Z1 plunger replacement

sf4t7 wrote:

Tried Clay's oring method to seal the choke plungers, it worked perfectly. And even better, it's cheap! Just make sure to use viton orings and you'll probably never have to do them again.

I agree with the viton O-ring suggestion.  Buna-N/Nitrile O-rings swell in gasoline and are great for carbs when the O-ring is captured in a space.  When they swell, the seal gets tighter, which is perfect.  When it sits on a choke plunger, O-ring swelling isn't ideal; Viton would be better for that application—my opinion, of course. 

But.you might "test" the superglue ability to stick to the Viton, sometimes it doesn't.. Been there, done that.

Hmm! Never thought to check that!
Choke is still working fine so I don't want to mess with it, haha. Next time the carbs are off I'll be sure to check them, though.
I did make sure the surfaces were  clean and dry. (And waited for the superglue to cure before assembling plungers in carbs.)

  We've been experimenting off & on with replacing the entire seal in plungers with round CS Viton O-rings.  Soaking the OEM seals in acetone for a few days causes them to swell & become quite soft.  It's then fairly easy to very carefully use a jewelers flat blade screwdriver as a chisel to cut them into small pieces & gently pick them out of the plunger's seal cavity, leaving the retention roll unchanged and the center needle true on it's axis.

   We don't really see the need for the seal to be flat where it meets the seat in the carb body.  Spring pressure alone seems to be sufficient to create a good seal using Viton O-rings of 70 durometer.  We'll wait for a Ridin' season before passing judgment.

Good Ridin'
slmjim & Z1BEBE

hardrockminer post=927208 userid=49877I swear by Keyster kits but not their plungers.  The ones I've bought don't have the pointy thing on the bottom so they don't seal as well as Mikuni.

   We've never fully understood the function of needle.  Plungers for most other carbs don't have them.  Best guess is coarse metering needle, similar in function to a main jet needle.  Seems that centering of the the plunger would be done by the bore  itself.  They're also soft & delicate.  If the needle becomes bent off-axis in the least it will bind in the hole.

Good Ridin'
slmjim & Z1BEBE

The needle allows a more controlled metering of the fuel.
Without it ( as with most Keyster copies ) the choke has a crude all on or off action rather than one that can the feathered like the original.
I've had many customers have me repair their original plungers after buying the Keyster Tornade kits which include the needleless items and found they don't function correctly. 
You will find that it is invariably 4 stroke carbs have the needle and 2 strokes don't although there are exceptions with both.

That's interesting Jim you've ran across a "bent" plunger tip? I've bags of these and coming directly out of any carb have never seen one bent. That's a handler issue, they are pretty stout. Reiterate what Zed Said, older two strokes rarely had them in TK/Mikuni variations. But those birds liked a rich mixture to fire, or/often without electric fast spinning advantage of engine to siphon from bowl. Quick Delivery before you wore your kicker leg out. The protruding needle stifles this to an acceptable level. And surely a side benefit of breaking-up raw fuel droplets/atomization. But.. the plunger serves TWO functions, fuel AND air cut. That's why lifting plunger fat barrel part, you can treat it like a throttle, adjusting RPM. It's just a controlled air leak thru engine side port routed to other side of slide/air cleaner. 

Here's a blast from the past Zed, remember these? Have had a couple friends bring me these Big ball/small ball replacement float seats. Sporadic sealing at best, sometimes/maybe/never ha. Came out in the 1980s and offered for cars and bikes. Actually pulled a set out of a Lancia carb set before replacing immediately. Noble concept but real world failure was imminent      

asphalt900 wrote:

Here's a blast from the past Zed, remember these? Have had a couple friends bring me these Big ball/small ball replacement float seats. Sporadic sealing at best, sometimes/maybe/never ha. Came out in the 1980s and offered for cars and bikes. Actually pulled a set out of a Lancia carb set before replacing immediately. Noble concept but real world failure was imminent 

    

Remember them ! 
I see them fairly regular especially in the vintage S&S Super B carbs that come attached to some Rajay turbos.
The ball is usually plastic in those. 
I also get plenty of plungers in with bent needles and have become quite adept at tweaking them straight without a thought as part of the refurb process and now have a couple of dedicated tools for the job.

That's Wild then Zed, bent plunger tips! I've amassed a bucket of probably 100 plus of those and have never witnessed a distorted version? Has to be arrogant ham-fisted behavior after removal.  

Most of them come through the post from all parts of the world and many aren't wrapped as well as i recommend.
Sometimes i'm amazed that they are still in the package i receive.
On a few occasions they have just been thrown loose in a stamped envelope and dropped in the nearest post box and once i did get an empty envelope with a hole in the corner..
The real fun begins when some arrive with no clue to who has sent them and i have to become Sherlock Holmes to figure out who's they are which often takes longer than actually doing the job.