KZ400 - project (stuck vac pist!)

Hi All,

I've been posting in the various forums (engine/elect/body) about a project bike i picked up, but figured this forum was the best place to post this specific question.

I took off the carbs (THEY ARE A NIGHTMARE)...

- varnish all in bottom bowls
- i think one carb is missing a needle!

but the biggest problem is that one of the vac pistons is STUCK!

i've sprayed in some 10w40, but that is not doing much (also took of a primary jet to spray where the needle is)....

do not want to hammer at it.... but what can i do??

just soak in 10w40 and hope for the best?

see the pic below...

thanks....

- prime

Howdy there Primemover. The slides( pistons ?) on my CV36s' were stuck like yours. I sprayed some PB Blaster on'em, reached in with a pair of closed needle nose pliers to act as a fulcrum in the bore at the bottom of the slide, then used a thick standard screwdriver to pry them upward. This sounds crude and it is, but if the slides don't move the carbs are junk anyway. Once I got them to move a little, I sprayed more Blaster on 'em, then kept prying them up, then tapping them down, they kept becoming more and more free until I was able to remove them. I used a stone to clean up the slide bores by honing them slightly. Probably a fine 3M scratch pad would be better. Strangely, the slides were fine, the bores had corroded slightly. Once I cleaned them up, they slide freely. I had nothing to lose so I used this method. Good luck with yours !

Gotta love that PB Blaster. Good stuff. I work on "saltwater" outboards for a living, and I am never without it.

PB Blaster is great! It says it will rejuvinate seals, or rubber? I tried it on the caliper piston seal on the brake. Mmmmmmmm.. The Blaster rejuvinated it alright. It's like Viagra for rubber!:laugh:

That o-ring had no chance to fit in the caliper again, it was so big and puffy:lol:

But is is good stuff to use on stuck parts.

I love PB Blaster. This stuff will eat through a styrofoam cup. I've used it a lot. I used it on my rear spring u-bolts on my ol Dodge truck after I scratch brushed off the dirt. I was able to save both u-bolts and the nuts. This stuff rocks.

AND...........you can get it at Walmart.

Hey...

never heard of the stuff (untill now!)...

bought a can and sprayed it in (still waiting for it to work)....

i did find it odd that on the can it showed 3-4 pictures of what LOOKED like a cup (melting in various stages!)...

i guess i now know why...

it MELTS CUPS?!?!?

should i be concerned about being around the stuff??

"should i be concerned about being around the stuff?? "
Nah ! Don't seem to affect humans in that manner, just styrofoam cups. Odor is a little strange. I would be really careful about where the arrow on the top of the spray button was pointing. I wasn't careful once with a can of carb spray, got me right in the eyes. It turned out ok, but sure was painful.
Oh ! And one other thing on the carbs. If you pull tthe choke butterflies off the choke shaft, working in the bore is a lot easier.

Post edited by: 50 bucks, at: 2006/01/12 03:55

Hey there....

used that PB Blaster and a pair of needle nose pliers (as you suggtested)....

pushed them in below the pistion, pried them open...

moved the piston a little, so i pushed the piston back down and kept repeating....

after a few tries, was able to pull pistion out!

thanks....

though i did learn something else....

Carb clean appears to do a REAL NUMBER on rubber (o-rings, rubber plugs)....

oh well, live and learn!

hmm, those were stuck bad, as i said in the other thread you posted, a few taps on the side of the carb and they were free. Looks like this is a common problem with these carbs... how long was your bike sitting for? Mine was sitting since 92

how long sitting...

no FREAK'N idea...

but, did find an old insurance/reg card burried under the seat....

dated:

12/81

!

whether or not this was the LAST TIME it was registered, i do not know (but suspect it was)....

i think the bike sat for at least 10-15 years...!

YIKES!

Hey there back ! Glad to hear the method worked for you. You know, I've been thinking that if you made a thin wedge out of some tough material, you could tap it into the bore to get the piston moving also. Maybe a tough wood like Oak or Walnut would do the job.
Your experience with carb clean on rubber parts brought up an incident from years ago when I was a car mechanic. Seams a fellas' master cylinder was low on brake fluid, so he remembered someone had told him that kerosine would work as a replacement. He tried it. We replaced every component in that hydralic system except for the steel brake lines, which we flushed clean. Some rubber parts in it was lookin spongy, so we didn't want to take a chance of the rest spongi-fyin, hence the complete rebuild. Never seen such icky lookin crap in a system in my life.