Ok..short history...I bought an 03 LTZ400 this spring...it has a full Yoshimira exhaust...other than that it is stock to my knowledge. This is my first 4 stroke ATV, and I am an auto tech...so I am not up to speed on the technical stuff on these things yet. It never ran great in my opinion...kinda stumbled off the bottom...sometimes would bog, and seemed to start harder and harder after owning it a few months.

I bought the factory manual for it...took the carb apart, and so far I have determined that the float setting was way off, but I was wondering if you guys in here could give me some basic jetting numbers and adjustment settings as a good starting point. The only legible number is on the main jet which is a 150. My last question is about the small vaccuum nipple to the above left of the fuel inlet from the petcock...does that small hose go to the other side of the petcock? I admit I got a little cocky tearing it apart and didnt make proper mental notes, lol.

Sorry..a little longwinded, but I would appreciate any help you could offer..THANKS!!

 

Its alright to get cocky lol...But what you def want to do because it isn't runnign right is def clean the whole carb out...the problem to me sounds like the carb being dirty and the valve needing to be adjusted...The stock main jet is a 130 on a z400 so a 150 depends on if you have an aftermarket airfilter or not and no lid or an airbox lid...I am not sure about how many turns out it needs to be I am guessing about 2.5 turns and the pilot jet should be higher then stock 22.5 is stock...Check the airfilter make sure it is clean,make sure all intake tubes are connected correctly, and check the valve clearance.


pic of carb
http://www.ronniesmailorder.com/fich...2994&year=2003

 

cocky is ok, I know what you mean about mental notes. i'm a diesel mechanic and I've taken things apart and forgot how it goes back together. but im still learning about my quad, never was good with carbs so like what was said before, sounds like to me it was jetted wrong. and welcome to the forums

 

Ok...I cleaned the carb pretty well...reassembled...still doesnt wanna start. Next thing on the list will be to check the valve clearances. I am still confused as to some of the settings in the carb..like the grooves on the needle, where should that be set?

As far as that vaccuum line I wasnt sure about, I am still not sure, but I plugged it into the other side of the petcock...I hope thats right.

Thanks for the help guys...i'll keep ya posted on the valve clearances, until then, if anyone has any more ideas, I am all ears, lol.

 

another thing the 03 models had problems with the petcock plugging . you might want to remove it and clean it. not sure what line your talking about but looking at the petcock the line on the left is the fuel line and the one on the right is the vacuum and it goes to the left side of the carb

 

Ok, I checked the valves and they were way out...the exhaust valves had too much clearance and the intakes were set at ZERO clearance!!! That was the starting issue. Set the clearences correctly and she fired up immediately. Now I just have to diagnose the running problem...still cant snap the throttle without bogging, it breaks up a bit when I rev it...and I noticed that when I first started it, within a few seconds I smelled the heat from the exhaust, the pipe was very hot, very quick...so I still have work to do, but at least I made some forward progress!

Thanks again guys, have a great holiday!!