XJ700XN refuses to idle

Hi all, I haven't been around much lately, but now that the weather is warmed up, I guess I'm back.

I have been clearing the mothballs off of my X and ever since I took it out of winter storage, there is a weird problem that I just can't figure out. It sat with Sta-Bil in it over the winter, and I started it and let it get hot every three weeks.

It's not dirty carbs.

It starts just as it should and always did before, with no choke at all. It will sit there for about 30 seconds and then *poof* just like you plugged the fuel line, it shuts off. The only way to get it to idle is to put the choke up about halfway, indicating a fuel starvation issue.

Once I get moving, I can turn the choke back off and the engine runs normally. If I stop and it's hot enough, it might rev in the 2k range for about 20 seconds and then shut off. Then it's either feathering the throttle or back on the choke to get it to idle again. If I stop and it's not hot yet, it revs to 0 and shuts off when I pull the clutch in.

The other weird thing is, the idle with the choke halfway on is absolutely perfect. Right around 950 or 1000, smooth and silky, but it does smell a little of extra fuel, and I'm worried about what all this is doing to my plugs.

I've run a whole can of Seafoam through it. The carbs were meticulously cleaned last year. I haven't taken them off this year, but there is just no chance that the carbs are dirty. Not with it starting this easily.

I'm running out of ideas. I tried raising the idle speed, but that doesn't do much. It gets me revving at the 4k range when stopped while hot, but it still shuts off again.

 

Have you checked your inline fuel filter?
Vacuum hose connected correctly? No cracks or leaks?
Petcock in good repair?

You can check Hap's site for more on petcock issues.

I used to own an X and struggled mightily with this same issue. Mine was a cracked vacuum hose, leading to fuel starvation.

 

Hmm... not sure how I did that, but this should have been in XJ Chat. Can a moderator please move?

 

The petcock is in great shape. I did check to make sure that the vacuum hose was connected properly and the inline fuel filter seems to be flowing fine. I suppose the thing to do is install a new filter and some new vacuum hose. It can't hurt and it's cheap.

 

I put on a new fuel filter and line, vacuum hose, and iridium spark plugs. It does run noticeably better and revs faster, but I think that's only due to the plugs. It still won't idle. I guess I'm going to have to take the carbs apart. They look like they're going to be a real pain to remove.

 

sounds like classic plugged or partially plugged pilot jets. It could also be a lazy petcock.

 

They are. Believe me. When I got the X, it was the first thing I did -- I had to. The thing wouldn't run.

The (late) Jeff Mountin, who contributed to the XJCDs, said that he'd gotten the procedure down to where he could have them off in twenty minutes. I call shenanigans.

In the process of cleaning out my own carbs (the needles were stuck to the emulsion tubes!), I took Mr. Mountin's writeup and added pictures, plus my own commentary. I'd post the link, but my filehosting service seems to be down at the moment.

 

No prob. When I bought the bike the PO gave me the XJ cd's.

I haven't rebuilt the petcock yet but it moves smooth as silk and doesn't leak. I changed the vacuum port it was hooked to, but still same result. I think the answer is in the carbs, unfortunately.

 

Well, whaddya know. The site's back up. Enjoy.

 

Woah... comprehensive! Should I soak the pilot jets? Thanks!

 

Heh.

As for setting the float heights, feel free to use something other than the lowly toothpick, as I did. There's a thread around here somewhere on the suggested methodology.

Also of note: Chacal says that the description given in the manual for setting the fuel levels leaves a bit to be desired. They don't actually specify where on the floats to measure the height at. Solution: pick a spot, and use that same spot to measure all four. If the measurement ends up matching the book, great. If not, don't worry, as long as the fuel level ends up within spec.

 

Regardless of how clean the carbs WERE, it sounds to me, based just on what was described, that some of the jets ARE plugged. Regardless of how long it takes you, pull the rack and open the bottoms and check. I've got to agree with Mountin.... I can have a set of carbs off in less than 20 minutes, and I can put them on a whole lot quicker than that. (barring any problems) For those who weren't are my carb clinic back in early June, I had put a set of carbs back on an xj750 seca for listmember jgb1503, and I had them on, all boots tightened down, and hooked up in about 5 min (or close to that.........Josh, you were standing there, you saw it happen!!) I'll pobably NEVER be able to do that again, but it doesn't take a ridiculous amount of time after you've done a few. Usually it's about 15 minutes or so. Go methodically and don't get impatient.... THAT is what makes things take a long time.

FWIW,

 

On a Seca, perhaps; a Maxim-X is a different animal. Things are much more crowded in there. As the original text described, even finding room to wiggle them out of the manifold boots can be a challenge.

 

Agreed. I could have the carbs off and back on my old Seca within 30 minutes and I still haven't summoned up the willpower to take these off the Maxim-X. Maybe next weekend.

 

I can get my carbs off in about 10 mins...I've had too much practice. To get them back on I use two hammers...not that way, I use the wooden handles from the front side of the air box after I have them started or aimed up to the manifolds, just work those suckers in with the ends of the hammers.

 

OK so we need one of those NASCAR style pit crew contests to see how fast we can get the carbs out/in. :lol:

It is an unfortunate side effect of having to mess with them so much that we get so good at it.

I was helping a member with his bike this weekend and I think we had them in/out 3 times. :twisted: