1985 XJ700X just won't stay idling

1985 Maxim X just won't stay idling. Runs like a champ after a complete (minus engine rebuild) tear down and redo. I did have the carbs apart and cleaned them 2x. The bike will start and run on choke but after that you have to crack the throttle just a hair for her to idle. If you adjust the idle, she'll come up but I cannot get it to stick at 1100rpm. I had this issue years ago on an 82 XJ750, and never got it resolved even after cleaning the carbs 4X in a parts cleaner when I worked for a shop. It isn't a terrible problem, but I have the distinct feeling it might be a seal somewhere. I have another set of carbs I am thinking of putting on the bike to see if that rectifies the situation because these carbs required some tlc from the PO (one mixture screw needle was bent on a 90). I really don't feel like tearing into the carbs again. I also couldn't get much of a pull on the mercury sticks for syncing. I had to get the engine to about 2k rpm to get any kind of reading. After reading what Wombat is going through with his bike, I am wondering if I have some bad seals someplace. The bike has 19xxx miles on it and other than this, runs like a champ. I am just tired of holding the throttle open at stops. Any suggestions are appreciated.

 

I had to clean it 3X to get it right. What seals have you messed with? Pull them off and check it again. Make sure the bowl gasket has a good seal. Pilot jet(idle jet).

 

I had to clean it 3X to get it right. What seals have you messed with? Pull them off and check it again. Make sure the bowl gasket has a good seal. Pilot jet(idle jet).

 

I had to clean it 3X to get it right. What seals have you messed with? Pull them off and check it again. Make sure the bowl gasket has a good seal. Pilot jet(idle jet).

 

did you press out the emulsion tubes and clean all the little tiny holes?? and the little hidden passages in the bowls too? Mine idled so-so when I got it, tore into the carbs cleaned and found a diaghram misaligned with the cap. idles good, while I was waiting on paint I took them apart again and this time when I reassembled then it idles great needs very little choke to start maybe 30-45 seconds when cold then choke off and runs very strong. Also have you blown out your airfilter or replaced it? low airflow coming in will give you some headaches as well. I once pinched the oval rubber thing in half was up for whatever reason and I put the seat on that drove me nuts for an hour or so. So it took me 3x to get them abosolutely right. To save some time putting the mixture screws in count the turns to a soft bottom and write it down for each carb.

 

new k&n filter as well as carb to airbox boots. one mixture screw needle was bent on a 90. I have another set of carbs I might try, but I think I am going to pull the plugs and check the vacuum slide alignments before I go through the headache that is pulling those carbs back off. There is another post where the guy (wombat) is going through the identical thing.

 

I would bet you are right about a bad seal (vacuum leak).

Did you test the throttle shaft seals?
I believe the prefered method is using a unlit propane torch around the throttle shafts while idling to see if it changes the rpm.
Both my Xs had bad throttle shaft seals making it difficult to adjust anything.
It's a PAIN to replace them due to the way the butterflies are held in place and you have to break the rack completely apart (carefully keeping track of all the parts). Good thing it they are cheap and will probably last another 20 years.

I've also heard other people test them by spraying some lube on the ends of the shafts when it's running. The vacuum sucks the lube in and it temporarily seals them up.

Also, check for cracked nipples
The caps on the intakes where you hook up the carb-sticks also need to be sealed up properly. Try running it with one or two off and see what you get.

Also, make sure your vacuum line (to the petcock) is not damaged and your petcock diaphram is sound.

I guess you could just pinch the line off and run of prime for a test.

The "couldn't get much of a pull" on the carb sticks isn't a good sign IMO.
You might want to check the compression. I'm guessing it would be odd to have such a severe vacuum leak on all four cylinders.
(at least you would eliminate that potential).

 

Mike, I just went out and pulled the plugs. All looked like white haired elderly men. I believe I had the mixture screws set at 2.5, but I have my doubts. I came out a hair over a turn I believe and now the bike idles and only hesitates slightly coming down from higher in the rpm range. I did a valve adjustment on the intake side this winter and she ran better. If I revved the engine while doing the carb sync, I'd get a reading off them (3&4), but it is really hard to keep one hand on the throttle and another adjusting carbs. I'm going to sync the carbs and put new plugs in her here in the next few days. She idles soundly now at about 1krpm +/- 100rpms right now. I look forward to being able to take her out and see what she does under load. This may just be a mathematical brain fart on my part.

 

Let me know how the bike behaves after you put some miles on it. I had my screws backed out 2 turns and went to back them out another turn and a quarter and, well, ran into some trouble. Should have it back up and running by next week, but I'm curious as to what your results are.