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2 wheels or 4 wheels?
We went riding yesterday, it was so hot that we just took it easy. I noticed that when we would just cruise around and then decide to open them up on a straight away mine would hesitate and sputter on the low end. The only way to get out of it was to shift down a gear or let it work its way through. I have never noticed this before. I was wondering if I should raise the needle in the carb. The second it gets out it, it runs great.
Let me know what you guys think.
Thanks
2002 KTM 400 EXC, this bike is awsome!
Quads I use to own:
FDO 463ex, Gas Gas 300, Gas Gas 450, Rancher, Yamaha Warrior, ATC Big Red.
If you can't afford to fix it or replace it, don't ask to ride it!
Top Dog
Raising the needle would be a good place to start.
440, Ross 11.5:1 piston, Web cam 479 grind, race port & polish, oversized valves, hardened rockers, CRF450 cam chain, 39mm FCR carb, lightened Flywheel, Stock clutch, WB CDI box, K&N filter , WhiteBrothers E-Series full exhaust, Sidewinder Chain, 15/36 gearing, open airbox, LSR Axcaliber +3.5 axle, Houser Racing +2 a-arms, Elka triple rate, fully adjustable front shocks, +1.25 Houser swingarm, Tag Metals X5 bars, Arens +1 steering stem, Muscle steering dampener, Stainless Steel brakelines, HeatSeeker temp. guage, Pro Design kill switch, DG Pro Series nerfs, 8 run Hauler paddles. ~~http://www.sounddomain.com/id/trick440ex~~
Yup,,,,raise the needle up,,or go up 1 size on your pilot jet and it should fix ya up....might have to make a minor adj. to your air screw..
Always wear your helmet!
This is happening on WOT thru the low end? If so, pilot and needle will have little effect.
Remember, the different circuits in the carb do not correspond to different RPM ranges, they correspond to different throttle positions.
What are your mods? It sounds rich to me...
Remember, at higher temperatures, air is less dense - this means your bike will run more rich than usual. The 400EX is known for a low-mid burble or skip if jetted rich on the main, or if the engine can't breathe well.
2 wheels or 4 wheels?
It was really hot and humid that day. I have not checked the sparkplug in a while to see how rich or lean it is for a while. I hasn't bothered at the track, but it has alwayed cooled down by race time and I run with the air box lid off. Which would help lean it out if it was running a little rich.
I think that I will check the plug first and if it is ok I will raise the needle next. Thanks for all the input.
2002 KTM 400 EXC, this bike is awsome!
Quads I use to own:
FDO 463ex, Gas Gas 300, Gas Gas 450, Rancher, Yamaha Warrior, ATC Big Red.
If you can't afford to fix it or replace it, don't ask to ride it!
Always wear your helmet!
If you're jetted to run with the airbox lid off, and cooler temperatures, you've just found your problem.
Putting the airbox lid back on increases the vacuum on the back side of the carb tremendously, this results in a MUCH richer mixture (think about how the choke works) that requires you to go many steps leaner on your main jet setting. Raising the needle will only compound the problem, making the "blubbering" happen at a lower throttle position.
It sounds like you're still trying to equate RPM to carb jetting - don't do it. You won't get it dialed in thinking in these terms.
Jetting ONLY equates to throttle position. If you're turning 1500 RPM (idle speed), but are at full throttle - you're riding on the main jet, not the pilot, not the needle. If you're turning 1500 RPM, but the throttle is closed, you're running on the Pilot.
2 wheels or 4 wheels?
So where does the needle fit in on the circuit? If the pilot runs the idle circuit and the main runs the WOT what does the needle do? Does it take care of the mid-range?
2002 KTM 400 EXC, this bike is awsome!
Quads I use to own:
FDO 463ex, Gas Gas 300, Gas Gas 450, Rancher, Yamaha Warrior, ATC Big Red.
If you can't afford to fix it or replace it, don't ask to ride it!
Always wear your helmet!
Not really midrange (in terms of RPM), but part throttle. Clip position affects from about 1/8 throttle opening to about 3/4 throttle opening at any RPM range.
Needle taper affects from about 1/4 throttle to full, having most of it's effect from about 3/8 to 5/8 throttle and slowly tapering off to full.
Hope that makes sense...
Top Dog
I'd like to refer to my personal feelings on jetting .... It blows.
440, Ross 11.5:1 piston, Web cam 479 grind, race port & polish, oversized valves, hardened rockers, CRF450 cam chain, 39mm FCR carb, lightened Flywheel, Stock clutch, WB CDI box, K&N filter , WhiteBrothers E-Series full exhaust, Sidewinder Chain, 15/36 gearing, open airbox, LSR Axcaliber +3.5 axle, Houser Racing +2 a-arms, Elka triple rate, fully adjustable front shocks, +1.25 Houser swingarm, Tag Metals X5 bars, Arens +1 steering stem, Muscle steering dampener, Stainless Steel brakelines, HeatSeeker temp. guage, Pro Design kill switch, DG Pro Series nerfs, 8 run Hauler paddles. ~~http://www.sounddomain.com/id/trick440ex~~
2 wheels or 4 wheels?
Gabe,
You were right, I took it down the road a little while ago. One way with the lid on and then the lid off. Once I took the lid off it was like turned on a switch, instant power!
I guess I remeber now that last winter I jetted up to compensate for the cold, and I never took it back down. I totally forgot about that untill tonight. I will have to get one of those Outerwares air box covers. With it being dusty I don't want to do much trail riding without it. Do you have any idea what they cost? or should I get the airbox vents?
2002 KTM 400 EXC, this bike is awsome!
Quads I use to own:
FDO 463ex, Gas Gas 300, Gas Gas 450, Rancher, Yamaha Warrior, ATC Big Red.
If you can't afford to fix it or replace it, don't ask to ride it!
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