idle mixture problem / colortune issue ? / Going insane ?

[TDodge7]

Ok so here's the deal , my bike has been "just about done" for over a year now , and pretty much the last hurdle that's been holding it up is the idle mixture . But that's so easy you say , I disagree , I've been messing with this thing for months . Now on any of my 2 strokes it's never an issue , run it , adjust the mixture screw , pull the plug and check for tan , done . Granted adding 3 more cylinders can complicate things some , but it should still be a simple matter . So last year I started adjusting everything (I had a jetting issue that's since been sorted out) first I tried to tune it by ear , and I can only say that with my horrible hearing I don't have an ear for it , but I figured I was close . Awesome , so I ride it for a while and check the plugs , some are sooty and black some are white . So the sooty ones get leaned out a little and the lean ones richened up a bit , that ought to do it I thought. I again ride it for a while and the plugs look ok when I pull them so I figure I'm done , I put the bike away . The next time I ride it I decide to pull the plugs to admire my assumed tan plugs , now the other 2 are white and the old lean ones are now sooty ....great . Thus begins the dance where I check the plugs , and make an adjustment , only to have it change again the next time I check the plugs .
So about a million adjustments later I finally decide that I'm obviously too thick to properly opperate a screw so I break down and buy a colortune . I warm up the bike and switch out each plug one by one with the colortune and proceed to adjust each cylinder to a nice blue , then I go for a ride . I quickly realize from all the popping on decel that I'm running way lean ....but the manual said to look for blue . So I look around online and some people say to look for the emergence of yellow , so I give that a try . But all that gets me is more white plugs . At that point I give up on the colortune and go back to making a million tiny adjustments trying to get all the plugs to have (and more importantly keep) a uniform color . Every time I would look at a plug and say that needs to be a little richer or leaner I would make a small adjustment , only to find that the next time I check it it's completely different . This week I finally got to a point where I feel it's running great , really great , and the bike rides awesome , so I figure I must be VERY close to tuned . Just for the hell of it I go get the color tune to see what is going on , all 4 cylinders are orangey yellow ....but here's the weird part , even tho all cylinders show the same color on the colortune the spark plugs don't agree , cylinder #1 sooty , #2 greyish , #3 greyish , #4 white . How is that even possible ??? When I ride it tomorrow I'm convinced that the two middle plugs will have changed their minds and one will be white and the other sooty , but one thing is for sure , TAN does not exist for this xs , I know because I've tried to get it for months , someone please tell me what I'm doing wrong so I can finally stop messing with this bike and just ride it ? I feel like I'm going insane.

[CatatonicBug]

As far as the colortune goes, you're not looking for just "blue". You need to be just on the edge between blue and yellow, IIRC.

[TDodge7]

I did that , it was too lean , it's the closest to tuned it's ever been right now and it's almost orange ...

I've never seen a tan plug with this bike , ever , I saw brown a few times , but when I'd check them a second time they'd gone to sooty or white .

[TomRodgers]

the colortune will set your idle to lower midrange of mix.....that is where your pilot jets come in. the mix screw with smaller jets will have to be 'backed out' more, and 'backed out' less with larger pilot screws.

do all of the carbs have same jets??

to foul/lean out plugs after riding tells me (with my LIMITED knowledge here) that it may be mains that need replacing....or possibly an electrical issue. like you arent getting hot enuf spark for proper combustion.

Any modifications to the bike from stock???

[Ivan]

This week I finally got to a point where I feel it's running great , really great , and the bike rides awesome ,

Then you kept going. You should have just been happy with it running good. If it's running good, why mess with it?

TBH my plugs never have looked right on my scoot. Lately I have really been questioning the gasoline we get lately. Here in KS it really sucks. When a nice slightly rich idle should be right, the bike doesn't run right. I haven't ever messed with a color tune, but have come to the conclusion that, even when tuned on the rich side of peak idle mix, it is too lean. After I installed my Dynojet kit, the instructions said to start with the idle screws out 4 turns, which is an extra 1.5 from where they were. It idles and runs better than ever that way, so I left them.

One other thought would be to try going up or down a step in the heat range of the plugs and see if that gives you a more consistent burn.

[Ken Talbot]

Somewhere back at the start of all this, you must have had the carbs off to check the floats. Do you remember what you saw when you were in there? I.e. - when measured with a micrometer, were all the flaots within a half mm or so of each other, were the left and right lobes of each float at the same height with no twisting, were there any worn spots where the float tab pushes against the end of the float valve, etc?

[Yard Dogg]

Yeah, you should take a scientific approach to these carbs. Assuming the valves are all adjusted right and the spark is good, for setting your floats you should do a fuel level check. You mentioned dirt bikes. I have a kx250 and my xs11, fuel level checks are the way to go. My kx250 is real finicky unless I get just the perfect amount of fuel in the bowl. Measuring your floats will get em cloase to start with, but will not tell the true story of how much fuel is in the bowls, or if all four carbs have the same amount. Once your floats are adjusted correct, the rest will go better. You haven't mentioned syncing. Did you sync your carbs before and after you adjusted your pilots? That's important too. In fact, I would sync, adjust pilots, sync, adjust pilots, then sync once more.

One more thing, I'm having troubles with my pilots too. The 1 and 4 cylinders are affected very little when I adjust my pilots. I've cleaned the living crap out of my ports, so I'm beginning to think the air is leaking past the pilot screws. The nest time I sync and adjust, I'm going to make sure to cap those, and have an extra cap with a hole in it for my screw driver to fit through so the one I'm working on doesn't leak. Be sure your vacuum is leak free.

[TDodge7]

There are no air leaks , tested with starting fluid and an unlit propane torch . all of the floats are set to 27mm ,I have a kerker , k&n filter , one size up from stock main jets, and a drilled air box bottom . Previously I was having a problem where I couldn't go wide open under load , it was the raised floats that made it possible to go wide open , otherwise it was stupid rich and would choke out at 5k and above , but all that was sorted out in a previous thread . The bike runs great , even idle is pretty stable and smooth . I've synched a few times , but like I said I also have adjusted the mixture about a billion times so I'm sure it's due for another one . I just wanted to get it dialed in first , I just don't understand why I can't get tan , or even just uniform grey . If I get it to the point where a plug is sooty I'll start gradually leaning it out , 1/8 turn at a time , but the plug never gets tan , it just goes straight from sooty to white . And if I get a plug that looks like it's halfway between sooty and white then after another ride or two it's gone either to sooty or white . I just don't get it , you'd think that if the colortune is showing a rich burn that I shouldn't be getting any white plugs , I just don't want to assume all is well and grenade the engine by being super lean or anything .

[Larrym]

Delta: Introducing a Change

TDodge7,

JAT...but if your plugs are blackened/sooty right now then at some point in your "stewardship" of the bike, it ran a lot worse, right? I mean you had an initial "rich" problem that took more than just a little time (sweat and tears) to get dialed in.

The plugs indicate what's going on in the cylinders. But where else did all that soot go?? Out the exhaust and into the muffler. Depending on the style/design of the muffler it just may be as sooty or even sootier (Is that even a real word??) Some designs are susceptible to clogging up more than others.

Just for giggles I'd pull off the muffler and if possible remove the baffle/packing to see what's lurking inside. 50/50 chance here.

Back pressure can be fun to watch as someone else tries to figure out WTF is wrong: Or haven't you ever shoved a potato in someones exhaust pipe??

[DGXSER]

When you ride it and get different results, are you riding at different RPM levels primarily? At different RPM levels we use different areas of the carbs primarily.

A while ago, after I first rebuilt the carbs on Thunderstruck, I had screwed up the order of assembly on the needle. So it made my mid to low RPM range VERY rich. As long as I stayed above 3k the engine ran great and the plugs were fine. However, if I let the RPM drop below about 2500 or sat at idle very long, no 1 would fowl out and misfire. I'd clean it up and it would run fine until the next time I let it idle to long or run to low in RPM for to long.

I finally found my error and corrected it and it was like a brand new bike. But I chased that tail for a loooonnng time. But, how they run at diff rpms is very telling in where the problem may be.

[TDodge7]

the thing is it runs awesome everywhere , except maybe for the slight flat spot between 2-3k but so far everything I've read suggests thats the kerkers doing . I'm mainly riding around the neighborhood , lots of idling and low speed stuff . And a few times I've put a box fan infront of the engine and just let her sit there idling . Everything else is good , all I'm trying to do is get the idle mixture good so techincally I don't even need to be riding it around . The main problem is that there is nothing between sooty and white , if i richen it up so much that it gets sooty and then turn it back a slight bit to be somewhere in between rich and lean it just goes lean , then when I compensate it goes too far rich , there's no middle with this thing . If you didn't look at the plugs you'd never know anything was wrong , she starts right up , idles nice , rides great .

[DGXSER]

Have you synched the carbs yet wiht a good vacuum gage of some type? IF they are not synched up, they can do some goofy stuff to each other.

[DenyP]

the thing is it runs awesome everywhere , except maybe for the slight flat spot between 2-3k but so far everything I've read suggests thats the kerkers doing . I'm mainly riding around the neighborhood , lots of idling and low speed stuff . And a few times I've put a box fan infront of the engine and just let her sit there idling . Everything else is good , all I'm trying to do is get the idle mixture good so techincally I don't even need to be riding it around . The main problem is that there is nothing between sooty and white , if i richen it up so much that it gets sooty and then turn it back a slight bit to be somewhere in between rich and lean it just goes lean , then when I compensate it goes too far rich , there's no middle with this thing . If you didn't look at the plugs you'd never know anything was wrong , she starts right up , idles nice , rides great .

If I could get mine to duplicate yours, I'd be hard pressed to change anything and just get out and ride the beast! As long as you aren't lean. I'd put a fresh set of plugs in her, set her where she runs good and go. Don't fuss over the plugs till you have some miles on them.

Deny

[oseaghdha]

Getting your plug color right by dickin with the idle is like, I dunno, cooking based on smell.
The plugs won't color in a helpful manner until you are at speed for a period of time. Plug color is for main jets not idle.

[mro]

I had a jetting issue that's since been sorted out

kerker , k&n filter , one size up from stock main jets, and a drilled air box bottom

all of the floats are set to 27mm

Sorry I never read your other posts so I don’t know all you have gone thru,
BUT if you have 80+ carbs (BS34 III) then setting the floats that high is attempting to mitigate most likely a jetting issue, but you have only gone up one size which with what you’ve posted should not make it so rich that you would have the floats set at 27 to compensate.

Where did you get the jets from? Are they Mukuni jets?
After market jets could be your problem as they are rated different and the “same” jet number as a Mukuni will have different flow etc..

mro