Best water cooled, mono-shocked, Japanese sport 550 V Twin ever made.

Thanks, Glen and Russell, for reminding me -   :-)

https://scontent-a-pao.xx.fbcdn.net/hphotos-frc1/t1/1970707_10152257752322258_826998935_n.jpg

Mike "Fug" Johnson  about 1982


Russell Johnson AFM 750 Twins Champion  1984
exiting Turn 11, Sears Point

 


Christianson, Glen (H USA) wrote:
Marc, Are you laughing at me yet? I just bought a 1983 Vision. In searches, your name came up as having raced one, now I am laughing. Not at you, but at the effort you must have made to make the Vision work at speed. I have not picked the bike up yet but will Saturday 10/24. Care to call me and fill me in on what I am in for? This will be a street rider, no attempt at racing it is planned. Just want it to work well. Glen.
 
Glen Christianson

.................................

Ya know what they say - you can be "good as gold for all of your life, but ride just ONE Vision and you  are "Vision Rider" for the rest of your life".<biggrin>

The Vision was Yamaha's early foray into high rpm / V Twin engines. It had a pretty darn strong engine.

I raced an 82 XZ550 and an 81 XJ550 Seca in the AFM in  81 and 82. I think maybe I got a 3rd as best finish with each. In the USA, both bikes had a single front disc and that would simply overheat during a race, no matter what pads I used. I was unofficially, corporately "tasked" to take both bikes on the California Hwy 1 Sunday Morning Ride and make them "look good" over the Kaw gpz550's.
I think that we did pretty well on the Vision and the Seca was simply awesome.

Regarding the Seca, to this very day, I haven't ridden a bike that was so balanced. Think like being able to push the front end (to help slow the bike) with the rear end slightly stepped out entering the corner and still understeer (or not) the front end while drifting the rear wheel on the exit....... 2 wheel drifts were natural.

 Conversely, the Vision had a 45/55 weight bias and you had to run a pretty large, sticky front tire just to avoid washing out the front end.

The engine of the Vision was better than the Seca, so the magic combo would have been the Vision engine in a Seca similar chassis with dual disc brakes.

The Vision had better power coming off corners and about the same topend as the Seca. The Vision, being a driveshaft bike, was limited on the track -  But the gpz550 guys hated hearing that 10k v-twin drone coming around them coming off the corners.

I raced one in the AFM, sponsored by Karl's Motors, Richmond, CA and with a little help from my Yamaha Motor friends. Mike Johnson, from neighboring Berkeley Yamaha was a  "fast guy" who rode a Vision, too. I think he won the 750 Twins class and I got second as I had to finish 2nd in the last race, had lost my "Vision" ride (casualty of the 81/82 recession - another story) and had to ride the only "under 750 twin" I could borrow - Frank Mazur's cb400 Hawk. No time to set up the suspension (he was about 135 lbs and I was about 170 - so I raced it like that, Uncle Paul Bostrom and Mike beat me and I compressed a vertebrae in my neck after bottoming out the suspension in that little Turn 1 depression at "the spring". (another story).

Back to the Vision -

We both kept working on the first year Visions' notchy "on and off" throttle bogging. It made the bike annoying to drive around town and funky at high rpm's, teeny throttle.

For fun, every week, both of us would jovially call Yamaha Tech Dept and say "Hey! What's up with Vision carbs?" to the same guy every week, who was tasked with, I guess, answering the Tech Line and fixing Vision carbs.

One day, after months of changing every jet in the carb, I found a book on Weber downdraft carbs. The Mikuni - Solex downdraft carbs that the Vision used were almost identical to a Weber downdraft.

I traced the fuel paths and verified that the suspected fuel bottleneck was in the off idle bleed holes at the butterfly or the butterfly "angle" was wrong. Since I couldn't change the butterfly.... I decided to enlarge the 4-5 bleed holes to allow more fuel. (no, Ivan, you weren't the first guy to do that.... :-)`

After struggling with un assembling the rack of carbs, pulling out pressed in caps, I took a small number drill and pin vice and slid it into the first hole.
Instead of dropping right in, it sort of "oozed in".
I pulled out the bit - The flutes were filled with a claylike red residue - Think "Shop class"..... fine casting sand..... or rust(ish).

I went to work breaking up the residue and finally got them clean.  Reassembled, tested, FIXED!  :-)

It wasn't Yamaha's fault, they don't make the carbs. But it was their problem........

So....... Monday rolls around and I can't wait to make our weekly call to Yamaha Tech Support.
 

Ring.... ring.....

Yamaha Service...

Hey, what's up with Vision Carbs?

Well, our engineers are working on it in Japan and we don't know, yet.

I fixed it.

What?

I fixed it. There's casting sand plugging the off-idle bleed holes. I cleaned the holes and the carbs work fine.

Really?

Yep.

Ok - we have some warranty carbs in the back, I'll check - Thanks -

Ok - Bye -

A week later, I had another tech question and just for fun, I started the call with "Hey, what's up with Vision carbs?".

"Well, our engineers in Japan have identified the problem as casting sand in the off-idle bleed holes."

Ouch! LOL!

"DUDE! I'm the one who told you that last week! Remember? Engineers in Japan, my a**!

Of course he apologized and was embarrassed - but it was pretty funny to listen to early "corporate" speak. I mean like, how could some kid who works in a "bike shop" in the nether regions of NORTHERN California ever figure anything out? Why, we here, we have "engineers"! (Someday I'll write out how the Yamaha 1981 XS650 twin's "chattering clutch" got fixed after months of replacing new part number clutch plates with little difference..... It rolls right into "How to fix chattering yzf750 and 1000 clutches")

Aside from that -

Clean out off idle bleed holes if the bike is "notchy" just off idle - They had casting sand or something in them.
Like just about every other early 80's bike, the rear shock was dreadful when overheated (and on the Vision at Sears Point that was about 2 laps on a hot day). I even tried wrapping a plastic bag of ice in a towel to help cool it... :-)

Cut about 1.5 inches off soft end of front fork springs. Respace to get proper ride height.
Choose oil to suit. Maybe 15wt.
Use oil height to control front end dive. Higher than stock.

Weight distribution is 45fr/55rr. Needs big soft  front tire or it will wash the front end out on brakes entering a tight corner so fast your head will spin....... 3.60 K81 was way too small.
I still remember first practicing and going into 11 at Sears. Brake, hard, shift body, pull bike right. Ahem.... why is it dark? Why is there asphalt whizzing by my face shield? Why am I face down down the track? Where's my bike? Who hit me? Why am I here? Where am I going? Will I ever stop? Will Lassie find Timmie in the well?

Needs a fork brace if the laterally flexy forks bother you and slows you down in r-l and l-r quick transitions. (like turns 8/8a at Sears).
On any bike, did you know that if you are, for example, 90 mph, wheels drifting, leaned to the max left, crawl over the right side of the bike and "yank"  the bike hard for the quickest possible l-r transition, that the bike pivots around about the center of gravity and the front wheel actually levers off the ground 1.0-2.5 inches? I always wondered why, during the transition, the front end felt "so detached". Till I LOOKED! I stopped trying to transition faster than 1-2 inches of "bounce and float".........

The Vision had much better midrange as compared  to the current inline fours and I still think that it sounded cool. If you can record a dyno run and email it to me, that would be cool!

I only did "supersport" type mods - If my memory hasn't failed me, there other guys who built chain drive conversions, big bore kits, cams, etc........

Marc


LINKS

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Wikipedia Yamaha_XZ_550 Vision

 

 

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