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Problem with after market pipes (slip ons)


New Member

hopefully someone can advise...I own a 2007 Road King Custom, I have tried to make it louder than standard by adding "Thunderheader" slip on's a SE Race fueller and SE Hi flow air cleaner. All this is great as getting heaps more power especially top end but a lot of low end a de-acceleration backfire. I am assuming the pipes are not set up correctly and not sure if they can be, but seems to be running "hot" and possibly a bit lean. I have had the bike dyno'd at my local dealer to try and correct but not much joy so far.

If anyone can advise a possible solution i.e. different slip-ons etc it would be fantastic as we are coming over to the US for a 2 month trip (Sturgis etc with our bikes in a couple of months and it would be great to get this sorted.


For the most part any time you reduce the back pressure by changing the pipes, you will get some decel popping from them. Check the exhaust gaskets at the cylinder end of the pipes and at the joints for leaks which makes the popping worse. Hold your hands tightly over the end of the pipes with gloves on while it is running. If there are leaks in the system, you will hear a hissing and then do what is necessary to correct them. You should be able to stall the engine doing this too.
Can you post your dyno sheet with the afr? I found the SERF somewhat difficult to tune because the pots are
so sensitive. Also the pot adjustments bleed into the next rpm range. After about 15 dyno runs the power and
torque are good but the afr line is not perfectly flat. The bike does run perfectly with no pops or farts on deceleration.