rebuilt carbs and now it wont idle down

How foolish of me to neglect including "Without a Load" with my caution to not exceed 8,000 rpm's while troubleshooting a Carb issue after installing them and finding that the rpm's are running away on you.

Really.

All you folks with "Home-Dyno's" are safe running it right up to the Red Line.

Silly me!

 

Ok here goes with the xj700 saga. Today I was out working on the maxim and I found that my bro in law who put the carbs on the last time did not get them seated in the boots. This restricted the travel of the throttle so thats why it would not idle down. Once I got them in correctly the bike idled ok. I colortuned them next and found that the idle mixture screw needed to be out about 3 3/4 to 4 1/4 turns out (each carb is a little different) to get a really good blue flame and consistent ignition. The bike idled right down and ran really well, it actually ran the best it ever has. I then synced the carbs using my mercury manometer. I have a YICS blanking tool for this so I know they are all with in 1/16 in of mercury between them. I took the manometer off and put the vacuume caps back on the the thing started right up but wanted to idle at 3000 RPM. Totally frustrated I shut it down and left. My father who was not as frustrated as I was started poking around the carbs and finally checked the header tank I use for working on bikes and it was out of fuel. Can a low fuel level in the carb bowls cause a high idle? He filled the tank and filled the carbs again and low and behold, it idled right at 900 RPM with the idle screw all the way out. So I know it was not touching the throttle linkage on the carbs. I am really ok with idle at 900 but I prefer 1200 so oil keeps flowing to the top end. We will see what tomorrow brings when I go back out to the shop. Hopefully it will idle the same as today. Thanks for all your help guys. I really appreciate you help with this problem. On another note the xj750 carb's I used run this bike really well. I looked at the plugs and they have a nice light brown on the electrode so the bike is running with the right mixture off of idle. I know with these carbs the bike goes as well or faster than my girlfriends xj750 maxim. Thing is a little cruiser rocket.

 

Yes low fuel levels makes the mix go lean and can make the idle high.

Now that you've synced turn the idle speed knob (in the center) in a little to bring the idle up to 1200. Small adjustments and blip the throttle a bit after each movement. Do this with the bike good and warm but be careful not to burn yourself.

 

A 900 Idle is a good sign.
That means you have the Bike's Pilot System really working well.

The test will be how well the Bike "Gets-out-of-the-hole".

Generally speaking, ... an ALL BLUE Colortune will be a smidgeon LEAN.
The Mill might :: Hesitate :: a beat before kicking-in.

If you make seamless power, ... you don't have much more to do.
The Pilot Mixtures should all be good and within just a few degrees of right on the money.

 

Progress report. The xj750 carbs on the xj700 are working great. Ive put 600 miles on the bike and it is performing great. I just checked the plugs last night and they are a nice med brown. The bike idles great and there is no stumble when you start out. I have not checked the gas mileage yet but it seems about the same as my friends xj700 with the correct carbs. So I am confident in letting all you guys on the forum with a xj700 know you can retrofit the more readily available 750 carbs to your bike. You will need to change the butterfly valve shafts over, use the 700 mounting bars and turn the idle mixture screw out around 4 to 4.5 turns. I know some of you wont agree with me but I am just trying to pass along what I have learned. I would rather have put the correct carbs on the bike but there doesn't seem to be any around for a descent price and there are none on ebay, at least not right now. Thanks to everyone for your input and help. It was much appreciated. Now if I can just get my Seca running life would be grand.