Keihin Carbs Reassembly 1980 KZ750 Ltd

Missing 1 fraggin butterfly plate screw! Anywhere to get one? HELP! Edited lots.

Per this size and thread pitch guide, Metric and JIS are the same up through 8mm bolts, but it doesn't describe those below 2mm.
www.boltdepot.com/fastener-information/m...ic-thread-pitch.aspx

The rubber boots - blue threadlocker on those new hex bolts from another post, and to screwdriver torque on a clean head. Using acetone for perfect clean. Answered my questions searching.

Reassembling after a few years of BMX racing. Bike uncovered and cleaned. I think o-rings were bad between the carbs. A neighbor blew cigarette smoke through them to show where my vacuum problem was. Searching for all the parts... History:

Carbs pissed 2012. Attempts and worsening of engine. Rebuilt carbs and found air fuel needle in 2 or 3 was broken, fell through a passage to the butterfly valve choke area. Unsure if air blaster removed it. I would like to try other carbs if this doesn't run.

Rebuilt valve body, seats machined and new shims to spec. Pistons and rings measured spec. Transmission left alone as it shifted like a dream. New electronic ignition. Counted timing chain 3x and reviewed Clymer 3x just to be sure. Vac rebreather removed to troubleshoot.

Didn't start on rebuild. Neighbor specd carbs and I shelved it with stuck rubber boot nuts. Learned from BMX restoration that acetone and automatic transmission fluid 50/50 is the best and final resort with ferrous rust and cold weld. Bolts finally removed and I stalled.

Still need to peen the screws and install the butterfly valves w red threadlocker..

Charging the battery.

Original thread on screws/threadlocker.
kzrider.com/forum/3-carburetor/604014-ch...0h-ltd-1980?start=12

You don't need loctite on the carb boot screws.

And in case you are in need, these are the various O-ring sizes for the carbs.

Pilot Screw: 1.2 x 2.6
Pilot Plug: 1.5 x 2.8
Fuel Transfer Tubes: 2.0 x 5.5
Drain Screws: 1.4 x 4.0
Float Bowl: 2.0 x 67

I lost a screw to the carb butterfly plate. Have 7 of 8 now... anyone have ideas or new stock?

Per Wikipedia, "Standard ISO metric screws and nuts will interchange with JIS metric screws and nuts, but due to tolerance differences, they cannot be torqued to full specification when mixed. True ISO metric screws are more likely to strip the threads out of tapped JIS metric holes."
en.wikipedia.org/wiki/Talk%3AISO_metric_screw_thread

SOOOOoooO I need real JIS spec screws.
Check out this really well documented rebuild. There are tips in here I've never seen before.
litetek.co/Guide_Keihin_Rebuild.html

After all these yeqrs you are still helping.. thanks!

Nessism wrote: You don't need loctite on the carb boot screws.

And in case you are in need, these are the various O-ring sizes for the carbs.

Pilot Screw: 1.2 x 2.6
Pilot Plug: 1.5 x 2.8
Fuel Transfer Tubes: 2.0 x 5.5
Drain Screws: 1.4 x 4.0
Float Bowl: 2.0 x 67

Nessim, always there with answers. In a previous post your jpg were no longer present. Thanks for posting O-ring sizes. I just finished that a few years ago when you helped me last. Now I've lost a damn screw. Any resources or buy a size bigger to be able to flange them? Thx.

I found these...
www.belmetric.com/4mm-c-10_74_1343_1349_...jis-zinc-p-8204.html

www.kohler-engine-parts.opeengines.com/i...nfo&products_id=1764

The choke sticks now. I can't see anywhere there is any contact. Before reinstall of the choke plates everything returned when the choke lever was pushed. Reassembly was done carefully so as not to bend the rods.

I know the return spring is notoriously weak on the CV34 - is there an aftermarket suggestion? It seems like the thin gauge return spring wire gets caught in the rod system there and pushes the plates off their intended alignment. Something needs to hold that return spring from bending all wonky. Pictures once I get mobile.

Admittedly, I cleaned the butterfly plates and thus my numbers off. I have the plate stopper nubbins facing in to the carb body.

Loosen up the butterfly screws and play around with alignment of the plates until there is no binding. You might have to loosen up the carb gang bracket screws too. Once you get everything aligned nicely the butterfly's will close properly.

Edit: the attached photo shows the left carb butterfly plate misaligned; look at how the dimples in the plate are not equal distance from the shaft. This is case in point of what is mentioned above.

Good eyes! I wondered the same but didnt want to touch the rack. Couldnt even see straight after all that fuss. All 8 loosened and plates reseated. Gang bolts on 2 carbs.

I ended up twist tie oaround the return spring coil and that did the trick! It was seating in a gap and fracking the system. I also inserted a fat o-ring and cinched it with another to spread the two choke bars like the 2 springs in the throttle balancing rack.

Carbs seated and 50-76mm stainless clamps used instead of those damned springs! WINNER! New rubber really takes the stress out of this.. saves a ton in beer money.

Balanced carbs back to throttle opening evenly along all 4 butterfly, but there seems the sliiiightest play in the rack at rest before engaging all 4 to the carb left of the throttle carb looking at them. ..

Going back on.. but PETCOCK! Filled the tank and it leaks out the fuel line in ON position, which should be vac sealed right? Maybe cuz I didnt have the end cap on the vac line of petcock? Thx here we go!

Nessism wrote: Loosen up the butterfly screws and play around with alignment of the plates until there is no binding. You might have to loosen up the carb gang bracket screws too. Once you get everything aligned nicely the butterfly's will close properly.

Edit: the attached photo shows the left carb butterfly plate misaligned; look at how the dimples in the plate are not equal distance from the shaft. This is case in point of what is mentioned above.

Closing thread as CV34s are reassembled. Post moved to new thread for tuning to remove all my nonsense about lost screws, etc.