96 xvz13ah multiple questions - backfire - coolant leak - carb sync/vacuume guages

[Marcarl]

Did you set and clean the needles yet?

[Berdman]

1 hour ago, Marcarl said:

Did you set and clean the needles yet?

I pulled one needle (pilot screw?) completely out last night. The needles are all new, and the carb looked spotless. The guy who rebuilt it soaked it twice in an ultrasonic bath. There might still be some gunk in it? 

[Marcarl]

Let's put it this way. If everything is hunkie dorrie, then when you adjust the idle mixture screws there should be a change in engine rpm. You say that's not happening, well then things are dorrie hunkie. Seeing as the idle mixture circuit is hard to clean, I can understand that many times the side port is not cleaned in the rebuild process, yes the port going into the throat of the carb gets cleaned, and that is what you can see, but you can't see the port on the side. If that is plugged or restricted, the idle mixture screw will have little impact.

Just for fun let's go over this again. Balance the carbs to perfection, not to the point of 'good enough' or ' that is the best I can do' , you want them all at the same vacuum level. Now with the gauges still attached, play with the idle mixture screws. Gently turn them in until the vacuum starts to drop, then back them out and you should see the vacuum come up, keep backing them out until the vacuum goes down once more. The half-way mark between the changes is the sweet spot. If you have no change in vacuum then the idle mixture circuit is not working.

[Berdman]

5 hours ago, Marcarl said:

Let's put it this way. If everything is hunkie dorrie, then when you adjust the idle mixture screws there should be a change in engine rpm. You say that's not happening, well then things are dorrie hunkie. Seeing as the idle mixture circuit is hard to clean, I can understand that many times the side port is not cleaned in the rebuild process, yes the port going into the throat of the carb gets cleaned, and that is what you can see, but you can't see the port on the side. If that is plugged or restricted, the idle mixture screw will have little impact.

Just for fun let's go over this again. Balance the carbs to perfection, not to the point of 'good enough' or ' that is the best I can do' , you want them all at the same vacuum level. Now with the gauges still attached, play with the idle mixture screws. Gently turn them in until the vacuum starts to drop, then back them out and you should see the vacuum come up, keep backing them out until the vacuum goes down once more. The half-way mark between the changes is the sweet spot. If you have no change in vacuum then the idle mixture circuit is not 

Will try the cleaning procedure tonight when I get home. Fingers crossed that's all the issue is. Would really like to not pull the carb off again. Thank you!