carb jetting after ex port modification

narx

gefufn tjuner
Does anyone have some experience with jetting change after exhaust port modification (width, timing), did it make engine run richer or leaner? Is there any rule of thumb for that?
I widened and raised my ex port and now it seems engine runs a bit richer than before.
 
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Does anyone have some experience with jetting change after exhaust port modification (width, timing), did it make engine run richer or leaner? Is there any rule of thumb for that?
I widened and raised my ex port and now it seems engine runs a bit richer than before.

Did you check to see what color the spark plug is? (eg: dark, white, brownish color etc..) If it is a bit dark (and wet) then yes, it is running rich, i would start changing the main jet lower by one or two sizes. Try each size down while running the bike for a lil while (full open throttle) then check the spark plug each time until you see a golden brown color, that is what you want to see, reply back if there are any more questions or problems.
 
Thank you, but I know how to jet a carb, I was just curious if someone noticed the same effect.
No I didn't check the plug, and I gave up reading plugs by the color of the insulator nose a long time ago, especially on a tuned engine.
 
Thank you, but I know how to jet a carb, I was just curious if someone noticed the same effect.
No I didn't check the plug, and I gave up reading plugs by the color of the insulator nose a long time ago, especially on a tuned engine.

Well I don't understand your original question then, explain more clearly. If your asking if messing with the port timing, modifying, raising etc. effects the carburation (fuel flow) then yes, its possible. BTW spark plug reading is still effective to this day, no matter how tuned the engine is, so I ask, why would you say that? And yes, I have experienced what you are talking about and seen it.
 
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Yes I know it can affect carburation, but my question was did someone noticed that engine runs richer after riseing and widening the exhaust port. If there are many people who noticed that then we can say it's very likely to happen, right? :)

edit: Ok thanks for the answer. Plug reading by reading the color of the insulator nose is wrong because it greatly depends of the plug heat range, also you can have almost same color with very broad jet range. I've proven that to myself with my previous engine.
 
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Yes I know it can affect carburation, but my question was did someone noticed that engine runs richer after riseing and widening the exhaust port. If there are many people who noticed that then we can say it's very likely to happen, right? :)

edit: Ok thanks for the answer. Plug reading by reading the color of the insulator nose is wrong because it greatly depends of the plug heat range, also you can have almost same color with very broad jet range. I've proven that to myself with my previous engine.

Oh I know that, I understand what your saying there, but I also know you can get a correct plug reading (by full throttle) by running the bike open to its limit for a good while on a road etc. then taking the plug out and checking it, maybe its old school but it works, and maybe we just do certain things differently, also I have noticed that the engine can get a bit richer after doing a modification like that, most likely because it is starving for more power. But anyway I hope everything works out
 
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