TOPIC:

Hey guys, so I have a 78 KZ1000 that has a 4-1 kerker and individual k&n pod filters.

Can any of you guys give a sort of base to get started on getting it tuned? What size jets and settings used for pilots screws, etc. Engine us stock, I believe

These carbs have both the air screws and fuel screws. Not sure how to go about tuning with both

You have Suzuki carbs from as GS model .
Are they 26 or 28mm.
As a rough guide you want around 115 to 117'5 mains with those carbs.
Leave the rest stock and obtain some air corrector jets.
These are m5 grub screws with a 0.6 mm drilling and they fit in the air bleed to the emulsion tube ( needle jet holder) to richen up the off idle flat spot..
The fuel mix screw ( under the carb) on those carbs is very sensitive .
Start with it at 1/8 turn out and the air at 1-1/4 to 1/3/4 out.
You can actually close off the fuel mix screw altogether and they will act just like Z1000 carbs.

They are likely Suzuki carbs and will be VM26SS. Very few sets of Suzuki carbs that are 28s or 32s. I personally would set the jet needles to 4th clip position and try some 115 mains and 17.5 pilot jets. I would try 1 3/4 turns out on the pilot mix screw; be VERY careful as the tip size is super small and the hole the tip fits in is very small and if you even snug the pilot mix screw, the tip will break off in the hole it fits in. I would go 1 1/4 turns out on the air screw. I have had good luck with this set up. The air and pilot mix screws were the Suzuki way of providing fine tuning for smog test reasons (my guess here). You may want to measure the venturi on the carbs as they stuck similar assemblies on Kaw 650s with both air and pilot screws and these are VM24ss.

Thanks guys! I'll pull a float bowl off tomorrow and see what's in it. PO said he was running it and riding fairly good distances. Had the photos to prove it. Hopefully I look in there and what's currently in it is in the ball park!

Currently, I'm having a hanging idle and some popping

Lordzacharious wrote: Thanks guys! I'll pull a float bowl off tomorrow and see what's in it. PO said he was running it and riding fairly good distances. Had the photos to prove it. Hopefully I look in there and what's currently in it is in the ball park!

Currently, I'm having a hanging idle and some popping

Currently, I'm having a hanging idle and some popping

Possible causes for hanging idle could among other things include :
(1) air leak through cracks in old hard worn out carb holder(s);
(2) needed adjustment/lubrication/cleaning of throttle cable and inside throttle casing on handlebar (when throttle is closed, all carb slides are supposed to fully reach their bottom, where a noticeable "click" can be heard) ;
(3) automatic advance unit hanging and failing to return to idle position (perhaps needs inspection/cleaning/lubrication);
(4) needed adjustment of pilot air screw (where so equipped);
(5) needs timing adjusted (where owner-adjustable).

Popping through exhaust on deceleration can sometimes be caused from too lean pilot air screw adjustment, or a too lean pilot circuit due to whatever reason.

Backfire through carb(s) can result from too tight intake valve clearance, or failure of intake valve to fully seal for whatever reason when supposedly closed. In this event, some of the combustion from inside the cylinder escapes through the supposedly closed intake valve through the intake port and on out backwards through the carb.

Good Fortune!

What Patton said plus low coil voltage which causes the spark to be weak even when using good/new ignition components.
See this write up:
wgcarbs.com/index.php/using-joomla/exten...-categories/89-coils

Other possible hanging idle causes:
1. choke plunger pads hard and not sealing. Jiggle choke lever when idle hangs to see if it goes away. If it does, the plunger pads are shot.
2. No slack in throttle cable(s) - You should be able to stick your finger on the cable down by the carbs and deflect the cable some.
3. Cracked sync fitting rubber covers
4. Carbs need serviced as pilot circuit remains dirty
5. Believing anything a previous owner claimed about the bike

Well, I haven't been able to mess with it as much as I would have liked to here lately, but I did manage to look at it today.

So, for the mains, it currently has 120s on it, the pilot jets are 15s. I'm not entirely sure what the thoughts were when going with that setup, but pulled the plugs and they're pretty black. I'll try to attach a pic of the first one I pulled out.

So looks like I'll need to order some jets. Ordered some new plugs. Air filters are clean. I'll try the new jets 9ut and run some propane around to see if I can find an air leak. Disconnected the throttle cables with no difference, advanced seems to be fine, and though there is evidence the valves were adjusted, I'll probably check the clearances anyways.

Good idea. What are the plugs gapped to?
Steve

I'll check as soon as I locate one of the billions of those gap checkers floating around that's never there when I need it haha.

I should have taken a different photo, but this plug in the photo I dropped like a buffoon, so I think it landed and bent the ground electrode. None of the others looked like that.



I checked the 26s that originally were on my KZ900, it has 17.5s. Should work on these no problem, right?

Also, if anyone wants to source me where to order for the nians, that's be helpful, so far I'm looking at sudco and jetsrus, but it's a plethora of various jets. Want to make sure I get the right ones for sure.

www.chapmoto.com/mikuni-kn100-604-large-...-jet-parent-342-1561

So, I'm in the middle of cleaning up the 115s and 17.5s that came off my KZ900s original carbs, but in the meantime, I replaced the plugs with new 8ES s and set the gap to .030. Made sure the wires were in place well and fired it up.

Running pretty good now, wasnt hanging in idle or popping/missing.

I'll replace the jets hopefully tomorrow and see how it goes

I think my tach is hanging now though