Z400- rejetting for high elevation Question

[hollamby]

Hello all,

I am just getting into the atv world and new to carbs. I have always had fuel injected snowmobiles and motorcycles.

Anyways, I have done a lot of reading on the subject but having a hard time with the high elevation here in Colorado. Most people ride lower and there settings are very different.

I ride roughly 7,000 to 10,000 elevation. I know that it will need to be rejetted depending on riding at 7,000 vs 10,000. I am just looking for a starting point.

The quad is a 2003 LTZ400 everything stock. It has a 130 jet in it with stock carbs. When running at 8,000 to 9,000 ft is is rather boggy in 3rd, 4th, and 5th. If I am climbing a hill it will bog to the point of stalling. I understand if I remove my air lid that will lean the machine out. So if it is running very rich already and I lean it out with the air filter do you think that this would be a good starting point before rejetting?

The plug is completely black. In 1st and 2nd it doesn't run that bad. I don't hear any poping with accel or decel. I read that you should drop down one main jet size for every 1750 to 2000 feet of elevation you go up (info for Mikuni carbs). True? Seems I would be down very low though.

Just looking for any type of help. I don't plan on putting a exhaust on this quad because I am going to buy a new 09 LTZ in the spring. So the jetting settings would be for a completely stock ltz with possible the airbox lid removed. Just trying to get it set for summer time riding with the eleveation. But I want to get this one runnning good so I can pass it to my girlfirend.


Last quick question. If I adjust the carbs for 8,000 ft and then start it at my house (6,000 ft) am I causing harm to the quad. I don't plan on driving it at my house that much I am just talking about loading and unloading it from my truck.




Thanks!!!!

[KAWIRYDER]

I live in Montana and ran at about the same altitude and I did have full yoshi exhaust, K&N filter no lid,rev box and I believe i was running a 145 MJ. I would try getting smaller jets and do a plug check to where it was right on the edge of running lean at your house.

[cataway]

i'm inclined to think that if you just run with out a air box lid should be very closes to were you would want to be.

if it still seams to be rich pull out the spark arrester, if thats permisable or maybe in faver of a after market one.

[hollamby]

Well I ran it today at around 9,000 at 65 degrees. And the gears felt much stronger but fourth and fifth it was still boggy. The plug is a little dark still.

Should I go down slight more? Or do I have to mess with my fuel screw?

[cataway]

and if youu put the lid back on it gets worse? changing jets is easy,maybe a 125 andno lid.

another factor is the intake boot ,getting a ex boot is going to get you more air=more power

[hollamby]

I ran it again at ~10,500 ft and the quad felt even better.

So I am confused with what the bike is telling me. The higher I go the better it seems to run so it is saying the less air it gets the better...but the plug is telling me rich (not enough air)

I am going to try the 125 and see what it does.

This elevation **** makes me want and go get a fuel injection reall bad because once I get it figured out for 10,000 ft then when I ride 7,000 it is going to be very different. I guess it is worth it though to ride in the mountains.

Thanks.

[hollamby]

Originally posted by cataway
and if youu put the lid back on it gets worse? changing jets is easy,maybe a 125 andno lid.

another factor is the intake boot ,getting a ex boot is going to get you more air=more power

See this is where it is weird. With the lid off it was extremely boggy.

I am starting to think that I have a problem some place else with vaccuum or a craked fuel line or something because the results are all over the board and don't make conherent sense.

thanks for the help,
Ryan