Crazy XJ question for the guru's

[Eric_XJ]

So I rode my bike into work today, just went outside to look at something and notice that there is a brass nipple (assuming for a vac line) underneath the tank that points down towards the carbs that is not hooked up to anything. I left my FSM at home today and wondering what in the hell it's for. And also if it could explain why my bike is holding rpms after it warms up at around 3 grand. Is it for the vacuum advance system ? Or something else. What is it supposed to be hooked to ?

[trbig]

It sounds like you're just talking about the front nipple on the petcocks. Do you have the octo still attached on the carbs? (Mess of lines with a diaphram over the left 2 carbs) If not, the front nipple on the petcock isn't needed. It will flow fuel if you ever turn the petcock to "Prime", or even turn it to run and turn it slightly past straight down towards prime, it may leak. I always leave mine angled just slightly forward to prevent this.

Your bike idling up when warm is usually an indication that the carbs need to be synched.

Tod

[Eric_XJ]

It sounds like you're just talking about the front nipple on the petcocks. Do you have the octo still attached on the carbs? (Mess of lines with a diaphram over the left 2 carbs) If not, the front nipple on the petcock isn't needed. It will flow fuel if you ever turn the petcock to "Prime", or even turn it to run and turn it slightly past straight down towards prime, it may leak. I always leave mine angled just slightly forward to prevent this.

Your bike idling up when warm is usually an indication that the carbs need to be synched.

Tod

It's not on the petcock. It looks like it's under the tank mounted on the backbone. Brass nipple about 1 1/2 inches long pointing straight down towards the carbs. I still have the octo and it's working fine. has all lines attached. Carbs are synced as close as I can get them until I buy a yics block off. They were synced by Yamaha last year after they were jetted before I bought the bike. I have a receipt for the labor and explanation of work performed.

[trbig]

Then yup.. you need to hook a small line from that to the actual nipple on the carb #2. Not the intake boot.. the carb itself. That is your boost sensor and controls your timing advance.

As for a synch.. there's really no way to know if you're close without blocking off the YICS ports. You could be making one good carb even worse, as you drag down a bad carb to what may sound good. A carb synch can last a long time, or depending on several variables, might not last but a couple months. But from what you describe, it's kind of the classic symptom of out of synch carbs and would be the first place I checked. The tools don't cost much, and may end up saving you that much in gas before long.

Tod

[Eric_XJ]

Then yup.. you need to hook a small line from that to the actual nipple on the carb #2. Not the intake boot.. the carb itself. That is your boost sensor and controls your timing advance.

As for a synch.. there's really no way to know if you're close without blocking off the YICS ports. You could be making one good carb even worse, as you drag down a bad carb to what may sound good. A carb synch can last a long time, or depending on several variables, might not last but a couple months. But from what you describe, it's kind of the classic symptom of out of synch carbs and would be the first place I checked. The tools don't cost much, and may end up saving you that much in gas before long.

Tod

Tod,

I know....I gotta order that YICS tool. I was thinking of keeping it blocked off permanently...any opinion one way or another on that ?


Funny thing with that. Carb 2 had a cap on the vac line nipple. Like that when I got the bike.

Here is a pic of the tank line I am talking about.

[trbig]

Well, now I'm cornfuzed..

That boost sensor should be a nipple attached to a litttle black box that sits under the middle of the tank against the left frame rail. I see that's shiny metal??


Tod

[Eric_XJ]

Well, now I'm cornfuzed..

That boost sensor should be a nipple attached to a litttle black box that sits under the middle of the tank against the left frame rail. I see that's shiny metal??


Tod

I think it's from the angle I had to take the pic. I'm about 99% sure that you are right and that is the boost sensor not hooked up. Could that be making my idle hold at 3000 rpm after riding on the highway ? It does settle down after a min or so, but if I pull the clutch to up shift or down shift it holds at 3000

[CatatonicBug]

Can you lift the tank up and take a picture of the top side of where that nipple is? A wider angle might help identify it. I don't know the details of the XJ, but it looks like that thing is mounted exactly where the Reg/Rect goes on the XS. What sits in that spot on the XJ?

[Eric_XJ]

Can you lift the tank up and take a picture of the top side of where that nipple is? A wider angle might help identify it.

Can once I get home. I'm still at work and it was driving me nuts so I had to post and see what I came up with.

[trbig]

any opinion one way or another on that ?

Are you KIDDING me?!? lol.

Every motor I run, I pull the head and block off the YICS ports. I wanna know when I get a bad carb.. not have it limp along unnoticed for however long. Not trying to start a war here, that's just my personal opinion. Sounds like leaving the tool in though would be a much easier option.. just don't know how well the O-rings will hold up over time and heat. Maybe need to pull it out annually or something to replace those??? Maybe someone will chime in that's had theirs in for any length of time, though I can't remember if they've been available for a year yet?

I don't know the details of the XJ, but it looks like that thing is mounted exactly where the Reg/Rect goes on the XS. What sits in that spot on the XJ?

Same spot as the XS.


Tod

[Eric_XJ]

Are you KIDDING me?!? lol.

Every motor I run, I pull the head and block off the YICS ports. I wanna know when I get a bad carb.. not have it limp along unnoticed for however long. Not trying to start a war here, that's just my personal opinion. Sounds like leaving the tool in though would be a much easier option.. just don't know how well the O-rings will hold up over time and heat. Maybe need to pull it out annually or something to replace those??? Maybe someone will chime in that's had theirs in for any length of time, though I can't remember if they've been available for a year yet?


Tod

I was thinking the same thing. It just seems like a poor design choice to me. especially when you need to sync. Way for Yamaha to make more money I guess...

[Eric_XJ]

Looks like one more item to add to the under seat tool storage....extra piece of vacuum hose.


Looking at some diagrams I found on line, I'm pretty convinced it is exactly what Tod thought before seeing the pic. The vacuum timing advance deal....I'll throw a piece on when I get home and see if it gets better.

[Eric_XJ]

Pulled the tank and sure enough it was the vacuum advance line. Smoothed out my idle issues as well. now I just need to adjust the idle mixture. the po had it cranked way up due to the vac line missing and not being able to get it to idle properly.

[madmax-im]

I bought a YICS Eliminator tool from Yahman(Larry) The workmanship is top quality and it comes with a set of replacement O rings...I leave mine in all the time...I have not noticed any ill effect from doing so...its been in there about 1 year...could not be happier as to the way the engine is running..,

[trbig]

Thanks, Ben. I was wondering about that. There shouldn't be any ill-effects from leaving it in. All you're doing is making your carbs pull their own weight, just like every XS out there. You might check on that tool every now and then, just to make sure you still have resistance to pulling it out and that the O-rings aren't getting too flattened. That's great that he put an extra set of O-rings in with it.

Other than that, worst case scenario... the O-rings go bad and the YICS starts operating like it's supposed to? People that say they got a performance boost when either getting rid of the YICS or vice-versa, obviously had/has some carb issues. The only thing disconnecting it does, is make each carb feed it's own cylinder. That's it.

Tod