Honda TRX ATV Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
Hello all. I'm new to the forum and would like to know if the needle on the 400ex is adjustable. I'm running with a Lexx slip-on, K&N filter and an open air box. My main pilot is a 170 and the slow is a 42 with the air screw turned out 3 times. The bike runs, idles and pulls like a champ at WOT but when I took it for a test run (with a new plug) down the block I shut it off and pulled the plug the top of it was white as hell so I know I'm lean. If the main is too large could that cause the issue? Do I need a larger slow jet even though it starts and idles with great response? Turn out the air screw another half even if it's already turned out three times or buy an adjustable needle and set the clip where it needs to be? I know it's alot but I'm going riding tomorrow and I don't wanna be the one getting towed out of the woods. Any suggestions would be greatly appreciated.
 

·
Super Moderator
Joined
·
4,276 Posts
The pilot jet works in conjunction with the FUEL/AIR screw you identified as the air screw. That screw adjusts the amount of fuel mixed with the available amount of air for a smooth idle. If it idles fine, no adjustment is necessary.

The slide needle is the mid-range metering device. If it runs at steady throttle without loading up (like the choke is on) or surging (acts like it wants to go faster but can't), then it's fine and does not need adjustment.

Down the block wide open is not far enough to read a plug. The engine should rev to red line (hits the rev limiter) without bogging or surging. If you got a handfull of main jets, jet up in steps of two sizes till it bogs (runs like the choke is on) just before it hits the rev limiter, then back down 2 jet sizes from there.

No guarantee that you won't be getting pulled out, but it shouldn't be due to a running problem. You can still get flats, have a bearing go bad or break a cable.
 

·
Registered
Joined
·
15 Posts
True the 08 is not adjustable... I had a buddy of mine who works at a bike shop here in San Diego acquire one from an 02 they will fit the crab nothing has really changed. I usually do the color test when I jet. I put the engine under decent strain white knuckle pand out in a salt flat or something. Then i pull it back in to camp, and pull the plug, if it is clean as you know you are lean, if it is black as you know you are rich. What I look for is that smooth Milk Chocolate color. When i see that I know I have got it right, pay attention to the machine too, and get it dynoed for optimal performance....Hope that helped, and welcome..
 
1 - 4 of 4 Posts
Top