400EX jetting help
#1
11-29-1999, 09:43 AM
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I've added an FMF PowerCore4 to my 99 EX. I called them and they recommended going up 2 sizes on the main jet and up one size on the pilot jet. I have added the pipe, but not yet made the jetting changes. Over the Winter months I plan on modifing my airbox lid with six of the 1" vents. Since I haven't made jetting changes for the pipe yet I was wondering if anyone could suggest some main jet sizes to try out? I'm not even sure what the stock size main and pilot are? I'm located in Ohio at 850' above Sea level. Thanks for your help!
Bruce
99 400EX
99 Wolverine (4 sale)
Bruce
99 400EX
99 Wolverine (4 sale)
#2
11-29-1999, 01:22 PM
Bruce,
I would suggest that you pick up a shop manual for your machine..Clymer publishes a good one. It would tell you just about evrything you need to know when working on your bike and the book would pay for itself very quickly. For starters, the main jet is just inside the carb bowl..the little brass object in the center of the carb. On my Makuni, I have to remove the bowl to gain access to the jets or float. If your Keihin has a main jet access nut on the outside of the bottom of the bowl, you're one of the lucky ones. Just unscrew that nut to get at the main jet. At almost sea level, you probably have the stock main, unless you bought the quad used. I would go up one size fatter on the main right now for the pipe & test ride at 3/4 to full throttle for a performance check. Not necessary to do this in 5th gear, just use at least 3/4 throttle for 1/2 mile or so to detect any missing or cutting out.If none, you are jetted correctly for that part of the band. If you're going to drill out your airbox lid or change the filter system, you'll need to run at least one more size fatter, maybe two, to prevent a lean fuel mix. As to the pilot jet, I'd test the performance with the current jet first at idle to 1/4 throttle. That's where the pilot jet is functioning. After warm-up if it idles and runs clean up to 1/4 throttle you can leave it alone.If it were me, I'd just pick up three main jets fatter than stock. You may not need them now but if you do any other changes to the breathing of your ride you'll have them on hand. Here in Az main jets are only $3 so not a major expense. On my Warrior, I'm running four sizes fatter on the main with my air intake mods. I run stock pilot and needle jets & jet needle in the center slot & it runs like a turpentined cat
------------------
THE AZ HARD PACKER, calmiller@kachina.net
save the public land FOR you, not FROM you..join the Blue Ribbon Coalition online @ www.sharetrails.org
[This message has been edited by hot_shoe_cv (edited 11-29-1999).]
I would suggest that you pick up a shop manual for your machine..Clymer publishes a good one. It would tell you just about evrything you need to know when working on your bike and the book would pay for itself very quickly. For starters, the main jet is just inside the carb bowl..the little brass object in the center of the carb. On my Makuni, I have to remove the bowl to gain access to the jets or float. If your Keihin has a main jet access nut on the outside of the bottom of the bowl, you're one of the lucky ones. Just unscrew that nut to get at the main jet. At almost sea level, you probably have the stock main, unless you bought the quad used. I would go up one size fatter on the main right now for the pipe & test ride at 3/4 to full throttle for a performance check. Not necessary to do this in 5th gear, just use at least 3/4 throttle for 1/2 mile or so to detect any missing or cutting out.If none, you are jetted correctly for that part of the band. If you're going to drill out your airbox lid or change the filter system, you'll need to run at least one more size fatter, maybe two, to prevent a lean fuel mix. As to the pilot jet, I'd test the performance with the current jet first at idle to 1/4 throttle. That's where the pilot jet is functioning. After warm-up if it idles and runs clean up to 1/4 throttle you can leave it alone.If it were me, I'd just pick up three main jets fatter than stock. You may not need them now but if you do any other changes to the breathing of your ride you'll have them on hand. Here in Az main jets are only $3 so not a major expense. On my Warrior, I'm running four sizes fatter on the main with my air intake mods. I run stock pilot and needle jets & jet needle in the center slot & it runs like a turpentined cat
------------------
THE AZ HARD PACKER, calmiller@kachina.net
save the public land FOR you, not FROM you..join the Blue Ribbon Coalition online @ www.sharetrails.org
[This message has been edited by hot_shoe_cv (edited 11-29-1999).]
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