Revs won't drop...

[Senator_Kang]

Hello!

The saga continues with my FJ. The story so far (apologies if this is lengthy, but I don't know what is relevant):
- Bike was sitting for a only a few months before I got it
- Ran alright, but a bit rough, on the ride home
- Became harder to start over the next couple of starts
Then:
- Wouldn't start at all, but then fired right up later on that afternoon
- On the ride home it was very rough. It would idle alright, but with light throttle it would sputter and almost die until it caught on and nearly threw me off the back/into the car in front
- Didn't want to start at all after that

Here are the things I've done so far:
- Pulled the carbs and cleaned them out as best I could. I figured that since I (ahem) dropped it on my driveway a bunch o' crap might have gone all in there.
- Replaced 2 pilot jets which were all caked up
- Replaced the choke cable!
- New plugs
- Replaced one needle and one seat and one o-ring (all on different carbs!) which were dodgy

The bike now starts like a champ! First stab of the button. Awesome!

Alas, problems! When it's cold and you gently twist or even just apply pressure to the throttle it hesitates; you can hear the sound change but the revs don't rise. Then, like before but FAR more gently, it jumps up to about 2,000 with no further throttle. This doesn't seem to happen with a good rev. Give it a good rev and the revs fall quite slowly after lingering up there.

When it's warm the hesitation from idle on tiny throttle openings is the same. But! Give it a rev and they *won't come back down*. Rev to 3,000, throttle closed, it still sits at 3,000. Doesn't seem to matter where you rev it to, they just stay there. Kill it and start it up again, and it goes right back to idle.

Here's what I've tried so far:
- Used the search function 
- Decided it's running lean. Tried various settings, tried to read plugs (got all to be a nice grey except for #3 - black  ). Revs are still slow to come back down when cold but much richer and there is black smoke/haze

- Decided the problem when hot is due to a vacuum leak
- Checked the 'ignitor' box. The diaphragm inside won't hold pressure at all when I blow through it. Pulled the hose off, 'sealed' with a screw. No help.
- Looked for other leaks, in the manifold maybe? Sprayed carb cleaner around: nothing.
- Put some nice new big hose clamps on the manifolds. Nope. BUT! I did notice a groove in the carbs where they go into the manifolds. Is there supposed to be an o-ring in there? Would it really leak through there even with the nice new fat hose clamps screwed in as tight as I can get them?

I really am puzzled. I hope it's something stupid simple like the manifold o-ring possibility. Ideas for either problem?

[giantkiller]

If had the same problem with high revs when hot did same thing. Sprayed around the intake with starer fluid. Then tried water. Thought maybe it might seal it. Did both several times. Nothing so I cleaned the carbs several more times. Had already rebuilt them with Randy's carb kits. Randy in his wisdom includes intake orings in his kits. So even though spraying around intakes made no difference. I installed them... Fixed it no more hanging revs

[movenon]

Sounds like you still have a carb problem.  Sometimes hard to trouble shoot via the WEB.  As giantkiller said I always recommend to anyone that pulls there carbs off to clean,  replace those intake O rings (and inspect the manifolds).  The O rings are cheap and they do get old and fail.  My #3 had been "repaired" by a PO.  He just gooped it with silicone and reassembled.  I discovered it during my carb rebuild it wasn't causing a problem but it wasn't the way to fix the problem either.  

Before you pull the carbs take a good look at the choke pistons when you pull the choke. Do all 4 reseat all the way in with the choke off?  Are the choke pistons on the carbs snug?  Throttle cables, do they let the carbs return back to the idle position every time? Are the cables routed correctly?  Vacuum hose or hoses, good shape?  Old or brittle then just replace them.  Cheap.  Make sure your fuel air screws are all correct,  screw, spring, small washer and the all important small o ring.  And that there isn't an extra O ring stuck down it the hole... Details count.

When we talk about cleaning or rebuilding carbs it is hard to judge at what level it was done at.  From your description the carbs sounded pretty dirty when you got them.  You might have to go back and go through them again.  Totally disassemble them, emulsion tubes, jets, choke pistons etc.. At a minimum clean out every orifice in the carbs with carb cleaner and compressed air.  If you know someone with an ultrasonic cleaner that wouldn't hurt.  Not required but nice if you can.  Even with that clean and with compressed air blow/clean out every passage way.  Best advice I can give in cleaning carbs is take your time, do it in a clean area, inspect every detail, the files section has a couple of good write ups on carb cleaning.

Where are you located ? Is there another FJ owner in the area that can give you a second set of eyes or help ? As a suggestion in your signature line it helps if you put the year of bike that you own. There are small differences between FJ's and the information helps in trouble shooting.

I don't know if any of this helps, but hang in there. It is fixable and is probably a simple problem in the end, you just can't see it yet. But you will  
Keep posting as you try things.
George

[FJ1100mjk]

In early summer, I had the carb bank off my '85 and removed the intake manifolds. I had them off already in the not too distant past, and had replaced the o-rings with those that are supplied with this kit http://www.rpmracingca.com/proddetail.asp?prod=carbkit&cat=39 I was surprised to find that they had taken a permanent set (flattened, with no rebound evident, even after they sat for days), and were suspect to an air leak. I didn't have a new set of o-rings laying around, but I had this http://www.permatex.com/products-2/product-categories/gasketing/gasket-makers/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker-detail that I used with success on my Kawasaki's intake manifolds that do not use an o-ring for sealing, and where there was clear evidence that air was slipping by un-checked. I put a thin layer of the sealant between the manifold and the cylinder head interface, torqued the screws to spec, waited a couple of days, and continued with the rest of the work. Can't say what would happen over time with just o-rings used for sealing, but the sealant was employed for assurance.

[movenon]

In early summer, I had the carb bank off my '85 and removed the intake manifolds. I had them off already in the not too distant past, and had replaced the o-rings with those that are supplied with this kit http://www.rpmracingca.com/proddetail.asp?prod=carbkit&cat=39 I was surprised to find that they had taken a permanent set (flattened, with no rebound evident, even after they sat for days), and were suspect to an air leak. I didn't have a new set of o-rings laying around, but I had this http://www.permatex.com/products-2/product-categories/gasketing/gasket-makers/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker-detail that I used with success on my Kawasaki's intake manifolds that do not use an o-ring for sealing, and where there was clear evidence that air was slipping by un-checked. I put a thin layer of the sealant between the manifold and the cylinder head interface, torqued the screws to spec, waited a couple of days, and continued with the rest of the work. Can't say what would happen over time with just o-rings used for sealing, but the sealant was employed for assurance.

I am sorry I didn't mean to say not to use a proper sealent.  In my case 3 manifolds were as stock (no sealent) and one was siliconed.  It indicated to me that it was a limited repair.  Going through all that work just to silicone one cylinder manifold seemed to be a mark of a poor repair considering the o rings are cheap and at that point all should have been replaced IMO not just one. Quiet possably the PO didn't even replace that one with a new O ring...

I could understand if the cost was high then one might elect to do a limited repair.  And you are correct, those O rings end up flat and will probably never be round again. 

I am reasonably sure adding a proper sealent with new o rings in the manifold will do no harm. I Just wouldn't waste time sealing one flat o ring and throwing it back together.  Details.... Same with the carbs. 
George

[FJ_Hooligan]

Did you remove the little clips that pull the choke plungers?  If so, then do a check of them.  One is different than the others.  If it gets installed on the wrong carb it can hold the other plungers slightly open and cause an air leak.

If it's reving up, then it's getting air from somewhere. 

[Firehawk068]

It is not advised to use any kind of RTV silicone on any part of the intake system, or anywhere that there is a possibility of coming into contact with fuel or fuel/air mixture.
All of the RTV sealants that I know of will dissolve from fuel contact................

If you have used it previously, you may have been lucky................But be warned! Do not use it on the intake manifold boots!

[FJ1100mjk]

It is not advised to use any kind of RTV silicone on any part of the intake system, or anywhere that there is a possibility of coming into contact with fuel or fuel/air mixture.
All of the RTV sealants that I know of will dissolve from fuel contact................

If you have used it previously, you may have been lucky................But be warned! Do not use it on the intake manifold boots!

Thanks for your warning on silicone and fuels. Duly noted for all.

I am aware silicone being non-compatible with gasoline and I have brought it to someone else's attention here a few month's back.

See last three posts in this link:

http://www.fjowners.com/index.php?topic=11613.msg116077#msg116077

I don't advocate its usage as a fuel line material, or trying to seal a rust hole in a gas tank, but for me and how I have used it, it has worked for years on the Kawasaki application, and thousands of miles on my FJ.

I don't see a lot of potential for the silicone's erosion/deterioration due to its small surface area in contact (it's like what .002" thick?), and with a fuel mixture that is 13 to 14 odd parts air to one part gas.

[Senator_Kang]

Thanks for your replies!

I've confused myself a little though. I was thinking an o-ring might belong in the little recess there on the engine side of the carb:



^ I don't know if that's a picture of our carbs, but you get what I mean


All the 'intake manifold o-rings' I can find seem to go between the manifold and the head? Is there supposed to be one on the carb there? I'm a little reluctant to clean out the carbs again if I don't need to, but you gotta do what you gotta do I guess...

[FJ1100mjk]

No o-ring in the area that you have highlighted in your graphics of the carb.

If you haven't seen this PDF document, it will help if you are going to go back into the carbs for another inspection and cleaning:

http://www.fjowners.com/index.php?topic=12098.0

[movenon]

With the carb bank out,  remove the aluminum heat shield then remove the intake manifolds that bolt to the engine. The large o rings go between the manifolds and the head.  Inspect the manifolds for cracks, install the manifolds carefully don't over TQ them.

Here is a picture of the manifold and o ring grove
http://yamaha-parts.victordrummond.net/fj1100-fj1200-xjr1200-xjr1300-engine-parts/carb-inlet-o-ring-93210-40659-00

Here are the o rings.
http://www.rpmracingca.com/proddetail.asp?prod=Carb%3AIntakeO-Ring&cat=24

If you plan on removing the manifolds then get the o rings in advance.  Don't reuse the old o rings.  If you bought an o ring kit from Randy then there were probably 4 new large o rings that you didn't install, that would be the ones..

As noted from fj1100mjk I would also advise you to take some time and read that PDF.  Read it until you understand each step clearly before you get into the carbs and have the article handy as you clean or rebuild the carbs.  Take your time with the carbs if you rebuild them.  Simple as they are,  missing one little detail can cause you a problem.
George

[FJ_Hooligan]

All the 'intake manifold o-rings' I can find seem to go between the manifold and the head? Is there supposed to be one on the carb there? I'm a little reluctant to clean out the carbs again if I don't need to, but you gotta do what you gotta do I guess...

That groove in the carb that you've highlighted mates with a rib in the intake manifold.  When the groove seats in the rib, that means the carbs are installed in the manifolds correctly.

[Maticuno]

Occasionally my revs hang in the 2 - 3k range.  It's from the choke sticking on.  As this is happening, gently pull back the left side cover at the front where it meets the gas tank.  Feel around on the carb for a little bar sticking out.  Give this a gentle push back toward the center of the bike and it will close the choke on all of the carbs.  Make sure you do this after attempting to turn off the choke at the handlebar switch.

[Senator_Kang]

That groove in the carb that you've highlighted mates with a rib in the intake manifold.  When the groove seats in the rib, that means the carbs are installed in the manifolds correctly.

I see... I just shoved them in as far as felt right. I'll take another look at that, because it's very likely they're not seated correctly.

If that doesn't work, I'll grab the 4 o-rings from Vic Drummond as he is just a little north of me then tackle the manifolds.

If that doesn't work, I'll grab a beer and get stuck into the carbs again. When I cleaned them the first time it was... well not rushed, but it was more of an exploratory cleaning than a full on 'take everything apart and have it soak for hours' sort of deal. It did seem to improve things though apart from this. But I'm comfortable with taking them apart now so it's no big deal if I have to do it again.

Thanks again for the advice, everyone. I'll give it a go tomorrow!

[Senator_Kang]

Huzzah! Progress!

I checked the choke which seemed alright. It wasn't a totally smooth action but it definitely retracts all the way.

I did however notice the air bleed port thingy for the mixture screws just after the butterflies. They all appeared different, and then I remembered what I had read about them... well, all being different. So I zeroed them all using the fingernail method, screwed em out 2 turns, then bench synchronised the carbs as that all looked different too.

Fired it up and it idled nice and smooth. It seemed quieter, too, even before lowering the idle back to 1000 (it was about 1200-1500). A little unsteady but I expect that due to my unskilled hands.

I took it for a spin and got some heat into it, and yay! No more hanging at RPMs! Pull the clutch in and it drops down nice and quickly.

If anything it's a little *too* lean now I think, because it misses a little when you give it some, and up in the midrange under light or medium throttle (not game to give it the full throttle just yet, this is my first big bike  ). I expected it to be a bit lean I guess because the cans are big and loud off some other bike from a previous owner. When the pods arrive from RPM I'll get someone who knows what they're doing to give it a proper tune