Fellas,
I still haven't had a chance to test it out, hopefully tomorrow. It's still apart because I'm wiring in a teather switch and can't figure the positive lead on the coil. I posted another thread asking for help, you may have seen it.
Hopefully I'll get the info I need and get it together tomorrow. As for the staked butterfly screws, they may be but mine came out quite easy. Just make sure the carb is off the motor so you don't have one fall down the intake. That would leave a mark!!!

 

you can just splice it into your red button killswitch wire on your left handlebar side thats what i did and it works just fine

 

Is this HP improvement for 400EX's only??, I wonder if it will work on my 200SX??, if so, any help??

 

Well I got a chance to test it out last Friday at a mx track that I ride alot. This was good because I had good referance points on the track to judge it. I definately noticed an improvement. Mostly in the mid-range and top end. It seemed to pick up rpms faster in the mid-range. It also lofted the front easier off small rises while on the throttle.
I would realistically rate it at about one to two pony gain. I looked at another posting and some guy flow benched the carb with and without the butterfly and said it made a pretty big flow difference. They also said they did it to a stock motor and got about 1/2 horse on a dyno, about 1.2 horse on a modded motor.
My vote it, it's easy, it's free, it ran great, I gained power--seems pretty self explainitory

 

Thanks Roadracer96, everything seems to make sense (and horse power!)
Being down here in Florida, I don't think I'll miss the choke. Although I think I'll keep all the hardware and directions for reinstallation for the annual trip to Pennsylvania for Cochranton's poker run. [img]i/expressions/face-icon-small-cool.gif[/img]

 

well i tried the choke plate thing and my bike ran like crap. it needed rejeted. i didn't have the jets handy so thats a later project.just wondering if anyone else had to rejet.i have aftermarket pipe,440kit,advance timing key. any suggestions would be helpful.

 

Hey JP400, Did you let it warm-up?[img]i/expressions/face-icon-small-shocked.gif[/img]

 

Yea-

I took the choke plate out as well and my 400ex ran horrible. When I took the air filter off (giving it more air) it ran like a charm-... and SUPER gain in power. When switching to 2nd gear the front tires pull off the ground as if I was in 1st. Anyway- due to the excellent air/fuel mixture with the air filter off that tells me I need to rejet to a SMALLER jet. I'm running a K&N 165 main jet right now.

Does that sound right to you guys?- jetting smaller? Anyone else rejet their bike after taking the choke plate out?

 

I think I've got a 164 in before and after the mod, air fuel screw 3 1/2 out. Runs great, mixture seems good on plug checks. It's been in the 80's and 90's here for temp lately with fairly high humidity.

 

Wow. That's cool everyone. So, you all say it's a great gain in performance? I might have to check into that. I'm always looking for more power out on the track.