Choke plunger Vm28ss

Maxbou92 wrote:

 

Hello guys, does these Choke plunger fit on the vm28ss carbs?  There were Niche plunger, the seller tell me that ; eBay item number: 162890295846 Genuine Mikuni VM29 VM33 Smoothbore Starter Plunger Valve VM24/510

 

That drawing used to be on the Niche website but has been removed fairly recently.  We've never bought from Niche via fleaBay.  We've always bought direct from the Niche site.
www.nichecycle.com/mikuni/parts-by-categ...unger-by-mikuni.html

We used info from that drawing (same as above) to confirm, within the accuracy of a quality digital caliper, that they are the same dimensions as the OEM Z1 plungers.  Only discernible difference we see is, the shafts are raw brass as opposed to the grey (plated?) OEM plungers of 50 yrs. ago.

After testing a set of four in an a rack of early Z1-A carbs (17mm drain plugs), we bought a set of 24 of those plungers from Niche to update all our Z1's .  The plungers depicted in the drawing from Niche do fit & work perfectly in the VM28SS Mikuni Z1 (including ribless), early Z1-A (17mm drain) and late Z1-A carbs (w/ drain screws) we've installed them in.

We've not installed them yet in our Z1-B carbs, but we have no reason to believe they won't work, as they're essentially identical to the late Z1-A carbs in that respect.  We'll be installing the Niche plungers in our Z1-B's this winter during prep for Ridin' in 2025, for their 50th birthdays.

The ~50 yr. old seals in our OEM Z1 plungers we've taken out of service so far were compressed a little where they contact the seat, but no radial cracks were observed under high magnification in any of them.  We're keeping the old sets of OEM plungers on the shelf just 'cause.

We've never researched the seal material on those from Niche.  We'd have to defer to ZED1015 on that.

We've begun to use the choke lever to raise the plungers off the seats a little when parking the bikes, to help avoid seal compression from long-term pressure on the plunger seals from the springs.

All that being said, we've run the plungers from Niche for a few years now on four of our Z1's with no problems.  Too, we're of an age that if the seal material degrades in say, 10 ~ 20 yrs., we're very unlikely to care any more.

Good Ridin'
slmjim & Z1BEBE

Thank you very much, I will check those one on the website .. Ive found some plunger on Jetsrus.com, but When I proceed to payment, the website is bugging!! I have 3 of 4 spark plug that were black!! 

Maxbou92 wrote:

Thank you very much, I will check those one on the website .. Ive found some plunger on Jetsrus.com, but When I proceed to payment, the website is bugging!! I have 3 of 4 spark plug that were black!! 
 

Float level checked?

Good Ridin'
slmjim & Z1BEBE

New float, float needle, seat. Set all 4 at 26mm

Checked with the clear tube test next?

I would like to, but it’s not a drain plug like Zed says.. it takes a hose and adapter to use this method 

Maxbou92 wrote:

I would like to, but it’s not a drain plug like Zed says.. it takes a hose and adapter to use this method 

You can use a piece of small clear tubing to screw into the hole and use that for the tube test. It will seal itself in the threads as it's screwed in.
That's the only way to get a true reading. 

Even if its all new and set at 26mm it can  have a bad level ?

Maxbou92 wrote:

Even if its all new and set at 26mm it can  have a bad level ?

Yes.  

I've had some epic battles trying to get good fuel levels on older carbs.  I think it may relate to the floats not "floating" as well as they used too. And, of course, leaking float valves.   Anyway, take some clear tubing like Steve says, and grind a pencil point on the end, and screw them into the threads on the float bowl.  They may drip a smig, but not enough to upset what you are doing.

All right!!  Clear tube method and new plunger! Hope it gonna cure my low rpm bug. I appreciate guys

Maxbou92 wrote:

All right!!  Clear tube method and new plunger! Hope it gonna cure my low rpm bug. I appreciate guys

If you can wait, send your plungers to Zed.  His reasoning is sound.

 

Yes I will check this out!!