Can anyone help me diagnose this? (Video)

MILLENNIUM FALCON

MILLENNIUM FALCON

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This bike is an 81 xs400 special. I also posted this in the build section but I dont think anyone is going to read it. Here is the low down. I am having some fuel issues. I went over everything today. The carbs are clean and all parts pass visual inspection. I have good spark, and the plugs look fine. I had a bad miss on the left cylinder. It had spark but wasn't getting fuel. I know this because the plug was cold and dry, The header was about 100 degrees cooler (inferred temp gun) than the right header,I could pull the left plug wire off while it was running and nothing would change, but if I squirted some carb cleaner in the left carb it would pick up and smooth right out. the carb bowl is full of gas but it doesnt seem to be getting into the intake. I pulled the carb again, but I couldn't find any problems. Now when I start it up it seems to be firing on both cylinders, (most of the time) header temps are much closer, but now it wont idle. In the video I start the bike and it climbs up to 4500rpm, when I blip the throttle it climbs but wont go below 4500. When I pull the choke out it goes down to 1200rpm. Can anyone give me any direction on this? Thanks.

http://www.youtube.com/watch?v=0B_36F62G04
 
Check for sticking slide.

Sometimes, if a slide is sticking open, you can whack the carb with a rubber mallet, and the slide will go down.
 
I thought it might be that, so I watched the slides while it was running. They both were in the same position. I did check for vacuum leaks but didn't find any. i'm sure its something stupidly simple, but its driving me nuts!
 
Is you throttle linkage hanging up? I was stumped on something similar on a bike for weeks... Turned out he cable I was using had housing that was a couple mm too long... I know. Stupid! But it happened... And I was cleaning, re-jetting, awww.... I had those carbs of the bike like 10 times before I figured it out.
 
i would imagine you tried to lower the idle? valve clr's ck'd? everything installed correctly! if all ok it is running lean (idle)...ck low speed circuit jets...does that have a air cut off diaphragm? with it idling high with the choke in have you tried to adjust the low speed mixture screws? do they both have the same effect or possibly only one makes any considerable changes in speed? any chance the sync plugs are missing ? hose for vac petcock bad/off(if it has one)...inlet airleak? ck with contact cleaner and see if idle changes while running...hopefully that will give you some help...
joe@ v cycle
 
I will check to see if the cable is hanging up. I did try to lower the idle, but it is so sparatic i have ruled that out. I didn't check the valves yet. I did check compression. 153 on the right 150 on the left. The sync plugs are on. have checked for leaks with carb cleaner. I will try the low speed screws. I have never worked on these exact carbs before, so im sure im missing something. I really feel like it is running lean. I will let you know If how I make out.
 
Ok.......I just tried to reset/adjust the mixture screws. they had little or no effect. The cylinder on the left side just isn't getting fuel. It seems to pick up at higher RPM so I think it may have something to do with the slow jet. I' just guessing at this point.
 
Good Guess. It sounds like the slow (pilot) jet is blocked or the tiny holes it feeds are probably blocked. There are two or more tiny holes in the throat of teh carb close to the butterfly and they can be full or corrosion or dirt. blast a can of carb cleaner through from the slow jet and see if both carbs spray similar amounts. My guess is that the left is blocked.
 
yea that is why i wanted to see if you had one side that the mixture adjustment made a difference...if it does then the circuit is more than likely open and operational and the one that has no change in speed is blocked...you need to be positive that all idle circuits and jets are open..good luck and keep that carb cleaner out of your eyes......joe@vcycle
 
So, I bought a big bucket of carb cleaner. I completely stripped the carbs and now im soaking the bodies. Hopefully that will take care of any left over grime.
 
And you will blow through all those tiny drillings to test both carbs won't you?

I had a set of CB160 carbs that were dunked in the ultrasonic cleaner twice and one was still blocked above the pilot jet. It too forever with a bent piece of lock wire to clear it out.
 
Yeah I have some aerosol carb cleaner as well. I have some spray gun cleaning wire I will use too. Those suckers are going to be clean and clear!!
 
Re: Can anyone help me diagnose this? UPDATE

Ok now i'm mad. $30 on cans and buckets of cleaner. Soaked the carbs all night, meticulously cleaned and reassembled. Now when I run it, it idles ok, but is still running on one cylinder. (Same as before) So, im thinking maybe its not fuel. I am noticing that The plug wire is shorts out to my finger when I touch it, so I thought maybe it just a bad plug wire this whole time? So I out on a spare plug wire I have from my parts bike, and it is still shorting out to my finger. I electrical taped the entire wire plugs, ends and at the coil. IT IS STILL jumping to whatever is around it. Is my coil leaking or something? Now i'm thinking its a spark problem. Im going out to switch the plug wire from the side I know is working. Any clue??????????????? I'll be back in a few..
 
Re: Can anyone help me diagnose this? HELP!

Well that was a waste of time. I swapped wires and coils....no change. I cannot get the left cylinder to fire. I checked the valves and compression and it passes. I changed plugs too. I have a very strong spark. Is it possible one set of points can be so far off that it wont fire, but still show a good spark? I cant get any consistency so it hard to fix it through process of elimination. Now when I start it, it idles ok but If I touch the throttle it revs really high and just stays there (5000) I checked to make sure it wasnt the throttle cable, its not.
 
I know no one is reading this but I still need help

I finally got the bike running on both cylinder! but I still cant get it to idle. It runs up to 5000 rpm as soon as I hit the starter button. The weird thing is the butterfly's are closed and the slides are all the way down. How is that possible? I tried spraying carb cleaner on everything when it was actually idling (1100rpm) to check for vacuum leaks, but it did not change the engine speed. I also used a propane torch. It seems like it has to be getting air from somewhere. Dont ya think?
 
These are CV carbs? Can you actually see the slides all the way down?

I haven't read back through all the posts, but before tackling carbs, you should always make sure the valves are adjusted properly and timing is perfect. Bike doesn't need to run for those. If the bike is running, throw a strobe light on it to check the timing accurately.

All that being done, then it's syncing the carbs. If they're out of sync, you'll get the racing idle.
 
Tim, They are mikuni's. I can see the slides sitting on the stops by looking in the back of the carbs while it's running. The valves are adjusted. I do need to check the timing. I want to sync the carbs, but I'm afraid to hook up the sync pro beacuse it will suck my fluid right out of it. I can't get it to run below 4000 rpm.
 
I was confused by that last post, so I had to read back through pages of thread to make sure I had it clear. We are talking stock/OEM Mikuni BS series carbs yes - not VM32 mikunis as I understand it. I thought that stock carbs were Keihins, so that's why I want to be clear what we're dealing with.

If that's the case, the issue is probably not the slides which are "vacuum" operated, but it may be an issue of one or other "butterflies being open too far. Pull the carbs again and see how open the two throttle plates are. The way the two carbs connect, it's possible to have one too far open relative to its partner.

There are two simple ways to do a bench synch. One is to use thin wire under each throttle plate and twist the twistgrip and see if the wires move at the same time. The other way is the way that Suzuki recommend for some bikes and and that's to look at the bleed holes to see that both sides start to uncover the bleed holes together. (Not sure what Kawasaki recommend for bench synch.)

If both carbs are actually opening together, then it sounds like an air leak into the intake manifold from a crack or bad seal to the head.
 
Sorry If I Was confusing. They are vacuum slide mikuni. I did sync them with my prosync. I have checked the butterfly operation. I found that the PO never replaced the o ring that goes under the mixture needle. I didn't even know there was supposed to be one in there. I replaced them and now it runs better but still not right. I will try to get some pictures for you guys. Thanks.
 
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