Ltz 400 running lean

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endobear

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Last  March my wife's z400 started stalling on her unless she eased into the throttle. Didnt want to idle. Had to choke it a little for it to run worth a crap. Cleaned the carb a couple times with no change. Plug was looking a little lean.

Tinkering on it now I noticed a big ass hole in the muffler. Could this be causing it to run so bad and to be lean?

I also did a compression test. Warm, wide open. About 115psi. Added a little oil and it tested the same. Thinking my valves need some adjustment.  Could out of adjustment valves be the cause?

Been running the same jetting for 20 years with no issues. 

Att.spize909  " you got your ears on?"20240303_180740.jpg

 
Does the exhause crack and pop when coasting down a hill with throttle closed?

Does this bike have the vaccum diaphram slide carb?

 
Yes that is like running a wide open exhaust will lean it out for sure.

 
I would also clean the carb really well, jets and passage ways. Just helped fix my nephews LTZ400 that running lean from a plugged pilot jet.

 
Wash 10 Crew said:
Does the exhause crack and pop when coasting down a hill with throttle closed?

Does this bike have the vaccum diaphram slide carb?
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Not 100% sure but im pretty sure it was popping coasting, throttle closed. 

Yes it is the stupid vacume slide carb.

 
Realbadlarry said:
Yes that is like running a wide open exhaust will lean it out for sure.
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That's what I figured. 

I have another (almost) identical ltz 400. Going to pull that pipe off and put it on this one to see what it does.

Have a slip on muffler ordered. 

 
Did it sit for a while?Sounds like a plugged pilot jet i had same issue with my sons also would pop and backfire.Take pilot jet out poke a fine wire thorugh it reinstall

 
I’d guess muffler is more effect than cause. Thats my opinion after rebuilding airplane exhaust for 20 years that was run too lean. First thing it destroys is the exhaust and cylinder heads

 
Vaccum leak on the vaccum slide or just plane old everyday vaccum leak.  

Spray some carb cleaner around the carb when running and listen to engine RPM/sound.  

Had a KFX400 which is a LTZ dressed in Kawi green. 

Way back in the day, my ex-wife had one with cams, valves, comp, pipe, jet, ing box, 8 paddle haulers and ran pretty good, but final had to get rid of the vaccum carb.  She use to punk young bucks on 450's and smoke them.  

It does have a big cushy seat that was perfect to ride at the end of the day!

IMAG0188_3.jpg

 
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I had a Suzuki and the Orange Kawi... put quiet pipes on them, made the wedding veil mesh top for the air boxes, rejetted and put a small primary sprocket on them... they were sooo much fun... neighbor just sold the kawi and our friends still have the suzuki... no problems ever with them.  one had the white brother E2 exhaust can and the other the pro circuit quiet pipe....

 
Wash 10 Crew said:
Vaccum leak on the vaccum slide or just plane old everyday vaccum leak.  

Spray some carb cleaner around the carb when running and listen to engine RPM/sound.  

Had a KFX400 which is a LTZ dressed in Kawi green. 

Way back in the day, my ex-wife had one with cams, valves, comp, pipe, jet, ing box, 8 paddle haulers and ran pretty good, but final had to get rid of the vaccum carb.  She use to punk young bucks on 450's and smoke them.  

It does have a big cushy seat that was perfect to ride at the end of the day!

View attachment 98168
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The Ex right?

Hahahaa :pic:

Sounds like a vacuum problem like others have stated. 

 
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