Throttle shaft seals

Just when all was well and riding was a joy...behold the leaky throttle shaft seals.

So, my question is actually in regards to the fuel feed tube o-rings. I replaced them when I did a carb clean last year, but I'm worried that if I have to pull the rack apart to redo the throttle shaft seals, will the one-year-old o-rings need to be replaced again?

And, as I'm contemplating how much of the carbs I will have to take apart to put these new seals in: I'm hoping I don't need to take the caps an floats apart again (re-did those last year as well). In fact, had rebuild kits sent from Chacal, basically did everything but the throttle shaft seals.

Thanks. Hope everyone's doing some good riding in the meantime.

 

Feed tube o-rings should still be OK; you will need to pull the "hats" because you're going to need to get the slides/needles out of the way. Since I believe the "X" has Mikunis, you'll be doing some filing so I would recommend they come all the way apart so you can ensure no errant filing debris has gotten anywhere it shouldn't.

While you might be able to get away with some rag-stuffing to keep the bottom ends clean during the process, I wouldn't take any chances.

 

Thanks, Fitz.
When you say filing do you mean to get the old shaft seal material cleaned off the carb body?

 

The filing is because you have to pull the butterflies out in order to get to the shaft seals, and the butterflies are held in by screws which are peened over at the factory in order to prevent accidental loosening. Those mooshed threads have to be removed before you take the screws out or you run the risk of damaging the female threads in the throttle shafts.

There are a couple different methods of removing the deformed threads, but here's how I handled it:
http://www.xjbikes.com/Forums/viewtopic/t=17628.html

Burnarr

 

Ah, I see. My ass is suddenly anticipating more pain.
Ok, we'll see how this goes when I get to it. Thanks for the advice.

 

Haha! Yeah, the actual act of removing the shaft seals is probably the easiest part of the whole job. Once you get the peened screws, butterflies, and throttle shafts out, the shrunken dried out shaft seals will probably simply fall out of the carb bodies onto the floor. :lol:

But actually getting to that point? That's a bit more effort.

 

Just out of curiosity...
What symptoms are you experiencing, and how have you isolated the source of your trouble?

I'm getting suspicious of my seals, but it might just be hypochondria...

 

Ikarus,

I see gasoline seeping out of the sides of the seals, can smell gas, hanging idle at times. If you're running lean plus all of the above, I would take a look at those seals.

 

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I see gasoline seeping out of the sides of the seals, can smell gas, hanging idle at times. If you're running lean plus all of the above, I would take a look at those seals.
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gasoline would not leak out of the "throttle shaft seals" , that would be the fuel rail seals, different animal.
leaking throttle shaft seals , would be "sucking air in".
(under normal running conditions)
stu

 

Sorry to resurrect this old thread from the dead but I feel like I'm chasing ghosts over here.

I've got an 84 Yamaha FJ600 that I picked up a while back for what I thought was a fair price. I've always loved the style of these old sport bikes and if I could add one to the collection for a fair price I though, why not?!

The bike was half torn apart when I picked it up but as the famous old saying goes... "it ran fine prior to taking it apart".

Long story short I've given the bike a good go over, sourced the parts I needed and over the past few months, have slowly put it back together.
Rebuilt the carbs and have them roughly set to give me a decent starting point. My issue now is when i fire the bike up. It instantly revs up to around 7 thousand rpm and I have to shut the bike off. I've changed the intake manifold boots and gaskets as they had some dry rot but that made no difference. I know there's an air leak somewhere and I'm beginning to think the throttle shaft seals. Am I on the right track?

 

Could very well be. When you rebuilt the carbs were the seals stiffish?

 

You just need to set them "roughly" a bit more closed with the idle speed screw, that's assuming you bench synced the something like correct of course.
Air on its own won't make it run fast, it needs fuel as well. Take the carbs off, check the bench synch, check they close fully, then give the idle screw half a turn in.
When you put them back on, check both cables work as they should (assuming you have a "choke " cable?)

 

I think you deserved a thread of your own. Having gone thru carb rebuild and startup, lots of this is fresh in my memory.
Couple things to look at :
1) run off a separate tank so you can see what is going on with the carbs. Like this thing. You really need this to run sync the carbs anyway.
https://www.amazon.com/gp/product/B08YMX4NWK
2) If you did not bench sync the carbs, go back and do so as recommended. You should also test the wet float levels if you have not done so at that time.
3) make sure when you lower the throttle, the the cabs are all going back to idle position. Look at what a fully closed throttle looks like while on the bench. That can tell you how far off the idle screw is. when its set.
4) If you are starting it with the choke (fuel enrichment lever), does returning it to the off position (fully right) lower the choke plungers on the carbs?

Good Luck.

 

I doubt it - sure you haven't just snagged the the throttle cable up - easily done.

 

when reinstalling carb rack this happened to me. - just another thing to think about.