, just to see what it does.

We've had a few here who could not get rid of richness, or poor fuel economy until they did this.

Worked wonders on Derwat's '79SF. Some find it works better then lowering floats, YMMV.

[petejw]

i just finished reading the whole thread,
personally i think your float levels are way to lean,
id reset them on the leaner side of the stock setting (26mm),
float levels affect wot acceleration, the way you have that
set up atm your acceleration will be flat,
Id also go back to stock main jets and as craz said,
id raise the slide needle up a notch.

[Crazcnuk]

I actually said to lower the needles one notch, just to see what it does.

Most people complain of running too rich on these bikes, but it seems to be split into two main groups.

Rich at idle - mid: lowering the floats 2mm seems to get rid of this.

Rich at mid-high w/ poor fuel economy: Lowering the needles one notch seems to take care of this in many cases.

Some people have done both. Some people don;t need to do either.

I am running 2 jet sizes larger than stock, with 2mm lower floats and brand new needles and tubes. My bike is a bit flat at the top end, but I get 40+mpg in town and 45-50mpg on the highway.

Mine is also a full decker so not sure how much of the loss at the top is due to the extra weight and my 750 final drive.

[petejw]

sorry i meant to lower the needle,
to lean the mid range out.

[TDodge7]

but mid range is the only part on mine that feels good , why should I change how it runs at mid when the problem is up top ?

[Crazcnuk]

"Rich at mid-high w/ poor fuel economy: Lowering the needles one notch seems to take care of this in many cases."