Problems with horsepower?

Hey everybody, I just got a WR450 and I'm going to be doing some pretty serious mods to it. I don't have much experience with these bikes so what should I be aware of as I start making more power? Final target is mid to upper 60s, which parts of the engine/transmission can handle this kind of power and what specifically should be beefed up? Thanks!

An un-corked stock WR450 will make between 42-45hp.

Full exhaust, YZ cams and jetting will get you around 50+hp.

You will have to invest some serious $$ to get 60hp.

I'll have a little help in the power department from my friend named Garrett and his dad Honeywell :smirk:. 65hp is a conservative estimate. I just need to know how well these engines and transmissions hold up.

Never tubo'ed an engine, will you have to lower the compression a little to prevent a detonation induced meltdown? Water injection?

If you can keep the top end together, the next question is the bottom end and transmission. Looking at my FZ1 or an R1 it appears that the WR/YZ engine is similar to one cylinder sliced off of of an FZ1 or R1 engine.

They're close, but not really. The WR is a 5-valve head where the R1 is a 4-valve and the displacement of a single cylinder is different (450cc vs 250cc). I plan on keeping compression around 12ish so it's still snappy and I'll be converting it to FI and running E85 so detonation will be pretty well controlled.

Anybody have any ideas what parts fail around this power level I'm going for?

the trans internals should take that no problem as long as your not slamming the hell out of the gears during operation. shift assemblies will hold up fine. only thing i would honestly worry about on that engine is the top end. keeping that high of a compression ratio and running force induction is going to lead to issues. make sure you replace the cylinder studs with new ones right off the bat. i would honestly also suggest dropping that ratio down a bit but your bike your wallet.

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