Staking / Flaring screw ends (updated)

I removed the carbs (CV34's) from my ZN700 initially to do a quick clean-up and unstick the float needle on the #2 carb, but figured since I have them off I might as well (yet again:S) do a thorough cleaning of them.

I completely disassembled and cleaned them, then replaced all of the o-rings (for piece of mind) that I could locate.
Now I'm in the process of reassembling them, but I'm at a slight stand-still.
How in the heck do you "stake" (as refered to in the FSM) the screws that hold the choke and throttle venturi plates in without bending the shafts all out of shape? :huh:
I actually did slightly bend one shaft while removing the screws, but seem to have it straightened out enough that it doesn't seem to bind while rotating it in the carb body.
The threaded ends of the screws are slightly hollow and have notches in them to stake/flare them, and the FSM shows what looks like a pair of standard pliers to perform this, but really doesn't mention the exact procedure.

I've gotta have my ZN up and road-worthy before Sept 27th when we head out to Vegas for the BikeFest, so I really could use some help and advise here folks.

Post edited by: RetroRiceRocketRider, at: 2007/09/03 02:33

It isn't easy to stake the little 3mm screws as you have figured out. I don't bother. I use 3mm JIS standard screws with lockwashers and a touch of Loctite. The purpose of staking is to ensure that the screws don't come out and go into your combustion chamber. The lockwasher and Loctite serve the same purpose. I can't think of a great way to stake the screws since it has to be done with the butterfly in place and as you have noticed, the shaft CAN bend when you attempt to punch a screw going through the venturi. The screws used by Keihin are purpose built and as noted, hollow so it may be a whole lot easier to do using those (not sure where new ones could be found).

Thanks for the quick reply and info WG!

I'm aware why they're staked, as I've encountered a few of the small Honda and B&S motors I work on regularly with badly gouged cylinder walls from this, which is the prime reason I'm concerned about getting those little buggers to stay put.

Since Kawi doesn't list those screws seperately, I have no clue as to their length.
So obviously I'm going to need to get slightly (perhaps 1mm) longer ones since the lock washers will require that, which I can figure out at the fastener specialty store near me.
Now, should I use red (high strength) Loctite or the blue (med strength)?
And will the Loctite be able to withstand the constant barrage of fuel/air mist without breaking down, possibly allowing the screws to loosen up?

Post edited by: RetroRiceRocketRider, at: 2007/08/21 14:02

I honestly can't remember what length the screws are. I use JIS screws with the lockwashers built onto the screw for this purpose... I use BLUE Loctite and they will not loosen up. I am afraid that if RED is used, the screws will need to be drilled out and with a small hole, if you damage the thread, you would need to recut thread to 4mm and that would put a MUCH larger screw in that place... I think that in JIS screws, they measure the overall screw length (rather than the threaded part) once you get below a certain length. I think mine are 6mm length but will check. I buy them by the 100s so don't order them often and have to check my records or the bag to remember.

Thanks again for the info WG.

I'm off to the fastener supply shop now to see if they have any of those JIS screws in stock (crossing fingers). That way I can finally get these carbs back together and on the bike, then move onto to tackling the leaky valve cover gasket, cam plugs and bevel gear case gasket. :S

what if you take a screw driver and pinch it in a vice then have a good helper hold the rack of carbs down on the screw so the end of the screw head is on the screwdriver then you stake the end from the top. would this work?

I don't see why that couldn't work.

My big worry though, would be the pressure not being equal on both sides of the screw while doing this.
This could possibly could bend the choke rod and/or damage the choke plate, and those rods are expensive ($56!), if they're even still available anymore.
I imagine that's why the manual shows some type of (special?) pliers being used to stake the screw via crimping, rather than being impacted with something.

It's defiantely something worth considering though, but I'm going to need to see if there's a way of keeping the pressure equal before even attempting it.

Thanks for the idea flht1997.

i'd think if the vice and screwdriver are solid, and the carbs are help flat and straight against the tip of the screwdriver that when you whack it not much should move, except the screw deforming that is.

The rod that the butterflies sit in has a slot where the butterflies are inserted and there is very little actual material. I personally would not stake them with a screwdriver EVEN if I could find the proper screws which are no longer available. The ends of those screws were made for the purpose... a little hollow on the end so they would flare.

I just wanted to post an update on my throttle and choke plate screw situation.

I picked up some screws and lock washers and loctited them in there per WG's suggestion, and everything is A-OK in that area now.....Yeah!

But even after straightening the throttle shaft in the #1 carb that I bent during the disassembly of everything, the throttle still binds and won't return closed without being "persuaded" manually.

So now I'm in need of the #1 throttle shaft (must be for the #1 carb, since each carb throttle shaft has a completely different external throttle linkage) for a Keihin CV34 carb.

I'd gladly order a new one through Kawi, but they don't even offer them seperately. So I'm hoping one of the good folks here with a spare set of CV34's being used for parts can help me out.

These style of CV34 carbs were used on the KZ750 Spectre, as well as just about every early 80's KZ750 inline-4, and probably other bikes that I'm unaware of.

So can someone help a :S guy get his "baby" back on the road before BikeFest on September 27th?