Flapper door

[macroars]

I have gone through several carb adjustments and readjustments lately. Removed the carbs, removed the jets and blew through the holes with compressed air, readjusted, synced. Nothing helped. She kept on stumbling from 2000 to 5000.

Finally i found the problem. The flapper door had came off, and was to be found in the area behind the battery.

Now it is back on, and she is purrrrfect!

The carb attention was definitely not in vain after all...

[h2olawyer]

Sounds like you found the problem.  Great news.   ;D

That flapper door helps to decrease the volume of air and increase the velocity of the airflow.  It is - as you found out - an important part to cure the stumbles in the low to mid RPMs.  It is also why it is so difficult to get aftermarket air cleaners, like K&N pods, to work properly.  Normally, removing restrictions in the airflow at either intake or exhaust improves performance.  That's not the case with the XZ550.

Is your flapper door vacuum controlled?

H₂O

[macroars]

Vacuum controlled yes and no. What I understand is that it is the vacuum in the air box that opens the door. But it is not connected to the vacuum system of the engine. But now everything works great. Better than ever actually.

But when I was adjusting and readjusting the carbs, I could not stop wondering about why I had not read anything about replacing the cards with non-stock. Is it as rare as I belives?

[h2olawyer]

In the US, there was a carb upgrade for the 82s.  It consisted of a new top for the front carb, 135 air jets, a small disc air filter, a new airbox top and a new vacuum port to operate the flapper door, using engine vacuum.  For the old style door, some people have had great success epoxying a couple coins to the flapper door.  In the US, a couple nickels are customarily used.

There has been some experimentation by our friends in NZ, adapting a Weber to the bike.  I believe Glyn is trying the swap.  However, without an exhaust analyzer, it would be difficult to get things set right.  Another option is a Megasquirt fuel injection system.  I think there's someone looking into that option as well.  Otherwise, there are really no other viable options as yet.  With these downdraft automotive style carbs, it is difficult to adapt other carbs to fit.

H₂O

[macroars]

It might be the coin-effect I have obtained then. For the only reasonable thing I found to make the new hinge from, was some rather rigid rubber. I was looking at it when mounted, and concluded that it was a little less "floppy" than the original.

[Rick G]

Some people want to junk the vision carbs , but when there clean and  set up properly there excellent . Believe me, it would be much more trouble to adapt something else  to the vison , than to just get the stock one set up correctly.

[Glyn]

Just reading the posts and saw a mention of my Weber conversion.

Yes it has taken a little while to get everything sorted. I fitted a gas analyser for a while, it helped but you really just have to keep swopping those jets out and riding it to get it right. With Webers there is a mine of information on the net, so you can get it fairly close very quickly.

I really didn't want to go to the bother of changing out the carb but spent so much time swopping over carbs, cleaning etc I could never get it right. Mind you mine is an 82 however  with the poorer set up - I believe.

It almost looks like Yamaha copied the IDF Weber, it is that similar a carb. That's why I chose it. It was a common fitment to VW air cooled motors in the day. There is also a firm making IDF conversions for Goldwings and they've been on plenty of Harleys. It is a true downdraft carb so is ideal for our bikes.

It has the advantage (in my opinion and I'm no engineer), of better alloy quality, easy to change jets (done with the carb on bike), use of less restrictive filter and fixed a fixed throttle bar. ie the carb never goes out of synch. Once it is fitted that is it. Less (no) messing/cleaning and more riding.

My current set up is;
IDF 40 Weber Carb
F3 emulsion tubes
135 main jets
180 air jets
60 idle jets
32mm venturis
K&N mesh filter.

The biggest problem is making a manifold. I originally made one from steel that bolted onto the motor.
It looked terrible but worked. I've now made one in alloy out of an old Austin Mini manifold.
Any decent CAD shop could make a design up much better and then it would almost be a straight bolt on fix. I ride my bike in most weathers and in heavy traffic and am getting 47mpg average with no stutters or problems. Ill try to load a picture on my next post but for some reason I cannot do it at the moment. I've got plenty of pics and advice if anyone wants a go at this conversion.

I'm on pickteam@xnet.co.nz

My Kiwi 5c.

[Brian Moffet]

Ill try to load a picture on my next post but for some reason I cannot do it at the moment. I've got plenty of pics and advice if anyone wants a go at this conversion.

Glynn,

if you need photo space for this, let me know.  I've got some spare space.

Brian

[QBS]

Great report.  Thanks for the update Glyn.

[Brian Moffet]

Here's Glynn's carb setup.  Click on the photo for a larger image.

[Rick G]

great workmanship Glyn. I love the crest on the box below the carb.

[Glyn]

That's my late fathers regiment crest (Durham Light Infantry). The stainless steel box is actually just a cover I made over my mild steel YICS box. All the tubing etc exits at the base so it is hard to spot.

Had someone weld up all the aluminium which was a major job with all the alloy tubes/plates etc I manufactured on my trusty 1950's Southbend lathe. It would have been so easy to cast one if only I knew how!

[Tiger]

That's my late fathers regiment crest (Durham Light Infantry).

...and a fine, proud Regiment the D.L.I...Look up the regimental honer role 8)  Do not loose that badge my friend.

                  8).......TIGER....... 8)
ps Were is your father from ???

[Rick G]

My Step Father was in the Stormount, Dundas and Glengarry Highlanders (drawn from three counties east of Toronto) I still have his Glengarry . The cap badge was stolen during a reserve meeting in 1953.
During a visit to a gun show at the Los Angeles County fair grounds, I found a dealer in Commonwealth  military insignia and he had a large box full of cap badges. I dug for 20 minuets, not really knowing what I was looking for . I found a badge with three thistles , the initials "SDG" and a Gaelic script. I bought it on the off chance that it was correct . When I returned home , I dug out a picture ,taken in 1941 , of my Dad with the Glengarry on and was pleased to discover the badge was the correct one.
Even though he had passed on 14 years before I had the satisfaction of restoring his Glengarry
Sorry for high jacking the post , but life happens! :D :D :D :D :D :D

[Glyn]

Unfortunately it is not my fathers original, also from a dealer. My father came from a coal mining village in County Durham called Spennymoor. He passed away when I was 8 but still have fond memories of him ( he had MS). I'm doing a bit of an army retro bike (a CX 500), which I've also modified with Mikuni round slides
(no one has done that I can find), and an adapted CB 650 oil cooler kit. Is all green with all badges etc removed. The DLI became KOYLI (Kings Own Yorkshire Light Infantry) when my Dad was in the army. The bike has a personalised plate "KOYLI".

Although very different in concept it's amazing how similar the CX and XZ are to ride. The CX was actually highly tuned for a pushrod 500. Like the XZ they are unique with their own issues. Again all fixable with a little
TLC.

[Tiger]

My father came from a coal mining village in County Durham called Spennymoor.

:) Know it and been there mate... 8) If you look on a map, go north from Spennymoor and find Newcastle...head east to the coast and go north to a town called Blyth...my home town until I was in my early twenties!!! It to was a coal mining town...in the Northumberland coalfield.

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

[Glyn]

Most of those villages were Tiger.

I left, never to go back - except to see relatives.

Still fond memories but it's changed radically I believe.

Wonder if there are any Viisionaries up there?

[inanecathode]

Unfortunately it is not my fathers original, also from a dealer. My father came from a coal mining village in County Durham called Spennymoor. He passed away when I was 8 but still have fond memories of him ( he had MS). I'm doing a bit of an army retro bike (a CX 500), which I've also modified with Mikuni round slides
(no one has done that I can find), and an adapted CB 650 oil cooler kit. Is all green with all badges etc removed. The DLI became KOYLI (Kings Own Yorkshire Light Infantry) when my Dad was in the army. The bike has a personalised plate "KOYLI".

Although very different in concept it's amazing how similar the CX and XZ are to ride. The CX was actually highly tuned for a pushrod 500. Like the XZ they are unique with their own issues. Again all fixable with a little
TLC.

I noticed this too how similar they are. I like the smoothness of the cx though over the xz. The xz is a bit more squirrelly if you ask me..

[don_vanecek]

I test rode a CX500 in the early 80's as they were heavily discounted. Didn't get the impression the thing was hardly any faster then the CB350 twin I had, passed it up (and of course later got the Vision).

However Honda sold alot more of em then Yamaha did of the Vision, I know of at least two running CX500's in my area.  Had to chuckle as I went over and had a long talk with a guy I saw at the court house this spring, he was the original owner of his CX and bought his left over CX the same time I bought my left over XZ (summer 1984).

[macroars]

This feels like hijacking a thread, since I am returning to the originating topic.

With the present flapper door, my V is accelerating from 3000 to 6000 without any stumble, and she does consume less gas now. But she does not respond as good as she used to from 6000 to 7500. Do you guys believe that this is due to a too heavy opening flapper door to open, or can it be something about how the carbs are adjusted???