Jetting Info at Altitude???

mattxoaaron · 07-26-2011, 02:19 PM

I'm sure this ? has been asked before , but I could not find the info I needed anywhere. I need to know what jets to install and what turn on air screw.

2005 Z400
HMF Slip On
K&N Filter...lid off
Everything else is stock

I'm riding at 5000ft in Idaho

PLEASE HELP!

ridin434 · 07-26-2011, 02:48 PM

Buy a jet kit, like a dynojet. They you can play with it, and get exactly what you want. Also buy a 25 pilot to swap in.

I am in MN, but we have similar mods, just a little bit elevation difference. I am running a DJ 146, needle second clip, and fuel screw around 2.5 turns out, but I adjust it everytime i ride so it runs nice. It just takes a lot of riding and messing around with the fuel screw to figure out what works. I have an adjustable fuel screw from a site sponsor here, which if your messing around with jetting, this will save you tons of time over finding a tool that will fit under the carb to adjust while its running. I just adjust on the fly after everything is warmed up, a 1/8 turn at a time until its running strong.

I find the temp/humidity has a lot to do with how my wheeler runs, but as I have it set right now I can take any of that variance out with just a quarter turn of the fuel screw, at the most.

As for being at a higher elevation than I am, I would imagine you may need to downsize a jet size from what I am running. Also don't forget I have an adjustable needle (which comes with DJ kit), and it isn't set where most people have it.

My MX mechanic friend suggested switching that rather than the jet (not sure why, think at the time it was easier than pulling the bowl off the carb).

From what I have been told, adjusting the clip on the needle is about one jet size difference, correct me someone if I am wrong.

In the long run, you are best off buying a jet kit, rather than buying a few jets and not getting the right size the first time. Also any further changes to your wheeler will be easy to rejet without another trip to the store, and since I see your in Idaho, your winters are a lot cooler than the summers. You will already have the jet size you may want to install in the winter for riding.

If anyone disagrees with what I am saying feel free to add some constructive criticism to my set up. This is what has been working for me all spring/summer.

mattxoaaron · 07-26-2011, 03:23 PM

Thanks for the fast reply. I was looking at getting a DJ kit down the road, but a big group is riding this weekend and I was looking at just buying jets for a quick tune. I figure with as many people on here that some one has to have the same set up...

ridin434 · 07-26-2011, 05:36 PM

How is it running right now? If it is running fine, and has been for awhile I wouldn't mess with it before a big ride.

Have you been on any rides with it set up the same as it is now?

You may be able to adjust your fuel screw, and not even open up the carb for your ride coming up if it is running close to correctly. The fuel screw is easy with the correct tool.

mattxoaaron · 07-26-2011, 05:41 PM

I just finished the inatall last nite..I'm headed out right now to do some runs on it.. I just figured with the new pipe and intake that a jet change would be needed. A few threads that I read said that it would be needed.

ridin434 · 07-26-2011, 06:03 PM

Before you take your carb off or apart, play with you air box lid a little.

Take it off, ride a little. It will be leaner.

Put it on, ride a little. Will be richer than before.

I would say you will have to go up at least one jet size. You have a Mikuni 130, if it is stock. If you are buying Mikuni jets I believe you will have to go up one, maybe two sizes.(135 or 130) Again, someone correct me if I am wrong.

This will give you a good start on your jetting and getting the feel of having a rich enough airflow.

I have found when I was learning to jet my wheeler that using the airbox lid on and off helped determine whether being rich or lean. adjusting the fuel screw also makes a drastic difference. I don't know how I rode for years without even knowing about it.

mattxoaaron · 07-26-2011, 09:05 PM

Just got back from a 15 minute ride. I drove around for a few minutes letting it get warmed up first. After 2-3 minutes I ran it up thru the gears at medium throttle and everything ran fine. Did it again and same result. So I up'd to 3/4 throttle keeping the tires on the ground as much as I could and it ran fine. So I went straight to full out run thru and she was perfect. I did a few 1,2,3 gear runs and let it die down to 3rd gear lull and full throttle ran it and she never skipped or sputtered. So.....I'm just gonna leave it alone.

The person that I bought it from ran it at the dunes so it might have been messed with on jetting before. Not sure. I just figured it would need to be changed from stock settings due to the after market parts. Oh Well......Fingers crossed for this weekend.

Thanks for helping out ridin434,

Matt A

venom44 · 07-26-2011, 09:12 PM

how do i make a post??

07-26-2011, 02:19 PM	#1 (permalink)
mattxoaaron :::Rookie Rider::: Join Date: Jul 2011 Posts: 8	Jetting Info at Altitude??? I'm sure this ? has been asked before , but I could not find the info I needed anywhere. I need to know what jets to install and what turn on air screw. 2005 Z400 HMF Slip On K&N Filter...lid off Everything else is stock I'm riding at 5000ft in Idaho PLEASE HELP!

07-26-2011, 02:48 PM	#2 (permalink)
ridin434 :::Z-250 Rider::: Join Date: Aug 2010 Location: Deerwood, MN Posts: 441	Buy a jet kit, like a dynojet. They you can play with it, and get exactly what you want. Also buy a 25 pilot to swap in. I am in MN, but we have similar mods, just a little bit elevation difference. I am running a DJ 146, needle second clip, and fuel screw around 2.5 turns out, but I adjust it everytime i ride so it runs nice. It just takes a lot of riding and messing around with the fuel screw to figure out what works. I have an adjustable fuel screw from a site sponsor here, which if your messing around with jetting, this will save you tons of time over finding a tool that will fit under the carb to adjust while its running. I just adjust on the fly after everything is warmed up, a 1/8 turn at a time until its running strong. I find the temp/humidity has a lot to do with how my wheeler runs, but as I have it set right now I can take any of that variance out with just a quarter turn of the fuel screw, at the most. As for being at a higher elevation than I am, I would imagine you may need to downsize a jet size from what I am running. Also don't forget I have an adjustable needle (which comes with DJ kit), and it isn't set where most people have it. My MX mechanic friend suggested switching that rather than the jet (not sure why, think at the time it was easier than pulling the bowl off the carb). From what I have been told, adjusting the clip on the needle is about one jet size difference, correct me someone if I am wrong. In the long run, you are best off buying a jet kit, rather than buying a few jets and not getting the right size the first time. Also any further changes to your wheeler will be easy to rejet without another trip to the store, and since I see your in Idaho, your winters are a lot cooler than the summers. You will already have the jet size you may want to install in the winter for riding. If anyone disagrees with what I am saying feel free to add some constructive criticism to my set up. This is what has been working for me all spring/summer. __________________ 2004 z434 CW 434 400EX boot HIDs Lexx w/ FMF Powerbomb head pipe Longhorn Clutch lever w/reverse OSHC's DRZe kit YFZ calipers Last edited by ridin434; 07-26-2011 at 02:54 PM.

07-26-2011, 05:36 PM	#4 (permalink)
ridin434 :::Z-250 Rider::: Join Date: Aug 2010 Location: Deerwood, MN Posts: 441	How is it running right now? If it is running fine, and has been for awhile I wouldn't mess with it before a big ride. Have you been on any rides with it set up the same as it is now? You may be able to adjust your fuel screw, and not even open up the carb for your ride coming up if it is running close to correctly. The fuel screw is easy with the correct tool. __________________ 2004 z434 CW 434 400EX boot HIDs Lexx w/ FMF Powerbomb head pipe Longhorn Clutch lever w/reverse OSHC's DRZe kit YFZ calipers

07-26-2011, 06:03 PM	#6 (permalink)
ridin434 :::Z-250 Rider::: Join Date: Aug 2010 Location: Deerwood, MN Posts: 441	Before you take your carb off or apart, play with you air box lid a little. Take it off, ride a little. It will be leaner. Put it on, ride a little. Will be richer than before. I would say you will have to go up at least one jet size. You have a Mikuni 130, if it is stock. If you are buying Mikuni jets I believe you will have to go up one, maybe two sizes.(135 or 130) Again, someone correct me if I am wrong. This will give you a good start on your jetting and getting the feel of having a rich enough airflow. I have found when I was learning to jet my wheeler that using the airbox lid on and off helped determine whether being rich or lean. adjusting the fuel screw also makes a drastic difference. I don't know how I rode for years without even knowing about it. __________________ 2004 z434 CW 434 400EX boot HIDs Lexx w/ FMF Powerbomb head pipe Longhorn Clutch lever w/reverse OSHC's DRZe kit YFZ calipers

07-26-2011, 03:23 PM	#3 (permalink)
mattxoaaron :::Rookie Rider::: Join Date: Jul 2011 Posts: 8	Thanks for the fast reply. I was looking at getting a DJ kit down the road, but a big group is riding this weekend and I was looking at just buying jets for a quick tune. I figure with as many people on here that some one has to have the same set up...

07-26-2011, 05:41 PM	#5 (permalink)
mattxoaaron :::Rookie Rider::: Join Date: Jul 2011 Posts: 8	I just finished the inatall last nite..I'm headed out right now to do some runs on it.. I just figured with the new pipe and intake that a jet change would be needed. A few threads that I read said that it would be needed.

07-26-2011, 09:05 PM	#7 (permalink)
mattxoaaron :::Rookie Rider::: Join Date: Jul 2011 Posts: 8	Just got back from a 15 minute ride. I drove around for a few minutes letting it get warmed up first. After 2-3 minutes I ran it up thru the gears at medium throttle and everything ran fine. Did it again and same result. So I up'd to 3/4 throttle keeping the tires on the ground as much as I could and it ran fine. So I went straight to full out run thru and she was perfect. I did a few 1,2,3 gear runs and let it die down to 3rd gear lull and full throttle ran it and she never skipped or sputtered. So.....I'm just gonna leave it alone. The person that I bought it from ran it at the dunes so it might have been messed with on jetting before. Not sure. I just figured it would need to be changed from stock settings due to the after market parts. Oh Well......Fingers crossed for this weekend. Thanks for helping out ridin434, Matt A

07-26-2011, 09:12 PM	#8 (permalink)
venom44 :::Rookie Rider::: Join Date: Jul 2011 Posts: 1	how do i make a post??

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