Colortune conundrum with Mikuni BS34 Carbs

My initial foray into adjusting the fuel/air mix but knowing I don't have enough time left this year to do the rebuild. I just want to get it running better for the next couple of weeks and then park it for the winter.

So... I just put the colortune to the XJ1100 and I can't understand the results I'm getting. On the XJ650 with Hitachi carbs, when I use the colortune I can get a definite Orange color through pale blue so I have no question when I have it set properly.

On the XJ1100 with the Mikuni BS43 carbs, all the idle adjustment screws were tightened down by the PO as far as possible except Cyl #1. I used Kroil (Thanks for the suggestion BigFitz!) Nowhere was I able to turn the screws and get any orange color change whatsoever (It's always a shad of a blue color) yet I could hear definite engine changes . I finally decided to use the semi-arbitrary 2.5 turns from closed setting and put the colortune away.

The bike seems to run lean in that it popcorns through deceleration. I looked at the plugs and they are very white at idle, they're new and the old plugs were pretty carboned up. Running butane around the carbs does nothing to change the RPM. I'm looking right now at idle, not looking at what's happening under highway speeds & I don't think plug chops will clue me on any idle issues?

It looks to have a 4-1 MAC exhaust but stock air filter. Coils are Green Dyna.

So... any idea why I can't get any orange even when the idle adjustment screws are all the way in?

Thanks,

 

Your last sentence is a bit confusing - - you get the orange/yellow when the screws are too far out.
I can only guess that your Pilot system is a bit plugged.
You have months to fix it.

 

LOL! there is much I say that is confusing. Yes I should have said all the way out.

I'm just amazed I can't get any orange no matter where I turn the idle screw.

 

You cant dodge it, if the pilot mixture screws (not idle adjustment screws) have no effect the carbs need cleaned & re-sync.
When the carbs are cleaned & set up properly the smallest amount of rotation will produce a result.

 

So... any idea why I can't get any orange even when the idle adjustment screws are all the way in?
To get orange/ yellow color you turn the pilot screws out not in. Turning screws in reduces the amount of fuel turning the screws out increases the fuel Try running some berrymans ride through a tank of fuel fill up with fresh fuel and colortune again.

 

You're not getting any effect running the screws in and out because the pilots are plugged. THAT plugged will most likely require more than just trying to run some carb cleaner through.

 

Yes, that appears to be the answer then. If it weren't for using Chacal's idle adjustment screw tool I wouldn't have been able to get to turn those screws, the PO had them screwed in to the bottom & tightly. Last night I put a drop of Kroil in each screw recess and will see if that makes a difference today. I'm guessing they will turn more freely & maybe it will help clear out varnish. I did put over 1/2 can of surfoam into a full tank of gas and ran it to near empty & then refilled with 93 octane. It was then I tried the colortune.

Pretty much academic I guess, soon it will be time to bring it inside and start the long going over it from top to bottom. A complete carb cleaning, ultrasounding the bodies & synching will be done.

I have been making a list of things that must be attended to during this hiatus & all these answers are a help toward my understanding of what is going on.

Thanks

 

Since you have the luxury of time as it's a "project" bike, just be methodical and go through absolutely everything tiny bit by tiny bit just like Wiz does.

Going through the whole bike can be a lot of work but it's also a lot of fun and you learn a lot in the process that's for sure. I know I have.

I use the "maintenance" section in the factory book as my "flowchart" as it were, but take each step further; cleaning, restoring, painting and polishing along the way. Nothing goes back on until it looks and works like new.

It's really rewarding to start out with a scruffy runner and end up with a showroom clean bike.

 

If they were tightened down hard, The pilot screw tips may be broke off and stuck in the carb body. If so, any adjustment you make wont change anything.

Only way to tell is to pull the carbs as they may need a good cleaning anyway and remove the pilot adjust screw. See if it still has the tip on it or if it's stuck in the carb body.

I had a couple tips stuck in the carb body on a few. I disassembled, thoroughly cleaned them and set them in the deep freeze for a couple hours. When I pulled them the tips pushed right out. Make sure you have them upside down and the pilot screw removed so the tip falls out and not back into the idle circuit.