05 Vector Inconsistent Idle

[Keith Manning]

Good afternoon everyone. I purchased my first Yamaha last weekend and working to get it ready for this weekend. One thing that is got me so far is a very inconsistent idle. I am syncing the carbs tonight to see how that will impact it, as it was sitting for a year or so. tank has been cleaned. I have not cleaned the carbs but all seem to be working fine.

The problem I am having is at idle 1500ish, you blip the throttle or bring it up to 3,000 and then release it will come down to 2,000 most of the time and then some times it comes down to 1500. when its at 2,000 if you touch the throttle cam it drops down to 1500 as it should. I have released the cable completely to rule out the throttle cable, I have checked for vacuum leaks around the boots and carbs, there are no leaks, it seems to be a sticking throttle plate or weak spring. I really do not want to pull the carbs but has anyone seen this happen or have experience with this.
Thanks
Keith

 

[Metallicat]

These are pretty lean at idle. I used to have hanging idle issues with mine but I changed out the pilots from 45 to 48, and then played with the idle speed adjustment, and also the fuel screws on the bottom of the carbs, and it is much better now.
The idle adjustment knob is very sensitive. Sometimes just turning it a very small amount will solve the problem. You should also clean the pilot jets as they may be gummed up a bit.

 

[Keith Manning]

Thank you I don't want to pull the carbs quite yet. I just got the balancing tool and will do that shortly and see how that impacts it. Thanks

 

[aVenture]

You can sync all you want, (its a good thing to do) but not to cure the symptoms you describe. Those are Constant Velocity carbs and thus the slides are not mechanicaly linked but pulled by vacuum on one side and pushed by air flow the other one. Thing is, those slides have 2 guiding ears which get gummy/dirty and this impact its sensivity greatly for small fine movement.
Your sync guage will show that they don't start to open at same time, one sticking a bit, or such. Do yourself a favor, remove the bellow black cap, inspect the bellow, get the needle out, make sure you count spacer underneat the needle clip, get the slide out.... you will see what i mean with the dirty ears. Clean/polish these first before syncking.
Make sure all 3 carb have good bellows, same spring color, same needle clip positon and spacer underneat. Now you can sync.
You have not dismounted your carb bank thus far. ...just the cap.

Make sure your enrichner linkage is NOT engaged on all 3 before doing ajustments/readings.
Do not size up your pilot jet. Clean it if needed, soaked in carb cleaner overnight at minimum. Dry up do it again with SeeFoam.
Looking from intake side, there is one little hole, this is the air vent for the fuel bowl... it gets clogged up some (at the bowl side) Stick your carb cleaner can and fire in the hole. Fuel level that vary will cause all sort of irregularity as well.