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AFR affected by small dent in header ?

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As above I have got a small dent in the headpipe of my CRF250X, on the outside of the bend (just before the heat shield).

Bike seemed to be running a little different since, so I hooked up the wideband and it appears to be roughly 0.5 AFR leaner at idle and light throttle cruise than when I set it up 6 months ago.

The temps have risen since initial setup so its not related to that.

Could a small dent in the pipe do this ? I have seen much, much bigger dents in headpipes before.

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SHould have no effect, the dent is presumed to have an effect on airflow but AFR is a ratio of air & fuel and is created by the sipon effect as gas passes the atomizer in the carb, for example if air flow was reduced 5% then 5% less fuel would be siponed and AFR remain the same

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SHould have no effect, the dent is presumed to have an effect on airflow but AFR is a ratio of air & fuel and is created by the sipon effect as gas passes the atomizer in the carb, for example if air flow was reduced 5% then 5% less fuel would be siponed and AFR remain the same

I would have agreed with the above, however I have had to richen the fuel screw 1/2 a turn and raise the needle 1/2 clip to get back to my original settings.

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If it's pinched off good than you may be backing up more heat into the engine which may effect the fueling. If you have an IR thermometer see how hot the pipe is before/after the dent just for shts and grins.

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I have a 06 and I have the same dent. I tried the freezer trick 4 x and it did nothing. It doesnt seem to have any affect on performance. It seems to be only cosmetic for me!

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put the head pipe filled with water and put it in the freezer. It's suppose to work. When the water freezes it expands pushing the dent out. It might take a few cycles to get it out. Freeze thaw etc. It didnt work for me but thay say it works!

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do a search in general topic. search dent in header, or how to fix a dent . Any searches like this will give you all the info you need. it should take you to discussion about freezing the pipe. I just read about a bike like yours and it worked.

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