83 xj750 idle problems

Listen guys, been a lurker for the past month or so. Bought an 83 XJ750 for 500 bucks, and since then I have invested a good amount getting it back to spec... added a master cylinder, replaced calipers, fixed the rear brakes, fixed a lot of body-related things, and got all the lights working. Physically the bike is complete. I cannot for the life of me get it to run right.

Here is the deal and I will be honest... I have not done the first commandment... I have been chasing what seem to be vacuum leaks. replaced throttle shaft seals (OEM from xj4ever) and replaced carb boots.... carb boots still leaked so used Rtv to get that sealed... I have taken the carbs to church following the community guidelines (ultrasonic, simple green)... replaced diaphragms, and o rings, and done the rebuild... I am a career mechanic but new to motorcycles...

The carbs seem to check out...

I have been struggling with it "running off" and as I have fixed the vacuum leaks it has seemed to improve.... but tonight after sealing everything (no known vacuum leaks at this time) it is idling high... I can back the idle adjustment off (butterfly's closed and she still wants to run)..... am I still chasing down vacuum leaks? cylinder 3 seems wet...

am I a sinner and should I check valves asap.... could valves out of adjustment cause high idle....?

I have an entire second engine and frame... I have married myself to this bike... but I need to ride...

Looking for expertise. I will give you any info desired...

I am so desperate to ride I was pondering getting a 2009 vulcan 500 in good shape just to ride.... willing to pay to play, but ultimately want to conquer this XJ!

 

Welcome to the forum. Yes them carbs can just about drive a person nuts, been there on them. An ultrasonic cleaner will not clean the very small jet in the bottom of each float bowl. That jet is the enrichment ckt and cause all kinds off issues. Using a small wire, a bread tie, works good when you strip the insulation off it, and compressed air. I have spent up to 20 mins on one jet to get it opened up enough to make B-12 chem tool through it.

You did do a bench synch on the carbs? Need to have that done as well as a good wet set. Sounds like you are very close to being there. Just know that these carbs are a bugger to get clean until you know the ins and outs of what to look for. Not like other carbs on a Honda or some other bikes.

Did you do the compressed air test to make sure that your diaphragms are sealed and lifting the vacuum pistons up? Shooting a little bit of compressed air into that upper oval opening on the air intake side will show you if the vacuum pistons are moving up and down as they should.

 

Bench synch, using the edge of hole method - assumes you've been careful when you bolted in the butterflies - ie they are set right on the shafts?
Building, or rebuilding these carbs is easy once you appreciate one thing - attention to detail...