TOPIC:

I recently decided to do a full rebuild of the carbs on my Z1R (Mikuni VM28SS x4). I've done basic cleanings before, spraying carb cleaner in the passages and replacing worn needles, but this is my first time taking them all the way down to pieces.

I noticed that there are several places that obviously should have some lubricant, and a few places that seem like they might like some. The factory service manual only mentions putting grease on the main throttle shaft.

So two questions for you folks: What, if any, parts should be lubricated. And what's the right product?

The throttle shaft has bronze bushings in the rack, and a narrow spot on the shaft which I'm assuming is intended to hold grease. There are also the ball ends on the slide-to-throttle-shaft links.

But how about the choke plungers? How about the throttle slides themselves? Those are both metal on metal. Should I put them together dry?

I poked through my shelf full of greases. I have a least three different wheel bearing greases, four different brake greases, and SIL-Glyde and Lucas while lithium and Super Lube (regular, not silicone). And for light oil I have 3-in-One and Hoppe's #9 gun oil. And then the spray cans... And on and on.

So I had this in mind:

For the throttle shaft and slide linkage, I thought I'd use CRC Brake Grease ("for all metal-to-metal contact, with moly, PFTF, & graphite, plastic & rubber safe")

The choke plunger shaft seems to drag in the metal cap, so maybe a tiny amount of SIL-Glyde under the rubber top cap? (silicone-based, compatible with plastic and rubber (EPDM & Nitrile))

For the throttle slides, maybe just a light swipe of 3-in-1 or Hoppe's. Or maybe WD-40 or boeshield t-9? Or maybe find a spray dry film lube of some kind? Whatever is there probably won't last long in the presence of gasoline, but it would be nice to avoid sticky slides. Or scoring the slides. They are pretty shiny still.

I know how everyone loves pictures, so here you go:

I personally like your lubrication ideas with one exception. I would not put any lubrication on the throttle slides. They will remain happy and unscored for a long time if they ingest nothing but nice clean air. As you said you don't want anything "sticky" on them to trap abrasive material on the surface. JMO, I do not rebuild carbs for a living, but have done a few over the years.

I love Z1Rs BTW, a motorcycle that was definitely ahead of it's time!

Mike

hi all yes good points about lubrication i always put anti seize copper slip on all the air jets air fuel screws you only get one chance with them before your in trouble,david

Don't use any lube anywhere except the throttle shaft , maybe a wipe of anti seize on the brass air screw threads and some lube on the rubber fuel tee's to aid assembly.
Oil or grease on the slides and plungers will just get washed off with fuel or attract dust and grit .

Have to agree with Zed on his comments. To prove a point, a while back I bought a set of carbs for my KZ-1000 that were supposedly rebuilt. I noticed when the throttle return spring was disconnected that the carbs seemed to operate in a sluggish manner. At first I thought well, maybe I should put something on the carb slides to slick them up a bit, but decided against this idea. I reinstalled the return spring and just lubed the spots already pointed out and put the carbs on. Ran the bike for about 100 miles and had to take the carbs off to replace the choke plungers. I noticed the carbs operated much more smoothly than when I first installed them. Now did they smooth up from just use or did some gas vapors help to lube the slides in the bores? I have no idea, but I am glad I didn't jump the gun and put any lube on the slides which most certainly would have attracted dirt and caused other problems.
Rick H.

In addition to what's been said I use some dry teflon lube on the choke actuation shaft bushings after it's all assembled. The dry lube won't attract dirt.

Be sure NOT to mix parts between carbs! Parts tend to wear together and mixing parts can create problems. Ed

650ed wrote: Be sure NOT to mix parts between carbs! Parts tend to wear together and mixing parts can create problems. Ed

So far I believe I have managed to keep the slide assemblies, needles, and floats associated with the correct body. I think...

Also, as has been pointed out, I was also considering the choke actuator shaft (aluminum on steel) and the fuel inlet pipes, but forgot to mention those.

Nessism wrote: In addition to what's been said I use some dry teflon lube on the choke actuation shaft bushings after it's all assembled. The dry lube won't attract dirt.

You'd prefer that over grease? Can you recommend a specific product. I might be able to find some space on my shelf for one more thing...

For the fuel inlets, I bought machined aluminum replacements with o-rings. The original center tee has been leaking on and off. I tried to test fit the new parts and they are not going in without some help.

What should I use on those? SIL-Glyde? I also have some food grade o-ring grease for my water filter. It seems like whatever I use will be washed out by fuel eventually, but it needs to be compatible with the o-rings.

I had not considered putting anti-seize on the air screws. I've never had a screw stick, but they are exposed. That would also need to be o-ring compatible. I use the silver Permatex anti-seize, but that does not seem likely to be rubber compatible.

And here is another topic. The manual says to use a non-permanent thread locker on the rack-to-body screws. Thoughts? I have some Loctite 222 , which seems fine. But I usually go the other way and use anti-seize because I hate stuck fasteners. But would the thread locker seal the threads and help prevent corrosion?

So summary:
Round slide: No lube, clean with carb cleaner, install dry
Throttle shaft: CRC brake grease on bronze bushings
Choke shaft: dry teflon lube?
Choke plunger shaft: nothing?
Fuel Tee and coupler o-rings: ?
Air screws: ?
Rack screws: ?

krazee1 wrote: I love Z1Rs BTW, a motorcycle that was definitely ahead of it's time!

I agree. Part of what attracted me to the Z1R was that the styling is so far outside of what was common in 1978. Sort of the opposite really. It's all angles, where a normal '78 KZ1000 or KZ650 or CB750 was all curves. It seems like a bold experiment that wasn't really popular at the time, but turned out to be a pretty good prediction of where the early 80s sport bikes ended up. That and after riding my dad's Z1R, I never really felt the same about the kz650 I had at the time.