400EX jetting help..
#1
02-25-2019, 11:27 AM
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400EX jetting help..
just got a 400ex on Saturday it’s an 04. Seems like it’s running very lean. When I bang through the gears it keeps backfiring when I let off. I’ve ordered a new carburetor for it because the current one is very very Dirty and the machine has been sitting for a few years according to the owner! So I got a replica Klein carb off eBay for 50 bucks with a warranty if I wanna return it and rebuild the stock carb. Anyways, my 400ex has no air box lid, has a CT racing header and CT racing slip on exhaust, I’m located on Long Island in new York and my elevation where I ride is around 30-50 feet above sea level. Thanks for any help I can get!
#3
02-25-2019, 10:02 PM
Range Rover
#4
02-26-2019, 07:22 PM
I am. That old KeiHin OEM carb is worth a lot, even dirty. If not corroded or damaged physically, it is FAR better than a new Chinese replacement. Clean it!
Backfiring out the exhaust on off-throttle deceleration is a feature of low-restriction mufflers. Reducing inlet air-flow resistance with a pod filter can also contribute to a lean condition. Plug-reading and possible rejetting is called for here.
Backfiring out the exhaust on off-throttle deceleration is a feature of low-restriction mufflers. Reducing inlet air-flow resistance with a pod filter can also contribute to a lean condition. Plug-reading and possible rejetting is called for here.
#5
02-28-2019, 05:02 AM
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I am. That old KeiHin OEM carb is worth a lot, even dirty. If not corroded or damaged physically, it is FAR better than a new Chinese replacement. Clean it!
Backfiring out the exhaust on off-throttle deceleration is a feature of low-restriction mufflers. Reducing inlet air-flow resistance with a pod filter can also contribute to a lean condition. Plug-reading and possible rejetting is called for here.
Backfiring out the exhaust on off-throttle deceleration is a feature of low-restriction mufflers. Reducing inlet air-flow resistance with a pod filter can also contribute to a lean condition. Plug-reading and possible rejetting is called for here.
if this is a good place to start?? Advice is very much appreciated!
#6
02-28-2019, 10:51 AM
#7
02-28-2019, 11:41 AM
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You can get a set of 10 diff KeiHin pilot jets on eBay for less than the cost of one from the dealer. Over 40 for the size sounds good, but also those really small jets get clogged easily. As for the main, you can up it somewhat, but you may want to first try lowering the needle clip one position.
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#8
02-28-2019, 12:02 PM
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#9
02-28-2019, 01:25 PM
#10
02-28-2019, 05:06 PM
Range Rover
There was a pipe shoot out Dirt Wheels March 2001that had the main at 160 for the ct pipe but also came with their needle and different pilot which they didn’t disclose. I’ve seen a lot of people suggesting a 42 pilot which was eliminating the need for a choke to start the bike but I’ve seen as low as 3/4 turn out to 2 3/4 turns out on the fuel mixture.screw using the 42 pilot. Being an 04 you should have adjustable needle would try lowering 1 notch like sr.ruedas suggested 2nd from bottom.