04 z400 start and idle issue - Suzuki Z400 Forum : Z400 Forums
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post #1 of 28 (permalink) Old 03-31-2017, 09:00 AM Thread Starter
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04 z400 start and idle issue

I can only get it to run when I have the throttle cable and idle adjust in one position. Fuel circuit is 2.5 turns out. And here's what's been checked/replaced.

Had intermittent spark, checked, replace cdi, checked 2 different coils on it, stator resistance was in spec. Spark is consistent, got it to high idle, backfire and make the pipe glow.

Cleaned carb, disassembled. Cleaned all 3 jets with bristle from a brush, carb cleaner and 100 psi compressed air. Cleaned all passages with carb cleaner and 100 psi. Removed top hat and diaphragm before doing this, checked needle movement by hand. High idle, had throttle cable adjusted far out to compensate dumping fuel, backfires. Only in pri- no start in reserve or on.

Replace petcock. Starts, idles around 900, still a little sputtering any touching of idle adjuster, throttle adjustment or fuel screw and will backfire or no start.

110 psi on cold compression test (yeah it's low but should still run)

Valve lash was on the high side on 1 intake valve but all within spec.

Reviewed all wiring and checked connections.

Timing looks to be on, very close to entirely lined up on cams and crank in position on compression stroke. I highly doubt my very close is anything other than a hair from perfect.

Has new fuel (dumped all old fuel, replaced and dumped again before this batch) but some debris on new petcock already so I'm going to seafoam it tonight. Jets were blurry and not 100% clean after pulling carb again. Has 20 -30 minutes of idle at various speeds with all tests performed and I'm at a loss.

Has an 05 or later tps carb with no tps installed, I have tape over it for now, doesn't seem to be pulling in any air from there.
Air filter is clean and functional, new spark plug gapped properly.

What am I missing? I leave for hatfield and mccoys on Wednesday and I need this working. Anyone have any input? It'd be much appreciated and will help community in return. Long Island New York
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post #2 of 28 (permalink) Old 03-31-2017, 09:01 AM Thread Starter
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High idle was 16-1800
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post #3 of 28 (permalink) Old 03-31-2017, 09:13 AM Thread Starter
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Same issues with gas cap removed and gas cap vent is working, sorry about multiple responses but trying to give all info to the gurus
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post #4 of 28 (permalink) Old 03-31-2017, 10:06 AM
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stock carb ?

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03 ltz400,95.5bore,+5crank,P&P,13.7:1,JE piston,spacer plate,RHC +1 intakes valves,RHC #208in&187ex cams,DRZ manual decomp,DID cam chain,no air box,Sredrum TB 42mm FCR,RAT stack,WB fuel screw,EMN needle,quick shot,06 clutch 450r drive plates w/trx400 ex springs,C2HB,ex thumber,trx450r air boot, Barker Performance pipe, trailteck flywheel,dynatek,NOLOGY HOTWIRES ,nerf bars,450r shocks, +4 swinger,lowered front & rear
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post #5 of 28 (permalink) Old 03-31-2017, 10:49 AM
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Replace the pilot jet. If stock carb just go with a 25 and turn the screw in some.
It runs with the new petcock on ON now?

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post #6 of 28 (permalink) Old 03-31-2017, 12:45 PM Thread Starter
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I bought it from a backyard mechanic, I believe it's an 05 or later carb due to the tps provision and notch in the butterfly on that side, the stock in 04 appears to just have a gold colored cap over it. But yes it is a stock carb. I had a 22.5 and a 25 pilot in it and the results are the same. Yes it runs in the on and reserve positions with the brand new petcock ordered from local Suzuki dealer. Any adjustments and it stalls and is hard to start unless in the sweet spot. Thanks guys
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post #7 of 28 (permalink) Old 03-31-2017, 01:05 PM Thread Starter
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Float is operating properly and no fuel leaks. Maybe clean everything out again and new fuel, also try shimming valves. It really seems like a carb issue but I can't put my finger on it 🤔
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post #8 of 28 (permalink) Old 03-31-2017, 01:13 PM Thread Starter
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I have a 130 main jet installed and the 25 pilot. I have a 140 and 22.5 on the shelf that I've tried in different combinations but the 130 and 25 seem to work best. I don't know what size the starter jet is but I've cleaned it. It's sooooo close to being right but I'm missing something
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post #9 of 28 (permalink) Old 03-31-2017, 02:13 PM
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if you have removed the air box lid ,then you will need to change main jet

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03 ltz400,95.5bore,+5crank,P&P,13.7:1,JE piston,spacer plate,RHC +1 intakes valves,RHC #208in&187ex cams,DRZ manual decomp,DID cam chain,no air box,Sredrum TB 42mm FCR,RAT stack,WB fuel screw,EMN needle,quick shot,06 clutch 450r drive plates w/trx400 ex springs,C2HB,ex thumber,trx450r air boot, Barker Performance pipe, trailteck flywheel,dynatek,NOLOGY HOTWIRES ,nerf bars,450r shocks, +4 swinger,lowered front & rear
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post #10 of 28 (permalink) Old 03-31-2017, 03:44 PM Thread Starter
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It's factory with no holes in it, the exhaust has the silencer removed, like someone cut it off the exhaust tip so there's a 2 inch opening, which is why I'd imagine it came with the 140 jet. Even with a lean condition it shouldn't be this hard to keep running. I wish it was at the point where I was sizing jets and checking plugs
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post #11 of 28 (permalink) Old 03-31-2017, 10:27 PM Thread Starter
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Ok I cleaned out tank, petcock carb and got all the disgusting brown WooterWooterWooterWooter and tin foil out 100%. Started idled a little better, go to adjust again boom same thing. Recheck valve clearances, .102mm on intake side. .254 mm on shifter side exhaust and .203mm clutch side. Thoughts on shim time?
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post #12 of 28 (permalink) Old 03-31-2017, 10:27 PM Thread Starter
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Manual calls for .10-.20 mm intake and .20-.30 exhaust? Pics in album of timing for giggles

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post #13 of 28 (permalink) Old 04-01-2017, 12:55 AM
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Quote:
had throttle cable adjusted far out to compensate dumping fuel, backfires.
Don't quite understand this. Why was fuel dumping?
Is the vaccum line good?
I think it is still dirty/restricted.
Are the jets new?
Does the choke help?
If you crank the fuel screw out more, does it help?

2007 LTZ 400.. 94mm J&E piston, +4mm hotrods crank, 536webb cams,wiseco valves, 39mm fcr, tokyo mods throttle spring, honda thumb throttle,spring removed. yoshimura full exhaust, honda 400ex intake tube, no air box

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post #14 of 28 (permalink) Old 04-01-2017, 06:29 AM Thread Starter
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When I had the throttle adjusted out the petcock was completely shot, since it's been changed I was able to tailor it way down. At that point the fuel screw did nothing I'm guessing because I could only keep it running at 16-1800 rpm. I'm using a used 25 pilot and a new 130 main. I'm unsure of the starter jet size
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post #15 of 28 (permalink) Old 04-01-2017, 07:42 AM Thread Starter
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.254 on the one tappet is bugging me. Why would 1 valve be .05 different different? The other 3 are down to pretty much min spec. I wonder if it's hung up.
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