Proper jet size for ported cylinder

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theguy2024

Member
Sep 25, 2022
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I have a 100cc/78.5cc Niome 2-stroke motor. Ported out intake/exhaust and installed one of those long flexible chrome exhausts.
My question how to properly Jet/adjust C-clip together for maximum performance. Tinkered with it a bit already Started going up and down with jet sizes and C-clip heights.

Is it just trial and error until It runs the best it can? I ended the night with an #88 jet and the leanest clip height and it was running really good! But I still think it could be better… Any input would be appreciated thnx
 

Larry Trotter

Well-Known Member
Nov 26, 2017
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If you think it can do better then fool with it a little more. If you are at the leanest position with an 88 jet go smaller and run the needle a notch or two higher.
 
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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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You have to be very careful when jetting 'by feel'... Too lean feels like a lot more power, but in reality you're burning up your engine!!!

I've learned to jet it bigger until you just feel a slight 'sputtery feeling' & then back it off a hair.
 
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Mossy

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May 20, 2022
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When tuning anything there's too much to or too little and 1/2 way between favoring on the just rich side ... Take your time between changes to feel the effect
 

Greg58

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May 1, 2011
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Where are you on the break in process? That determines what you need to do jet wise, if it’s a little rich and you’re still waiting on everything to seat in you might be better off waiting. Once the rings seat and the engine loosens up the compression and power will increase, I’ve found that a slightly rich engine during break in runs good after break in.