Krazy Katana

It's a digital electronic ignition (all Suzuki's with electronic ignition since 1987)
Later models have more sophisticated advance curve (instead of 'step' on early ones)
Advance starts around 1700rpm, air leak / lean mixture causes the idle problem
May need slightly bigger pilot jets?

It's possible. It has stock pilots but +3 mains. I'm going to be trimming the plug wires, measuring resistance in the plug caps, and pulling out the washers either tonight or tomorrow night. Depends on how much time I spend working on the 125 tonight.
On air leaks... I've tried spraying WD40 around the intake boots and airbox boots, with no change in idle. Should I re-attempt with carb cleaner?

Here's a shot of the setup on the needles. I pulled the two washers, trimmed the plug wires, and cleaned out caps. No multimeter, so I didn't check resistance. I used the "water in paper towel on header" test to check for firing, and all 4 are firing. Only got a short chance to run it, had to come in to watch my siblings while my dad went to flush the engine on our boat. Will be running and doing a quick shakedown later.
Also installed the "new" kickstand, which is on the bottom in the pic.

crazypj said:

It's a digital electronic ignition (all Suzuki's with electronic ignition since 1987)
Later models have more sophisticated advance curve (instead of 'step' on early ones)
Advance starts around 1700rpm, air leak / lean mixture causes the idle problem
May need slightly bigger pilot jets?

Click to expand...

is there an adjustable air gap?

There are adjustable pilot screws on the front of the carbs. All are currently set to 2.5 turns out.

I think he meant air gap on ignition reluctors.
No, it isn't adjustable
As for air leaks, check vacuum line to tank from #4 carb, it can crack on 'bends'
Make sure all the vacuum plugs on carb tops are in place plus the tiny washers under carb tops
Oh, there should be a nylon washer on top of clip to act as spring seat

Nylon clip is there, just didn't want to balance it on top for the picture. Vacuum line is good, and all o-rings under carb tops are ok and present.
I'm thinking that I might need to go up a step on the pilots. I can't get the damn thing to run below 2500, even when hot. Carbs are synced, and everything down to the throttle shaft seals were sprayed with WD to check for air leaks.
I did notice that cylinder 1 isn't firing well. Headers on 2-4 are HOT while 1 is more of a "very warm" after a solid 20 minute ride.

Do you have dual or single fuel line tap?
Suzuki gives a fuel flow amount in service manual, I made a new fuel connector for mine rather than wait 2 weeks for new fuel line

I believe it is a dual tap. Two lines come from the petcock (from a 750, but the same) then each line goes to a "T" which has one end in each carb (1-2 and 3-4).
Interesting you say that though, because I'm curious if the issue is in my petcock. It is used, and not super smooth to turn. I wouldn't be surprised if it needs the diaphragm rebuilt and a good cleaning.

Probably worth checking, doesn't take too long to remove and strip tap.
I've done it with couple of gallons of fuel in tank, need to temporarily 'seal' cap though or it leaks (shouldn't but breather is faulty on mine )

I noticed yesterday that anytime I came to a stop it just dropped off and almost died, but if I gave it a blip of throttle it would be fine and settle back in at 2500 or so

Internship and life have been taking up time, so not much spent working on the bike. Been riding it to work pretty much every day (not bold enough to ride in rain yet) and its running well, minus the idle and cold running. I think the issue is either in the choke mechanism (rail is bent, holding #1 open slightly?) or electrical (remember weak spark. New plugs bought to test). I'm thinking it's not the petcock failing to deliver fuel, since the same idle issues were present with the old pingel petcock. I decided to add some details to this post so that someone may be able to help me with troubleshooting ;D

Current Jetting:
37.5 pilot (stock according to Clymer) 120 main (+3 according to Clymer)
This is with the stock airbox, K&N drop-in filter, Vance & Hines exhaust. This is how I bought the bike (I have removed the washers under the needles which the PO put in)

Details about the cold running:
Bike hesitates on acceleration, sounds a bit off, sometimes it takes a couple good revs to 8-9k to clear up the running. After that it'll run well, except for some clutch slip. All of these issues go away after 10-15 minutes of riding or so. After that, I can pin the throttle and it'll pick up and go at any speed. There is a noticeable bump in acceleration when pinning it from a 3,000 rpm crawl. It doesn't hesitate, but it feels like it just sort of comes on the power way harder after a second. I believe this is because of the vacuum building in the carb, since I do not have pumps and they are CV carbs. Feel free to correct me if I'm wrong here.

Details about the dying on idle:
Bike idles well down to 2500 or so once warm. I believe that when I loosen the idle adjuster past that it is completely disengaging the throttle plate. At this point, (or any other point when cold that it feels like dying) it slowly putters out, tries to idle around 1000, then dies. At this 1000 rpm "idle" it sounds like only two cylinders are actually firing.

Check coils are not cracked.
I'm pretty sure I told you previously about coil fitting?
They look like they should fit with leads against frame brace but it is wrong and causes internal damage, usually with external cracks visible
or stress marks on outer body

You told Andoor in his thread, not me. I saw the message though, and made sure they are correct. Leads are opposite side of the coil from frame (Closer to carbs) and facing inwards. Did not notice any cracks, but will check when I have the tank off to check for spark.

Not much to update... Back at school waiting for the shop to open up so i can finish my gauge mounts. Been riding it to school every day and have had no issues. Runs well, starts with choke when cold, and without it when warm (improvement over starting fluid, which it used to take when cold). Still doesn't idle below 2,500. Coils are not cracked as I can see, and spark on all 4 looks strong. I did notice that cylinder 1 has much more black on it than 4, 3, and 2, which were all a nice tan. I recall the header on 1 being colder than the rest after a ride (not cold, but not nearly as hot as the others. It seems like the bike might be dragging 1 along at low rpms, but it is definitely firing well once it gets to higher rpms. I figure I'll need to pull the carbs to re-check float height, and my mixture screw settings.
And since I feel bad about the lack of photos, here's a shot with my roommate's bikes.

Next time you do a carb sync, swap the lines around to make sure everythuing stays constant. When they are set properly, if all cylinders have about the same compression , valve clearance, etc, the gauges should stay pretty much level. Any major variations when swapping vacuum lines between cylinders shows something isn't right

crazypj said:

Next time you do a carb sync, swap the lines around to make sure everythuing stays constant. When they are set properly, if all cylinders have about the same compression , valve clearance, etc, the gauges should stay pretty much level. Any major variations when swapping vacuum lines between cylinders shows something isn't right

Click to expand...

More often than not this scenario shows something isn't right with your gauges.

Yep, to check gauges just connect them one by one to a single vacuum source (usually number 3 or 4 cylinder on Suzuki's)
If you ever used the Suzuki 'ball bearing' gauges you had to set them every time you used them

Someone backed in to her AGAIN. Second time this year. Good news is there were only a few new scratches, but the mirror broke. I'm more bummed about my helmet getting jacked up, it was sitting on the right handlebar, and the bike fell on it. Tore up the finish on top, and now I'm a little paranoid that I should be getting a new one.
Also, I forgot my carb synchronizer back in Washington. I'll have to find someone around here who has one I can borrow.

Unfortunately the only safe reccomendation is to get a new helmet. Sorry to hear it man.