i.d size of various jets

3 replies to this topic
  • nut

Posted August 24, 2006 - 06:11 PM


in the spirit of the do it yourselfer i'm thinking i can ream out the i.d.(inside diameter) of the stock jets to meet my requirements for tuning. especially after i pull the potato out of my pipe and tear a hole in the airbox. gotta love the epa. so where can a guy find the dimensional requirements for the various sizes? i can make any that would need to be reduced in diameter as well. yes i'm trying to save a few bucks, gotta pinch it were you can. thanks all...

  • xr_man

Posted August 25, 2006 - 08:35 AM


just drill them according to to markings ....so a 150 main jet is 1.5mm a 170 is 1.7mm etc
they are not marked according to flow ....like some carbs ....so its easy

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  • OneToGo

Posted August 25, 2006 - 05:54 PM


I would not advise drlling jets.
Just one scratch in a jet can alter flow rates- it has been noted on these forums before..
They are not expensive and you know exactly what size you are putting in.
When you change MJ jet you may be looking at avery small range of sizes eg: 165/168/170/172 are in common use on the WR 450.
Each is noticeably different on the bike and I doubt you be able to get the accuracy required by drilling compared to OEM unless you have access to right machine tools - then you may have a chance.

  • nut

Posted August 26, 2006 - 04:07 AM


thanks for the size tips i can figure it from there. i am a aerospace machinist by trade so holding tenths tolerances and fine finishes is something i do every day, and yes it does take the right tools. one of my good friends is a screw machine guru and he has made jets and fuel mixture screws for fat performance in so. cal. they were for webber carbs. us machinists just think different. we would rather burn the time and gain the experiance than throw dollars at it just because, even if it is not considered "cost effective". our payment is in self satisfaction from having made it work. thanks again for the info you guys are great and jd does make a fine product. great work.


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