Ltz 400 carburetor help - Suzuki Z400 Forum : Z400 Forums
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post #1 of 9 (permalink) Old 04-20-2019, 09:18 PM Thread Starter
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Ltz 400 carburetor help

Hi guys! New to the Ltz 400... just bought 2003 a few months ago and am still working on it... needed some help with a carburetor issue if someone could help... the picture is the clutch lever side of the carb and my Ltz would rev up high on idle and make suction noise and I found out that when I cover that nipple the sound goes away and the idle slows down but then when I put a cover over the nipple and try to start it it fires then immediately dies... can anyone offer some help as to what the nipple is and how to fix my problem? Thanks in advance
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post #2 of 9 (permalink) Old 04-20-2019, 11:00 PM
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That’s the vacuum hose that is supposed to go to the factory fuel petcok. Without it hooked up, your Z will only run in “prime”. Since the factory petcok fails quite often, most of us switch to a Raptor 660 petcok (which has an “off” setting) and cap off the vacuum line. Costs about $25 and worth every penny.
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94mm bbk, +4 stroker, Hot Cams, Vertex piston, FMF Power Bomb header and Power Core can, KW black diamond valves/dual springs, FCR39, K&N, Elka long-travel LT fronts and rear, Houser +3, +3/4 LT A-arms, American Star pro xs chromoly tie rods, Dyna non-programable, Tusk +3 axle.
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post #3 of 9 (permalink) Old 04-20-2019, 11:33 PM Thread Starter
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Thanks for the help! My z400 didn’t come with a vacuum pump... it’s just been the gravity... also my fuel selector options for my tank are “off on reserve” also... I did cap off that vacuum line with a pinched off hose and that’s when the quad wouldnt start... or start and die immediately I also only have 1 line on my petcock going straight to carb so I’m not sure if I need a breather hose but if I do I’m not sure where it goes

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post #4 of 9 (permalink) Old 04-21-2019, 01:20 AM
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Then your petcok has already been changed, so the vacuum port needs to be capped off. Now for the other problem, have you cleaned out the carb and petcok filter? Cleaned or replaced the air filter? Is it better with the choke on?

'05 Z
94mm bbk, +4 stroker, Hot Cams, Vertex piston, FMF Power Bomb header and Power Core can, KW black diamond valves/dual springs, FCR39, K&N, Elka long-travel LT fronts and rear, Houser +3, +3/4 LT A-arms, American Star pro xs chromoly tie rods, Dyna non-programable, Tusk +3 axle.
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post #5 of 9 (permalink) Old 04-21-2019, 09:29 AM Thread Starter
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The carb has been cleaned but I’m not sure I’ve heard of a percock filter where is that at? And yes I have a clean air filter... put one in a month or 2 ago and havnt rode more than 2 hours... I tried to run it with choke and it wouldn’t start... it fired once without choke then died instantly but has a much harder time firing at all with the vacuum capped off... thank you for all your help so far!

Last edited by Mjkelly5; 04-21-2019 at 12:09 PM.
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post #6 of 9 (permalink) Old 04-21-2019, 12:14 PM
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Itís the part of the petcok that is inside the fuel tank. You have to remove the petcok to clean it out, but thatís probably not your problem. The choke would give it more fuel, so itís probably already too rich. What jet sizes do you have?

'05 Z
94mm bbk, +4 stroker, Hot Cams, Vertex piston, FMF Power Bomb header and Power Core can, KW black diamond valves/dual springs, FCR39, K&N, Elka long-travel LT fronts and rear, Houser +3, +3/4 LT A-arms, American Star pro xs chromoly tie rods, Dyna non-programable, Tusk +3 axle.
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post #7 of 9 (permalink) Old 04-21-2019, 01:05 PM Thread Starter
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I’m not sure... whatever came in factory carb... I just think it’s weird that it starts up without the vacuum cap on but idles way to fast

Last edited by Mjkelly5; 04-21-2019 at 02:21 PM.
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post #8 of 9 (permalink) Old 04-21-2019, 04:24 PM
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Idling high and slowly surging describes a vacuum leak perfectly. Iím thinking either they tried to jet it to run with a vacuum leak or something is blocking airflow. Maybe the plunger diaphragm isnít lifting the needle or the needle seat is clogged, etc.

'05 Z
94mm bbk, +4 stroker, Hot Cams, Vertex piston, FMF Power Bomb header and Power Core can, KW black diamond valves/dual springs, FCR39, K&N, Elka long-travel LT fronts and rear, Houser +3, +3/4 LT A-arms, American Star pro xs chromoly tie rods, Dyna non-programable, Tusk +3 axle.
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post #9 of 9 (permalink) Old 04-22-2019, 10:26 AM Thread Starter
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I’ll take a look at the carb thank you for all the help
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