Why does my friend's WR have more power than my YZ

My buddy has an 01 WR (YZ specs). I've ridden this bike back to back with my 02 YZf and it definitely has more power throughout the whole range. He is running a White Bros R4 pipe, me a DR.D. Is this the difference or is it something in the jetting as some friends have suggested?

Perhaps its the WR's wide ratio transmition that feels different to you.

Everybody I ride with gives me crap because they think I'm always tweaking the jetting. I only mess with the carb if something has changed. In my opinion, if you have your jetting spot on, you will be able to notice a difference when you change something such as the number of discs in your aftermarket exhaust, or if there is a big temperature or altitude change.

What I'm getting at is jetting can make a huge difference in how your bike runs. I used to run an FMF Megamax and recently went back to a stock WR muffler with one of those new inserts. I had the bike jetted perfectly for the FMF but it ran like crap with the stock/insert. I adjusted the jetting to what you see in my signature and now it feels like I've got a whole new motorcycle. It runs better with the stock pipe than it ever did with the FMF. You need to get in there and get the jetting sorted out.

If the main is too rich, it will quit accelerating on top and you'll have to pump the throttle to go faster. Don't worry about going too lean because you'll know it if you do. If it's too lean on top, the bike will keep accelerating, but it will feel weak and rough as it does. Start with the main jet and do top speed runs. Then get the needle clip position sorted out. Too rich-bogging, too lean, weakness. If your bike starts and idles OK right now, your pilot circuit is probably OK. But you need to adjust the pilot circuit with the fuel screw by turning up the idle then adjusting the screw to where you get the highest idle, then turn the idle back down to where you want it.

I guarantee yours will run better than his WR after that.

Oh yeah: plug color tests are a waste of time unless you are some kind of expert, so don't worry about doing that.

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