I know I'm probably jumping the gun here a bit, but I'm trying to gather some info on exhaust for the 450R. I know a few manufacturers have put out exhausts for the 450R. White Brothers has an exhaust which adds 3hp with the proper jetting and airflow. I haven't seen any exhausts that are designed for the 450R with the HRC kit. I know the HRC kit has a more open spark arrestor, but I think an aftermarket pipe would add additional HP as well.

Will the HRC kit require a different aftermarket exhaust and head pipe than the standard 450R for max performance?

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Max performance is a relative term. Sure a pipe would help, but by no means would it assure maximum performance. The power up kit is designed to give you confidence in a bolt on kit, designed, built, and backed by Honda, designed to give you more power safely. I would definitely get that kit if I had a 450R. Now a pipe, I would only consider if I was racing. Any performance pipe that you'd install on that 450R to make it any faster would rattle eardrums for miles around, and unless you are racing, the land closures you will face will not be worth the extra ponies you gained. But, like I said, racing is a different story.

Edit: I think I missed your question a little, which was does the HRC kit require a pipe. The answer is no, it does not require a pipe to be effective.

 

I may have phrased my question wrong. Part of the HRC kit is a spark arrestor that is more open. This was designed to go along with the HRC kit. Some of the pipe manufacturers are already making pipes for the stock 450R. I'm curious if an aftermarket exhaust would add any additional HP over the modified pipe (spark arrestor) with the HRC kit.

I'm having the HRC kit installed when I get the 450R, I wonder if changing out the HRC modified pipe for an aftermarket pipe would be worth it. Second problem is that the aftermarket pipes for the 450r are designed around a stock machine and not one with the HRC kit installed.

I was kind of hoping the following would occur. 450R stock 37HP, add HRC kit(13-15 % power increase) 42 HP,
maybe adding aftermarket pipe or full exhaust would add 1-2 more HP ??? 43-44HP

I know the HRC jet is a 185 main. You might be able to go 190-200 with the aftermarket pipe. I've seen the 450R dynoed with a .190 main, so this seems reasonable with the new HRC cam and needle.

The aftermarket header/exhaust may or may not allow for additional air flow and jetting and additional HP over the HRC modified stock exhaust. I hope this makes more sense. Thanks for the Info.

 

Yep it makes more sense. An aftermarket pipe will work fine, with or without the HRC kit. You'd very likely have to move up a size or two on the jetting if you went to a different pipe, but don't worry that the pipe was not designed for an HRC kit. Think of the guys that have aftermarket pipes on 440EX motors, they work very well. The biggest issue will be getting the correct jetting.

The 450R is in my future, probably next year. At that time, I will most likely run the HRC kit, with the spark arrestor, and live happily ever after.

 

The white brothers pipe that dynoed in Dirtwheels was setup with a .190 jet. The HRC kit comes with a .185, so it does sound like the new jet sizes will be .190 - .200. I am going to wait a few months and see how the aftermarket pipes perform.