High Idle - only when up to operating temp though

[Protonus]

This is the only drive-ability issue I have left with my Vision.  It otherwise runs perfect at all RPM's, has no hesitation, beautiful throttle response and power.  Unfortunately, this issue remains, and they failed my inspection for it  >:(
When the bike is cold, it starts up and idles beautiful.  Tiny bit of throttle, little bit of choke, BAM, works every time.  It idles beautiful around 1200 ish and I can adjust it to whatever I want with the screw.  Sounds great.  Runs great.  Idles perfect IMHO.   

Once the engine is up to operating temp though, it has a high idle. If I let out the clutch a bit so the RPM drops back down to 1200, then let go of the clutch, the idle will creep back up to between 2500 and 3200 RPM's every time, within just a few seconds, every single time.  Really annoying at red lights.  It always does this, every time I drop the speed down in gear and clutch in or sit in neutral it creeps back up.  Once the engine is cold again though, it's fine.

I figure it's a vacuum leak, but not sure why or where.  I've replaced all the vac lines, rebuilt the petcoke, sealed my YICS box.   I made sure all the vac lines are routed properly, by using my spare parts bike for reference, and both the Yamaha and Haynes manual.  So far with carb cleaner and starting fluid "testing" I can't find a leak.  I'm going to try sealing my carb boots with liquid electrical tape as suggested elsewhere.  I'm going to go thru again and try looking for leaks, but I'm hoping someone has a suggestion before I pull my hair out. 

AFAIK the carbs have been recently fully dipped, all jets cleaned, and the carbs sync'd, by the PO I bought the bike from who is a very skilled mechanic and is very familiar with carbs.  He is on vacation overseas though for another month.  I have a full spare parts bike I can rape for parts if I need to swap something, but I suspect the carbs/fuel system in that bike are terrible clogged up  with old jelly gas, as it sad for at least 5 years without running.

One last thing - the bike also idles even higher, if It's on the kickstand, and the handle bars are turned left like usual when parked. If I straighten the handle bars, the idle drops down either to normal, or the "lower" high idle it ussualy has.  As soon as I turn the handlebars left with it on the kickstand, it idles REALLY high when hot.  I thought maybe the float levels in the carbs get messed up when the bike is leaning like this?  But it still leans on the kick stand with the forks straight, and just turning them straight makes it better.  Is there something vacuum or fuel related that turning the forks would affect?

[Lucky]

for the high idle at left turn. check your throttle cable routing. it's off.

for the creep up hi idle, clamp off or cap the YICS hoses. i know you said you sealed the YICS, but you may have missed a spot & that sounds likely since it creeps back up slowly.  do the water test.

also you know 2 of the YICS screws have gaskets under the head right?

--Lucky

[QBS]

Any change in idle that can be initiated by just turning the handle bars screams misrouted throttle cable.  Your idle change when not may be related.  Would really look very closely at your cable routing.  Observe (or feel) the throttle linkage for movement while the handle bars are being moved lock to lock.

[jasonm.]

I think it's the cable...throttle routing. ALWAYS check the easiest thing 1st. TAke the fuel tank off. Next get a manual. If no manual, then the throttle cable is to run inside the right fork tube by the headlight on an '82 . Then makes a straight run for the carbs above the lower triple tree, yet  below the main frame tube. It should be no where near touching the fuel tank. Also look at the vacuum hoses that it runs near...as one could be causing the incorrect routing. How much slack do you have in the throttle  cable???? seems like none from here.

[Protonus]

for the high idle at left turn. check your throttle cable routing. it's off.
for the creep up hi idle, clamp off or cap the YICS hoses. i know you said you sealed the YICS, but you may have missed a spot & that sounds likely since it creeps back up slowly.  do the water test.
also you know 2 of the YICS screws have gaskets under the head right?
--Lucky

You nailed it as far as the high idle on left turn, it's definitely the throttle cable. I watched it as I moved them and it pulls it tighter/bends it and makes the idle go up.  AS the fork turns it's kind of bending the cable.  I have a 82, but it's a late model that I'm assuming was dealer converted to have the full 83 fairings.  Not sure yet how it's misrouted yet as it "looks" ok and looks like what is described, yet it's happening.  It is inside the right fork tube, and it sort of rests on the lower triple tree. I wouldn't be surprised to find a major issue in how it's routed though, there was a LOT of stuff misrouted on this bike, I think the PO got it with the engine and shit out off the bike originally and he did his best guess to get everything routed right. But I found many vacuum lines criss crossed or plugged into the wrong ports etc.  I have the spare parts bike though, so I can reference that to figure how it's wrong, or at least swap the cable over.

However, that isn't my high idle when hot problem though.  I've pushed against the throttle and made sure it's closed before.  I will try capping off the YICS.  I am aware of the gaskets under the two YICS screws.  I epoxied the screws in place during the fix.  I've water tested it and detect no leaks externally.  There is a very slight internal leak between halves.  I am going to have a friend make a aluminum replacement for the YICS chamber.  He has access to plate benders, CNC, and a TIG welder, and this should be cake for his fabricating skills.  If it comes out nice he may be interested in selling them, we'll see. 

[Lucky]

There is a very slight internal leak between halves.

I'll bet that's it...

[Tiger]

 :)

One last thing - the bike also idles even higher, if It's on the kickstand, and the handle bars are turned left like usual when parked.

On the throttle cable, just below the twist grip...there is a knurled round plastic lock 'nut' (disc). Back it off slightly and slowly twist the other part (up or down, I don't remember off hand) until your idle settles back to were you set it up at...Try this first, before you start rerouting what may be an o.k. throttle cable ;)

Let us know buddy.......

                   8) ....... TIGER ....... 8)

[George R. Young]

Suggest you try tweaking the mixture screws 1/4 turn richer.

[Protonus]

There is a very slight internal leak between halves.

I'll bet that's it...

LoL, you nailed it again... I capped off both YICS ports and the problem immediately went away.  Entirely.  I have a perfect idle now at any temp, in fact I had to turn my idle speed way up because it dropped quite a bit even when cold.  It's ridiculous that such a tiny leak between halves causes this huge of an issue.  It must be because it's not just a vacuum leak but that it's getting extra fuel too, when it's an internal leak. It's amazing to me that  Yamaha knew how this system worked and didn't go with two entirely separate chambers or a double inner wall, or heck, something more robust then plastic!  This explains why the problem seemed to get a lil worse when I switched to  my spare YICS chamber that I glued up - it has a little bit more of a leak between halves then my stock one did.  It also explains why the problem got a lot worse when I fixed the YICS vaccuum lines routing and replaced them with new ones.   Guess I'll have to get on one of my buddies to fab up an aluminum replacement sooner than later.

Without the YICS, I'm definitely noticing a difference though, and I will be putting it back on once I either fix one or get a replacement.  I'm with the camp that thinks that the YICS is more then an emissions or MPG device, that Yamaha wouldn't have spent all the money to put it on the bikes and promote it heavily in marketing material if it did nothing, etc.  Without the YICS, I am getting stumble and hesitation on throttle tip in where as I had none before.  It's bad enough it sometimes dies off idle when engaging heavy throttle, I had to raise my idle speed up a bit to help reduce that.  I also seem to have less top end power, it doesn't seem to pull as hard from 7k+ rpm anymore, seems to have a few less ponies.  Also, the tone of the engine changed a bit, especially under heavy load like low RPM high throttle.  This all maybe because it was running leaner with the YICS on due to the leak, or maybe my carbs need resync'd without it?   But either way right now it doesn't run quite as nice overall without it, with the exception of it idling perfect.  Very curious how it runs when I have one that doesn't leak at all on there.

Has anyone seen if you can unscrew the YICS ports/hose barbs, on the head?  Are they screwed into an NPT boss or something standard?  I'd really like to replace them with an NPT to AN line ideally, so I could put AN ports on my new YICS replacement, and ditch the silly hoses for stainless braided AN line, which should highly reduce collapsing etc. 

[Extent]

The YICS makes a demonstrable increase in horsepower (even if only small) across most of the powerband on a dyno, and a fair increase of torque right around 4k.  IMO there can't really be any question as to it's effectiveness, but many don't think it's worth all the hassle :p

[The Prophet of Doom]

I am going to have a friend make a aluminum replacement for the YICS chamber.  He has access to plate benders, CNC, and a TIG welder, and this should be cake for his fabricating skills.  If it comes out nice he may be interested in selling them, we'll see. 

Dibs on one of your buddies aluminium YICS boxes
Trouble with epoxies is that they test fine, but blow out in a pretty short time.  Gasket and RTV as on lucky's site seems to work a lot better, but I still have doubts about its longevity.

[Rikugun]

Extent, do you have a link to that dyno info or a file to share? I've heard the YICS debate since joining but have yet to see hard data to support the claims.  Seat of the pants performance claims do little for me so I'd love to see some empirical evidence.

[Extent]

[Protonus]

Extent: thanks for sharing! Nice graphs, hadn't seen a dyno for these engines yet.  Is that an '82 with the '82 carbs do you know (the '83 carbs made more power right)?  Do we have any more info on this dyno or what thread this came from? Is that an engine dyno or was this on the bike at the rear wheel? 

Wow that YICS gain while noticeable is tiny on the graph.  My seat of the pants dyno says it's more then like a 2hp loss at the top end, feels more like 8hp at 7k.  i'd like to see this done again.  I do have a bike dyno available near, perhaps once I get my YICS sorted out I can try this too. 

What's most surprising is how much worse it is with no air filter!  I wonder if that was no air filter BOX or if it was just the filter it self? 

[jasonm.]

for hose use quality fuel hose 1/4" or 5/16".You know double rubber with the braid in the middle................it will not collapse

[Rikugun]

Thanks for the chart Extent. Based on that one sample the results confirm what my seat of the pants dyno told me: The YICS doesn't make a significant difference. Certainly not enough to warrant repairing mine and wondering when it will crap out again.  :)

[kev10104]

My daughter's boyfriend had similar issues with his rpm's going up to 9000 at 100 klms.I jumped on his bike and immediately noticed the clutch was tight and not disengaging so I adjusted it and it runs beautiful.That might be an issue with you as well.