Free POWER NOW Mod, What up?

59 replies to this topic
  • jmiakaike

Posted January 30, 2003 - 02:32 PM


The template is correct, slightly longer than the original powernow. The top part of the 'T' is farthest away from the slide and that is what locks into the rim. the plate may taper a bit down to the slide AFTER the bell, depending on the throat of your carb.. (some are tapered more than others, i made it so it can be filed down for a close tolerance to the throat of the carb, but not touching it)
the pictures are of the ones others have made, chris did his with some tips from me, but no drawing..

i hope this clears up some of the confusion



A big thanks to David for his work in creating the .pdf file and the templates!

  • tctrailrider

Posted January 30, 2003 - 02:59 PM


Picked up a piece of brass flat stock from the hardware store today, $2.10. Used tin snips to cut it and a file to smooth out the edges. It was a simple process, less that an hour and it looks great. Thanks for the info. photos etc. I also think the diagram for the James Now template is incorrect. I cut the slits in the bell with a hacksaw blade and marked the brass with a sharpie pen. Just eyeballed it all and it worked fine. I had enough brass for three or four tries so the pressure was off. Very easy to do, thanks again. Only two more months before the snow melts.

  • jmiakaike

Posted January 30, 2003 - 03:29 PM


guys.. i made the plate from a copy of an original power now.... the thing may be a 1/16" or two off in width but can be filed down to fit fine, i don't have micrometers to give an exact measurement.... it is longer, as i stated above...

the template is from me, the pics from toyrona and chris from oz....

how is the template wrong? :) :D

  • tctrailrider

Posted January 30, 2003 - 03:47 PM


Jmia, thanks for all of your work on this. As for the template issue it looks, from the photo's that the plate stops at the front of the bell. The template is some what of a T shape, and the top of the T would have to extend in front of the bell, towards the motor. The carb. side has to get smaller to fit into the opening. When I did mine, rather than to have the T, I notched this area out and it is smaller rather than larger than the rest. I also eyeballed and cut, got a good fit but did not measure it. My bike is a 2002 WR426. A 250 or 450 may have a different set up.

  • jmiakaike

Posted January 30, 2003 - 03:53 PM



ahh.. now i see where the confusion is.. the top of the T should be away from the motor.. that is what locks into the top and will not allow it to move forward, toward the motor,.. and yes, since each bike is slightly different (250,400,426 etc) you would file the part that extends towrad the slide on the edges to taper it to fit the carb throat.. so in reality, the bottom of the T is not the same width as just below the top of the T...

the photos are not from me.. they are someone elses.. the template is mine... :)


  • yamaha.dude

Posted January 30, 2003 - 08:51 PM


PDF Mark III is ready for downloading... hopefully this clarifies the different approaches to the same thing...



  • jmiakaike

Posted January 30, 2003 - 08:57 PM


the link didn't work..


  • yamaha.dude

Posted January 30, 2003 - 08:59 PM


you have to be quick around here... LOL I put comma com instead of dot com

Now it will work...


  • jmiakaike

Posted January 30, 2003 - 09:01 PM


one more time david.. you have .con not com.. lol

and looks awesome!! thanks alot!

  • yamaha.dude

Posted January 30, 2003 - 09:40 PM


FFS - Fat Finger Syndrome... LOL

The spelling checker didn't pick that one up...



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  • Chris_from_Oz

Posted January 30, 2003 - 10:53 PM


Hi David, just checked the new PDF, I noticed the caption on ToyRona's pic's say it is a longer plate extending into the airbox, it is actually extending towards the carb' slide in the carb's intake throat. I have an identical plate now installed in my bike, it extends 12.5mm past the bolt-up face of the 'bell, thanks, Chris. :)

  • yamaha.dude

Posted January 30, 2003 - 11:32 PM


Thanks Chris, where would I be without my team of proof-readers... LOL



  • Math

Posted January 31, 2003 - 04:17 AM


Sorry to bother you guys but I have to ask that newbie question and I hope you'll accept to satisfy my curiosity.

As I said many times, I'm nothing like a mechanic :D but I would like to understand what you guys are trying to do :). What is this T-shaped plate for and how is your mod improving the engine performance?

If any of you wishes to redirect me with some links to already written explanations, I will be happy to do my homeworks :D.


  • MN_Kevin

Posted January 31, 2003 - 04:52 AM


The Power Now divides the air horn in half...or two chambers per-se, an upper and lower.

At low throttle openings, this divider plate allows (the same vacuum) that normally draws off the ENTIRE area of the air horn to now draw off HALF (the lower half) of that same air horn. This results in GREATER VELOCITIES drawn from the lower chamber ONLY of the airhorn into the carb throat.

Greater air speeds means better atomization of fuel AT LOW THROTTLE OPENINGS AND REDUCES the typical 4 stroke lag (offset by a PROPERLY operating accelerator pump jet) often associated w/ 4 stroke engines. When the throttle (and slide) are > 1/2 open, the carb is drawing off both the upper and lower chambers of the airhorn the Power Now creates.

You may have read where a smaller carb is installed to increase low end torque. A large carb increases top end HP. The KTM 125/YZ125 have a large carb for sheer top end HP, AT THE EXPENSE OF LOW END TORQUE.

This is due to the venturi size (inside diameter) of the carb.

  • Math

Posted January 31, 2003 - 07:25 AM


WOW! :)

Thank you very much for this clear answer NH Kevin!

  • jmiakaike

Posted January 31, 2003 - 10:24 AM


now email that explanation to
hey, you get your head back yet? sending mine in soon... :)

  • pdx_drz400

Posted January 31, 2003 - 12:36 PM


If you leave both chambers open, the air speed wouldn't change because you have the same volume of air going through the same total opening. You would have half in one chamber and half in the other-but the speed would be the same. The only way the air speed would increase is if you closed off one chamber and forced all of the air through a smaller opening (conservation of mass). But that would also be a restriction so the total air volume would be less. Am I missing something? Has anyone seen any dyno test results yet?

  • jmiakaike

Posted January 31, 2003 - 12:49 PM


true.. but remember, that as the slide is rising, the top half of the opening is blocked by the plate. what this also does is stop the turbulence caused by the air that hits the slide and is deflected downward in to the airstream going under the slide into the engine... so you now have the same engine vacuum acting on HALF the original carb venturi volume at any position below half throttle... the other chamber opens as the slide passes the plate at the halfway point.. is intended for low down power and response not all out HP...


  • WR_Dave

Posted January 31, 2003 - 05:17 PM


Thanks for the input guys, just imagine the trouble you would have if you were trying to mfg. these units. Seriously, I really appreciate your efforts. $80.00 U.S. is about $150.00 Cdn and I can use that cash elsewhere. WR Dave.

  • MN_Kevin

Posted January 31, 2003 - 05:38 PM


hey, you get your head back yet? sending mine in soon

It is on it's way to NH RIGHT NOW!!!


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