Kind of running. But not good enough to drive

[dig dug mx6]

OK Bear with me as I explain what is happening.
1st after pulling out and clenaing the cards two times determined with the help of others on the site that I had a faulty petcock. Got a $25 rebuild kit and fixed that.
Got a carb sync tool from a friend and sunk the carbs and now is when the funny stuff started.
When I start the bike up it jumps to about 4k in rpm and drops down to about 2k rpm
Now It either idles on 2k or higher or not at all. As I turn down the idle the bike suddenly drops to under 1k and it barley runs then I as I turn it up it doesn't speed up the idle till i give the trottle a twist and rev it and let it drop back down to 2k.
The trottle cable is not stuck it has plenty of free play in it. The carbs are straight across in sync. I am running off an Auxilary tank and have the vacume line for the tank plugged.


Any help on this would be great I have been stumped.

[focus frenzy]

First, do you have the air filter box/pods on it? the carburators wont work correctly without filter(s) installed.
are/is the air filter/ filters clean?
If you do have the airfilter box, or individual air filter pods clean and installed correctly, then the idle fuel cuircuts are not clean enough.
the idle ciurcuts can be dificult to clean due to the very small openings, especialy the tiny holes found in the carburator throught, behind the throttle butterflys ((cv type carbs)

[redliner1973]

Also be advised if you have the CV type carbs, then the 2 middle ones are adjusted with slightly more vacuum than the outer 2.

[Bill + Karen]

Check for a vacuum leak this is a classic symptom of one. Use WD 40 or carb cleaner and spray spairingly around until the motor runs differently. Safe Riding, Bill

[dig dug mx6]

I do have the stock air box installed. I know it needs the correct vacume from having that installed. So the middle 2 carbs need to have more vacume than the outter two. I thought in the Haynes manual the inner two had less vacume? I do have carb sync extensions still installed but capped but it may not be sealed right. Could it be the mixture of the carbs?

[earlfor]

Tim

The vacum on both the early model slide mikuni and the later CV carbs are adjusted with slightly LESS vacum on cylinders 2 and 3.


Earl

Also be advised if you have the CV type carbs, then the 2 middle ones are adjusted with slightly more vacuum than the outer 2.

[dig dug mx6]

ok where should I be spraying to check for a vacume leak? There aren't any vacume line except for the petcock. Unless I have a bad connection between the carbs and air box and carbs and motor.

Also Does anyone know why the breather lines for the carbs would be smoking? Is that a sign of running too rich? If so which way do I turn the mixture screw to adjust this problem I already pulled the plugs that are blocking the screws.

Sorry about my dumb questions but this is my first time working on carbs.

[Anonymous]

Spray around where the carbs meet the engine. I had the same problem on one of my Yamaha's. Bike would start great then race to about 4K at idle! 8O The rubber boots between the carbs were cracked and leaking. I took the one off and went to my local farm supply store. Picked up a foot of fuel line with the same inner diameter as the original boots for about $9. Cut to fit, works fine. Better than payin $30/boot at the stealer.

-Mike