Where is that FZR carb discussion please?

Started by pinholenz, January 29, 2017, 08:55:13 PM

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pinholenz

Can someone point me to the discussion about taking carbs off a 4 cylinder bike and using 2 of them to drive an XZ?
Mine is running fine at present but there is a local guy who is interested in looking at an alternative apart from the Weber IDF 40's. For the life of me I can't remember where the discussion unfolded and what the results were.

Thanks
Only one '82.5  eXtreme Zen 550

pinholenz

Found it! Its Walt_M's thread in the " '83 Mods" discussion on the General Board

This thread, along with the work on the Weber IDF40's, is such a game changer for future generations that it really ought to have its own thread in the Technical or Upgrades section. Could a moderator oblige by bringing that together so it is more public please?
Only one '82.5  eXtreme Zen 550

fret not

I have a couple thoughts regarding changing carbs, as I am in the geologic process myself.  The conversion to two carbs will take some fabricating skills.  Walt and Ron McCoy have mounted their carbs straight up from the original manifolds and fabricated the linkages between the carbs.  This might be the easier method but I'm still not sure yet.  I have taken the route to keep the two carbs together as the factory put them, and set aside the other two carbs.  This keeps the factory connections between the throttle shafts and choke mechanism.  To make the carbs connect to the cylinder heads I have fabricated some new manifolds from heavy steel tubing that is mandrel bent to about 45 degrees.  This requires making flanges to weld the curved tubing to, and fitting the ends of the tubing to both the flanges and to the carbs.  This sounds a bit redundant, until you try to do it.  It takes three hands and there is barely room for two.  Now to get the whole thing over to my brother's shop to be welded, some time.

In the final analysis I think it might have been better to make up a new manifold for a larger single carb.  The carbs from a Honda Super Blackbird (CBR1100xx) are down draft 42mm for one or two years, then they went to fuel injection.  One of those 42mm carbs would suffice for a 550cc engine, if one can be found for a decent price.

There is precious little space between the cylinders on a XZ550 for two carbs, but it can be done.  The trick is to make a neat and tidy job of it.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Walt_M.

Yes, it is my fault the carb conversion did not get it's own thread. I was planning several changes, electric fuel pump which is related and front brakes that were not. Maybe Ron can fix it. I will ask.
Whale oil beef hooked!

fret not

Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Rikugun

fret nut, One of my brothers made intakes similar to what you described for a snowmobile application. The tubes and flanges turned out well but the welding process warped the flanges a bit despite care to avoid this from happening. His intent was a simple gasket between the cylinder and flange but the warpage needed to be addressed before a good seal could be achieved. I also wondered if the gasket alone would be a sufficient thermal break between the engine and carb.

I'm not suggesting your idea won't work but just something to consider.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

fret not

Rik,  the process is not complete unless the surfaces are made good.  A skim with a milling machine or some hand work on a stone would be required to true the surfaces, then a gasket should complete the job.  If heat is a problem then insulating spacers can be made.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Rikugun

Quote from: fret nut on February 18, 2017, 12:24:22 AM
Rik,  the process is not complete unless the surfaces are made good.  A skim with a milling machine or some hand work on a stone would be required to true the surfaces, then a gasket should complete the job.  If heat is a problem then insulating spacers can be made.

Good deal. I should have known you had already considered these issues.  :)
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan