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View Full Version : Power Problem With 400ex


300EXRD
04-29-2005, 08:46 AM
I HAVE RECENTLY REBUILT MY 99 400EX AND PUT A HIGH COMPRESSION 11:1 PISTON IN IT AND IT IS BORED .080" OVERSIZED BUT I AM NOT VERY HAPPY WITH IT'S PERFORMANCE
DOES ANYONE HAVE ANY IDEAS. ONE IDEA I HAD WAS MABYE THE CAM WAS OFF A TOOTH BUT I DONT KNOW ?
cals400ex
04-29-2005, 11:12 AM
what other mods you have done to the bike?
300EXRD
04-29-2005, 01:42 PM
I have got a weisco 11:1 piston, k&n air filter, re-jetted the carb,
and I have a gt thunder full exhaust system that is it
RiderTRX400ex
04-29-2005, 01:49 PM
what do you have for your main jet... you might have made an error somewhere when jetting... maybe your to lean or rich?
also.. what do u have for a headgakset in it
300EXRD
04-29-2005, 03:18 PM
I have a 165 main and a 42 pilot. For a head gasket i have a Tusk gasket from Rocky Mountain Atv
2004exrider
04-29-2005, 04:56 PM
check your spark plug a 165 sounds way to lean. i have a k175 in mine and its still got the stock bore with stage 1 cam and air filter and slip on exhaust. also what stage cam do you have? yours might be to small for it.:cool:
Mobile Dyno
04-29-2005, 07:39 PM
I have a 440 with Wiesco 11:1 comp, White Bros. XC cam, TwinAir filter with the Air box lid off. I have a Dynojet jet kit in. I put it on the Dyno with the A/F and I ended with a Dynojet 170main, Needle on the 2nd clip, 40 pilot, and mixture screw 3 turns out.
RiderTRX400ex
04-30-2005, 11:25 AM
no headgasket leaks?
300EXRD
05-02-2005, 05:42 AM
I don't seam to have any headgasket leaks. I am running the stock cam. This weekend I'm planning on useing a wide band 02 sensor to tune the carb it reads the actual air/fuel ratio.
2004exrider
05-02-2005, 09:00 AM
ive been hearing a lot about those lately, just wondering where you can get them, and how does it all hook up? also whats the price:confused:
300EXRD
05-02-2005, 11:53 AM
You can get them at Jegs all you have to do is weld in a bung in your exhaust for the sensor and supply power and ground to the monitor. You can even hook a lap top to it if you have on to log all of the info,but they cost around $400.00
400xe1999
05-13-2005, 06:45 AM
how quick does a normal 400ex top out at. and also how fast does it go??????????????????????????:devil:
prepracing
05-15-2005, 04:17 AM
stock cam ? that would be the main problem. Any kind of aftermarket cam will help out the overbore high comp. pistons performance. Then some porting and polishing on the head will make it all come alive !