Author Topic: Did we decide how to fix the 82 Vision "stumble"?  (Read 5576 times)

RedBaron

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Did we decide how to fix the 82 Vision "stumble"?
« on: October 25, 2013, 11:25:13 PM »
Thanks. I did try and read all the posts on the subject but figured there was a final solution officially sanctioned by the Visionaries.
She is a slim and beautiful 82, so true, black and white and red all over!

dingleberry

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #1 on: October 25, 2013, 11:50:48 PM »
I'd like to say the YICS just for a laugh. What sort of hornet's nest have I stirred up..
You like, oui?

Jimustanguitar

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #2 on: October 26, 2013, 01:20:09 PM »
It's hard to make a blanket statement that describes exactly why because there are so many factors that come into play. There's not a single answer, but here's my list:

Working vacuum flap and clean air filter
No vacuum leaks (this includes rubber hoses, YICS system or capped off ports, vacuum flapper, intake boots, carb gaskets and o-rings, etc)
Clean carbs (moving floats, working needle valves, clean jets and passages, clean jets and passages, working fuel filter is advised, properly functioning petcock, clean jets and passages)
Properly set up carb (correct jets, correct float level, properly synchronized, adjusted for proper mixture, adjusted for idle, lather rinse and repeat several times)
Properly adjusted valve lash (credit goes to Riku, thanks for the reminder).
« Last Edit: October 26, 2013, 01:22:08 PM by Jimustanguitar »

Rick G

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #3 on: October 26, 2013, 07:38:27 PM »
I junked the YIKS after the 3rd rebuild , don't miss it  at all!
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Re-Vision

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #4 on: October 26, 2013, 09:01:48 PM »
My bike had the stumble when I bought it, Rick cleaned the carbs and I synched them with the YICS. No more stumble.     BDC

RedBaron

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #5 on: October 27, 2013, 12:53:26 AM »
I don't pretend to know very much on the subject. But I can share what I read in the first CYCLE WORLD review of the then new 82 Vision. I read that the new bike had this stumble "when cracking the throttle between 4000 and 5000" revs. It did not occur with an earlier tested bike located in Japan and occurred at 3000 revs in the CYCLE WORLD review bike after Yamaha took back the bike, tuned it and returned it for additional testing. So the stumble "moved" but was not eliminated after work by factory mechanics. This means common tuning efforts do not eliminate it but move it to a point where it might be more tolerable. 

Now for my opinion, worth nothing except to me at this point, I know.

This CYCLE WORLD test bike was a bike with no wear and so this means it is not due to gummed carbs or a poor electrical system or bad valve adjustment but in something mechanical in the new carb that needs change.

Since nobody reports black smoke from an over rich mixture and since air flows better than fuel it is likely a temporary fuel/air mixture toward the lean side, too little fuel.

Since the bog does not occur in all situations where the accelerator pump is required then it is not likely that, although increasing the accelerator pump action might mask the issue by lending more fuel to cover the temporary fuel shortage.

So, I suspect we are lacking fuel flow at 5k revolutions somewhere in the intermediate or high speed circuits, those passageways that allow more rapid increases in fuel flow at different RPMs. I am guessing the intermediate circuit since the issue does not occur at higher revs. They are too small or blocked from the factory with something. So it is a blockage in the fuel circuit(s).

I've read about the cast sand blockage theory in one of the circuits and while not knowing if it is true or not, there is some blockage that occurs in most 82's and that tell me it is a "manufactured in" blockage in these circuits.

I know that many times one cleans their carbs and the stumble is reduced or goes away. To me this also lends credence to the cause being partially closed circuits from the factory that get worse with use and then get better after cleaning, perhaps even to the point where the original passageway reduction or blockage is cleared or itself reduced to the point of not causing the lean mixture any more.

So, if anyone has overcome the Vision stumble by clearing or increasing one or both circuits then I would like to hear from them on how much they opened these passageways and with what approach.

Thanks to everyone for listening and adding to the conversation.

- Art.
« Last Edit: October 27, 2013, 12:59:47 AM by RedBaron »
She is a slim and beautiful 82, so true, black and white and red all over!

dpequip

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #6 on: October 27, 2013, 10:14:16 AM »
I've posted information previously on this forum that came from Yamaha "Back in the day" when I was setting these bikes up from new in the dealership and got a lot of disagreement.  I'll wade in one more time but all I can say is if it works for you use it! If it doesn't, than your on your own to find a solution.  I'll go with what has worked for me in the past as I am not one to re-invent the wheel. 

I had an extensive conversation with a 30+ year Yamaha employee this summer at the VJMC national convention.  This individual was directly involved with the "Fix" for Visions back in 1983 and was the author of several tech bulletins on the subject.  Short of the engineers in Japan this person probably knows more about the fuel system on these bikes than anyone else in the US.  He was also involved in roadracing a Vision back in 1983-1984 time frame.  That said, here were his comments:

YICS was a marketing thing and maybe had some emissions reduction effects.  As for performance his opinion was "It was a marketing thing"

The 1982 Vision fuel system was undeveloped and under engineered, released before it was ready. 

The best was to get a Vision to run right is to get a 1983 fuel system.  This includes petcock, Intake boots, carburetors,  and fuel pump.  We all know the 1983 carb setup is completely different animal and the reason is, it works much better.  Its also good for an additional 5HP 

The vacuum actuated flapper is a major improvement and required to get things close to being right.

That being said he said a 1982 fuel system can be tuned correctly to run under a very limited set of conditions.  It can be tuned for a particular temperature, elevation and riding style and run well.  He said you cannot tune for 90 deg at the beach, take a Vision 5000ft up in mountains at 65 deg and expect it to run crisply as you tuned it previously.  The fuel system just does not have that much leeway in it.

His recommendation to me was to find an 83' fuel system and put it on the bike.

I don't know if this answers your question but may shed a little more light on the subject
1982 Yamaha Vision Owned Since New.
Mods:Euro Primary Gear set, Euro footpegs & controls, Yamaha 1/4 Fairing, Braided Stainless lines, Forkbrace, Tapered roller bearings in steering, '83 rear Shock

Rikugun

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #7 on: October 27, 2013, 11:33:08 AM »
While in theory a great idea, the scarcity of '83 fuel systems makes it impractical for most to source. Then there is the issue with petcock repair parts availability...  :(

I think RedBaron may have been eluding to what dpequip has said about the '82 system being inherently defective - sorry - underdeveloped!  ;)  There are conditions that can either exacerbate or mask the symptoms but at the end of the day the thing will not be perfect. That's part of the allure of the bike but I wouldn't mind "stumbling" upon a permanent fix.  ;D  :D

...... This means common tuning efforts do not eliminate it but move it to a point where it might be more tolerable.  agreed and some are better than others

Since nobody reports black smoke from an over rich mixture and since air flows better than fuel it is likely a temporary fuel/air mixture toward the lean side, too little fuel. I often get complaints of rich exhaust from those behind me on group rides. Having said that I agree this is not the stumble culprit.

Since the bog does not occur in all situations where the accelerator pump is required then it is not likely that, although increasing the accelerator pump action might mask the issue by lending more fuel to cover the temporary fuel shortage. I tend to agree with this

So, I suspect we are lacking fuel flow at 5k revolutions somewhere in the intermediate or high speed circuits, those passageways that allow more rapid increases in fuel flow at different RPMs. I am guessing the intermediate circuit since the issue does not occur at higher revs. They are too small or blocked from the factory with something. So it is a blockage in the fuel circuit(s). I'd include pilot circuit in this theory

I've read about the cast sand blockage theory in one of the circuits and while not knowing if it is true or not, there is some blockage that occurs in most 82's and that tell me it is a "manufactured in" blockage in these circuits. I don't doubt someone found sand in their carb but doubt it is a universal V problem

I know that many times one cleans their carbs and the stumble is reduced or goes away. To me this also lends credence to the cause being partially closed circuits from the factory that get worse with use and then get better after cleaning, perhaps even to the point where the original passageway reduction or blockage is cleared or itself reduced to the point of not causing the lean mixture any more. sounds reasonable. It does act like fuel doesn't keep pace with air when the throttle is cracked open. The sudden pressure drop has it at a loss momentarily. A CV carb uses a vacuum slide to buffer this effect. It seems like the flapper was meant to do the same but is more of a Band-Aid than a cure.


It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Re-Vision

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #8 on: October 27, 2013, 04:52:05 PM »
Allude not elude. lol    BDC

Rick G

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #9 on: October 27, 2013, 05:39:53 PM »
I disagree with some of the opinions expressed by the  Yamaha employee. The 83 system was overly complicated and unnecessary. At this point parts are unavailable for most of it  and so is a bad choice . I usually won't work on '83 carbs as there are almost zero parts available for some of the critical  components.
A well set up '82 set of carbs  will perform very well under a variety of conditions. I ride from  500 feet elevation to 7000 feet , and have had reliable performance  up to 6500, above  that it will be spotty . But , them so will most carbereted bikes!

 When working at  Dunton motor sports on Arctic Cat ATVs  we had customers who wanted to use them at elevations  as high as 8000 feet , so we re jetted them. Then they would want to take them to 500 feet in the winter and complained about poor performance . No one seemed to under stand (and didn't want to under stand )  that the needed to be re jetted to that altitude . They are NOT a car , with 4-6 or 8 cylinders.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

RedBaron

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #10 on: October 27, 2013, 09:04:54 PM »
The CYCLE WORLD article said the problem did not happen on bikes tested in Japan so that might imply the issue is with U.S. product. Given that reach is true, perhaps European carbs work as they should and has anyone brought one over to use and found the stumble issue fully resolved?
She is a slim and beautiful 82, so true, black and white and red all over!

munkyfistfight

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #11 on: October 27, 2013, 10:00:08 PM »


I recieved these bad boys from a friend recently.... 8)
Those who play by the book will always be beaten by those who write their own. -Travis Pastrana

munkyfistfight

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #12 on: October 27, 2013, 10:07:19 PM »
I nixex the YICS this year and haven't had a problem and noticed no change in performance or fuel economy. I also added the MAC exhaust as well.
Those who play by the book will always be beaten by those who write their own. -Travis Pastrana

RedBaron

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #13 on: October 27, 2013, 11:15:46 PM »
Mine is actually the March 1982 Cycle magazine. I plan on not installing my YICS.
She is a slim and beautiful 82, so true, black and white and red all over!

Glyn

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #14 on: November 02, 2013, 06:06:21 AM »
I had my Vision for a few years and have in the past posted my thoughts of developing another carb for the Vision. I tried everything to remove the stumble on my bike and in desperation constructed my own manifold and fitted a Weber IDF downdraft carb. IMHO the venturi's on the Mikuni are too large and being cast cannot be changed. The Weber allows fine tuning of the Venturi size and I ended up with smaller  venturi's. It pulled very cleanly from a top gear roll on. I've now sold all my Vision parts after the bike just stopped one day at the gas station. I think it was the CDI but by then I was looking for another project and sold it to a chap who is going to race it. I now have a Yamaha XV500 (the air cooled smaller brother). It goes very well. Not as smooth as the Vision but no stumbles. It has two CV downdraft carbs which are easy to work on. I think they could be made to work on the Vision if the space would allow. My Weber fitted really well since was of a very similar design and size to the Mikuni. The visions are great fun and so smooth for a twin. I may get another one day.   

pinholenz

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #15 on: November 02, 2013, 06:51:06 AM »
Hiya Glyn,
You may see me rolling by at the end of your road as I head up through Oratia on the West Coast Road. Flag me down if you do.

My stumble is at throttle opening in all gears. Drives me nuts when the 250's accelerate smoothly at the lights but I gag, fall behind spluttering and then she roars into life. Or I have to  slowly roll on the throttle like a sedate old man without a care in the world and going nowhere fast.  Either way the Vespas and the  250's leave me for dust.

I am part way through a  550 full carb rebuild to see if it makes a difference. I also have a spare  set of XZ400 carbs. Did XZ400's stumble?
Only one '82.5  eXtreme Zen 550

Prophet Of Doom

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #16 on: November 02, 2013, 09:35:55 AM »
Hi Glyn, long time no see.
I managed to prise your old Weber out of Iain's clutches, and the plan is to have it up and running in my bike soon. 
I love the look of the giant K&N air filter sticking up out of the Weber - it's a shame it gets a tank over it.

Last time we heard from Treedragon he was running a Weber now as well, though  different model.

pinholenz

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #17 on: November 03, 2013, 11:25:17 PM »
Hiy a Glyn,

When we last spoke, you mentioned that you may have some drawings of your manifold design. Did you find them?

I am thinking that with the advances in 3D printing, some enterprising soul might be able to create a 3D file and do a rapid prototype of your design. It would be a great starting point and maybe POD could post some pics?

Only one '82.5  eXtreme Zen 550

Prophet Of Doom

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #18 on: November 04, 2013, 06:12:31 AM »
I could be persuaded to take some pics.  Give me a reminder if I don't post them within a week.

couchflyer

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Re: Did we decide how to fix the 82 Vision "stumble"?
« Reply #19 on: November 04, 2013, 10:07:50 AM »
The YICS system is an enigma.  On my black 82, it runs great/better without the YICS and the red 82 seems to like running with the YICS.
1982 Yamaha Vision ~ 1 Black & 1 Red
2008 Ducati Hypermotard S
2008 Ducati 1098 ~ Track only
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