Last summer (2013), after not riding since the late 1980s, I bought a 2012 WR450F to ride tight woods with my friend, an ex racer.
Its been an incredible journey. In the beginning I struggled on even the simplest trails. I now competently handle intermediate and advanced trails and I'm improving with every ride.
Part of my struggles were due to my bike selection. The WR450F, as shipped from the factory, is NOT an ideal tight woods mount. However, with some modifications it can be a very competitive mount. I now find myself keeping up with conservative 300cc 2 stroke riders on tight trails, without expending any more energy than they are. Part of this is due to vastly improved riding skills, but a great part of it is due to bike setup.
I bought a WR450F because 1) its not a motocross bike, 2) its very reliable 3) it has good suspension and 4) it has an outstanding engine. Its also pretty inexpensive, especially if you find a good used one.
I didn't buy a WR250F because in the long run it wouldn't have had enough power for me.
I think it was pure genius that Yamaha stuffed the 450 engine into the YZ250F chassis. The WR450F has all the right parts to be an outstanding tight woods bike. I'm not an expert or anything, but, here is what I have done (so far) to bring it up to its full potential.
The fuel injected WR450F weighs 260 pounds without fuel from the factory. This is way too heavy to be a good tight woods mount. I removed about 22 pounds from my bike as described in my weight loss thread. As far as I am concerned, the difference is night and day.
People argue for keeping the electric start. I don't get it. The EFI WR450F rarely stalls, especially once you get good at clutch modulation. And when it does stall it fires back up quickly and easily.
The thing about the weight loss is that its pretty inexpensive and its easy to do. And you can always add stuff back on the bike if you want to.
Two of the weight loss items have performance implications. 1) Exhaust. 2) Starter gear removal. The latter lets the engine spin faster and gives it a more responsive, revvy feel. It also reducing the spinning mass, making the bike feel lighter. This makes riding tight woods much faster and more fun.
A stock WR450F is geared way too high for true tight woods riding. My bike is presently geared 12/51, which I find to be pretty good. I do find I am revved out in 1st quite a bit lately. I might drop to 12/54 to make second more usable.
Gearing down obviously limits top end speed. Where I ride and who I ride with makes this a non issue. Its still way faster than the motocross based bikes.
Stock WR450Fs run pretty hot when idling or slipping the clutch or in slow high load conditions, ie mud or climbing a lot. They also run hot when lugging.
My WR450F was prone to boiling over last summer. I replaced the 1.1 bar rad cap with a 2.1 bar rad cap and haven't had any further problems. If I have further issues, I'll add an electric fan.
The stock MX51s leave a LOT to be desired in the woods. I'm currently running an 140 IRC M5B in the back and an IRC "Vulcan Enduro" VE350F in the front. I am not running a Tubliss. I am running stock tubes. I'm sure there are stickier tires, but the IRCs are reasonably priced, wear reasonably well and work in a variety of conditions.
Having said all that, I was surprised at how much of the knobs were wore off my M5Bs after riding in hard rock for a few rides.
The stock cable clutch pulls hard and is pretty vague.
I replaced mine with a Magura hydraulic unit, with the small 9.5mm master piston. It works great. Clutch force is reduced and its much more precise.
Some people like Rekluse clutches. I'm on the fence. Once you develop good clutch modulation skills and learn to pull it in when you should, I question the need for a Rekluse. I especially like how much control I have of engine braking, etc with a manual clutch over a Rekluse.
Aside: when I bought my WR450F, having never owned a 4 stroke, I was expecting never ending stump pulling torque that never stalled. The truth is that modern 4 strokes flame out more frequently and easily than the 2 strokes. This makes clutch management much more critical on a 4 stroke.
One big help in the flame out department is gearing. The faster the engine is turning the less its going to stall.
It takes a bit of skill, but once you get on to proper clutch work on a 4 stroke, stalling becomes a virtual rarity.
6) Suspension and geometry
The WR450F is a big bike and as such a lot of riders, like myself, are big. I'm 6' 1" about 220 pounds.
The stock 2012+ WR450F is probably sprung for a 180 pound rider. Soft suspension has 2 implications.
1) riders tend to turn up the damping in the fork to counter bottoming. This creates a harsh ride over rocks and roots.
2) When you put your weight back (sitting or climbing) the rear suspension compresses too far and it throws the steering geometry out, creating what I like to call the "chopper effect". The result is very vague and imprecise steering and the inability of the bike to follow rider input without constant, tiring, over correction. In woods riding, where the only good line may be 4 inches wide, this is a death knell.
If your 450F isn't steering well, try cranking up the preload on the rear shock. The difference was night and day on mine.
My bike is presently running a Racetech 6.0 Kg/mm in the back and 0.50 Kg/mm in the front with about 310 ccs of oil in the forks. This setup is not perfect, but it is livable and as good or better than most stock tight woods bikes.
My rear suspension is still too stiff over sharp bumps like roots, small drops and rocks. The front suspension is a bit too soft, though it is very compliant, especially over log crossings. The front end also feels pretty planted, though this is probably due as much too having the rear suspension set up properly as the front settings.
For the record, I have 21mm of static sag and 52 to to 58 mm of race sag in the forks. I have 12.5 mm of static sag and 98.5 mm of race sag in the shock. I realize I could decrease the preload in the rear a bit, but I love the precise steering that the current setup yields. I may drop the rear and raise the fork tubes in the triple clamps in the future.
The fork sag numbers tend to indicate the front is oversprung, and yet I say its soft. The problem is bottoming resistance. Racetech recommends 350ccs of oil for my setup to increase progression. I'll be adding oil to my forks in the future. If that doesn't give me enough, I'll update to 0.52 Kg/mm fork springs. FYI, the difference between 0.5 and 0.52 Kg for springs at half travel (150mm) is 6Kg or 13.2 pounds of force.
As far as clicker settings go, I'm running +1 on rebound front and rear, -2 on compression on the fork and I've backed high and low speed compression off dramatically on the rear.
Aside: I purchased my bike used from a guy my size. I checked the rear sag last summer and found it to be in the range of acceptable and thus rode it like that. What I didn't check was how much preload the shock spring had. When I removed the stock spring, I found it had about 40mm of preload ! Max allowable is 18mm. The spring had collapsed, which probably contributed to my handling/steering problems. FWIW, the Racetech spring is physically a much larger spring in diameter and overall length compared to the stock Yamaha spring.
One more thing about suspension: it makes a huge difference in woods riding. A day in the woods is no fun on a bike that bounces off every rock, log and root. A properly suspended woods bike is way, way faster than one that isn't, probably more so in the woods than on a motocross track. If there is one thing that will dramatically improve your enjoyment, its suspension.
The suspension on my bike is a work in progress. I'll update this thread as I discover more. I suspect the shock is going to need a Gold valve at some point.
7) Miscellaneous stuff
The stock seat on these bikes sucks as far as comfort goes. I'll be going with a tall, soft seat at some point.
I'm running the stock CO and competition ECM map. I'll be updating these as well. Don't even bother trying to ride a WR450F without the competition ECM.
I (6'1", in socks) find the stock WR450F ergonomics to be quite cramped. I reversed the foot peg mounts to drop the pegs about 3/4". That made the transition from sitting to standing a little less like doing squats. A taller seat would help too. I moved my bars to the full forward position by reversing the bar mounts. I wish these bikes had the top triple clamp from a YZ250F which has 2 holes in which to mount the bar mounts.
I cut my bars down to ~30 inches and added bush bars. They have rubbed many trees and saved many crashes !
I softened the rear brake response by introducing a bit of air into the master cylinder. Thanks for the tip, Krannie ! It works great. Prior to that the rear brake was too binary, ie on or off, especially on steep downhills. Now its much easier to drag it without skidding the rear wheel. I find the stock front brake to be very good, though sometimes I'd like a bit more braking power.
My bike runs way better on 94 octane fuel versus 91 octane. Its harder to stall and it has better throttle response. YMMV.
I've always liked my WR450F, but now I am beginning to really love it. The more I refine it the better it works. I absolutely love the engine. Power everywhere, totally controllable. I also love that the entire bike is 100% reliable.
I hope this helps someone trying to use a WR450F in tight woods.
Edited by MidlifeCrisisGuy, July 21, 2014 - 10:05 AM.