Okay, here’s my blog post about boosting the horsepower on my XR400:
Alright, so I’ve been tinkering with my trusty XR400 for a while now, and I finally decided to really dive in and see what kind of power I could squeeze out of it. It’s a great bike stock, but who doesn’t want a little extra oomph, right?
The Starting Point
My XR400 was pretty much bone stock when I started. It ran great, don’t get me wrong, but I knew there was more potential hiding in there. I’m no professional mechanic, just a guy who likes to get his hands dirty, I did some research.
The Process – Getting My Hands Dirty
- First up, the air filter.I pulled out that old, clogged-up thing and popped in a high-flow K&N filter. Figured that would help the engine breathe a little easier.
- Next, the exhaust.That stock muffler is pretty restrictive. I ended up grabbing a used FMF Powercore 4 slip-on. Bolted that thing on, and man, it sounded meaner already!
- Jetting, jetting, jetting.This was the tricky part. I knew I needed to re-jet the carburetor to match the increased airflow. I did a lot of reading on forums, I ended up getting a jet kit and following the instructions. Lots of trial and error, taking the carb apart, swapping jets, putting it back together, and test riding. It’s a pain, but super important.
- I also fiddled with the airbox. Some guys cut bigger holes in the airbox lid, I experimented.
Feeling the Power!
After all that work, I finally got it dialed in. The difference was night and day! It pulled way harder through the entire rev range. It felt like a whole new bike! I’m not sure exactly how much horsepower I gained, I need to get it on a dyno someday, but it’s definitely a noticeable improvement.
My Two Cents
If you’re thinking about modding your XR400, I say go for it! Just be prepared to spend some time tinkering, especially with the jetting. It’s a rewarding feeling to get it all dialed in and feel the extra power. It’s not rocket science, but it takes patience. Have fun with it!
