GPz 750 ut A2 Anti Dive upper plunger unit

Hi everone,

my GPz 750 is suffering from seized Anti Dive Plunger Units (the upper unit pressed by the brake). Unfortunately this part is sold out and not a/v anymore from Kawa.

Since I dont want to put anti dive out of service entirely I was wondering if there is any way to overhaul the plunger and make the little piston movable again.
Tried WD 40 overnight with little success but the piston is still far from moving freely as it should.

Any ideas or hints on how to fix or where to get substitue?
Can the unit be dismantled somehow ?

Responses welcome
THX in advance

Howdy. Do you have the Kawasaki service manual? There's a pdf available that covers the 80-85 KZ/ZX750-4 chain drive models.
The anti-dive info is in the 1983 supplement section. The manual says do not disassemble the anit-dive unit & there's a test for the brake plunger, but any fixes require parts replacement, so you may have to try some disassembly, then use your own judgement.

Note: do not contaminate the brake fluid. Also, regular wd40 isn't really a penetrant, so you may need to try an actual penetrant.
I use the Liquid Wrench brand which has done good in several tests floating around the internet.

750turbo.com >>> Downloads >>> choose Full manual (128mb PDF) .
80-85 750-4 chain drive manual. Yellow/gold cover w color wiring diagrams. 1980-84 KZ750-4 & KZ700. 1983-85 ZX750.

martin_csr wrote: ................Note: do not contaminate the brake fluid. Also, regular wd40 isn't really a penetrant, so you may need to try an actual penetrant..

Exactly! WD40 is "Water Displacement 40th" formula. Using it to free up parts that are frozen in place is pretty much a waste of time. It works ok for its designed purpose, but that purpose is displacing water. For freeing up parts that are frozen together Kroil works extremely well. However, I don't know what effect Kroil might have on brake fluid friendly parts. Of course that's also true for WD40. Ed

Just an FYI. I said "regular wd40" as the wd40 brand now makes a variety of products, including a penetrating spray.
Liquid Wrench brand is probably still better, readily available & usually cheaper than the wd stuff.

Thx all!

What is the exact brand name of the penetrants you mention?

I havent seen those here in Europe yet.

MT

Eventually I found Kroil in ebay. Its apparantely a US product but a/v here as well. no problem.

Cant wait to test it.

thx for help!

Kroil is terrific stuff, but you must give it time to work. It is not an instant work stuff. I have used it for many years just don't expect it to work in a flash. If I have something that's really stuck or rusted it may take a couple of days to let Kroil do its magic.
Rick H.

Any penetrant will take time, depending upon the application. I've gotten good result from Liquid Wrench brand penetrating spray lubricant. The LW stuff is readily available in the USA at various places & it's inexpensive. LW silicone spray lubricant is another good product, and I also use their chain & cable lube on the motorcycle.

Rick H. wrote: Kroil is terrific stuff, but you must give it time to work. It is not an instant work stuff. I have used it for many years just don't expect it to work in a flash. If I have something that's really stuck or rusted it may take a couple of days to let Kroil do its magic.
Rick H.

Excellent point! On fasteners that were really stuck on my bike I soaked them with Kroil for 3 days, and I reapplied it each day. After that there was no problem removing the fasteners. Ed

Theses guy have a rebuild kit they sell if you need it . www.gpzzone.co.uk/

Indeed I odered a kid. That said, it only covers the LOWER part of anti dive unit which can be relatively easy dismantled and overhauled. The UPPER unit is the problem where a pin gets suppressed by brak fluid and this pin is most probably seized on all old used units and NOS aint available anymore.
Either way, next I will try out the penetrant to be delivered this week and we ll see.

Good news!
Eventually I managed to dismantle the Anti Dive's lower and upper unit completely, overhauled and reassambled it.
The plungers are now movable again under finger pressure as they should.
Will bolt on to the fork next weekend an dthen will see.

In fact dismantling is easier than expected (if you know how). Took me a good while to figure.

Lower Unit:
Ordered a resealing kit from GPZzone in the UK. It comes with all required sealings and O-rings and a new spring + a pretty good description.
So the lower unit is no problem to refurbish. Takes 30 min.

Upper unit:
Unfortunately, the above kit from GPZzone doesnt contain any parts for the upper unit (the one pressed by the brake) and the description keeps quiet on it.
I realized eventually there is a thread and the plunger unit can be unscrewed using a bolt with 14 mm wrench size. Just drilled a 6mm hole into the head of the bolt and with this it can be used as a kind of allen key to unscrew the unit (see picture).
The inner rubber O-Ring was seized a bid on account of debris and what not but no sign of corrosion. In lack of a new O-ring I cleaned everthing carefully made the plunger movable with a tin coat of silicon grease and that was pretty much it.

I am a happy man so far locking forward to undertake the ultimate road test ...