Bought a "used" 2024 yz450fx that only had 2.5 hours on it. I'm going to use it for my race bike and I'm keeping one of my 2019's for a practice/fun bike, so this one gets to be dedicated to the gnarly rocks we have in the flint hills.
I did the obvious and check the air filter, good to go! Next I changed the oil, it came out looking like it only had 2.5 hours on it, so that's good 👍. The next thing I installed was a rear brake return spring and clevis. I don't think it's 100% necessary, but it does take out some of the play and looks cool. While installing it I took the rear brake arm and sanded off the casting marks, then soda blasted it to look matte again. Also not necessary, but makes it look so much better to me. When I pull the linkage I'll remove the casting marks from it as well, but I'll ride 20-30 hours before greasing it and the swingarm.
I'm selling my old 2019 race bike to my brother who will ride in mostly clay and sand, so I'm removing the Dunlops and putting them on that bike. While the rear wheel was off I installed a chain guide and 2 link longer x-ring chain. I run the rear wheel back about 3/4 of an inch from most, it really helped on my 19 and I hear the is chassis would probably benefit from it more than the old one. To keep the axle alignment bolts from being out another 3/4 of an inch, I run aftermarket axle blocks. I will say the Yamaha OEM ones have stepped up on the alignment marks, and I almost just ran them. The reason I almost ran the OEM blocks is because the ones I had ordered from Nice CNC were too small. I didn't realize they upped the axle size on the newer gen fx's, but turns out I have a stepper but that was the perfect size.
For the rocks and roots I race in, I've been running the Tusk Recon front in 90/100R21 and rear in 120/100R18. I run 2-3mm tubes at 10psi front and 6-8psi rear. The larger tires allow you go air down more without pinch flats. I don't run bibs because I rarely get flats. Tubeless is just dumb, so I'm out on that.
One of my 2019's has a 14 tooth CSS, one has the stock 13. For now I'll run the 13, but I rode the 14 tooth bike in Moab and it's growing on me. Smooths out the power, but 1st is still good for rock gardens.
I still have front tires to mount, and my thermobob will get here tomorrow. I ride in the cold so I install a thermostat to make sure the engine stays above 180°. I don't know why these fuel injected bikes don't come with them, I guess people like gas in their engine oil...
This evening I'll also cut 1.5 inches per side of my handlebars off and thread them for screw in mounts. After that I'll ride it a bit before installing lighter springs. I'm 180lbs, but for the stuff we race in I run .42 fork springs and a 5.6 shock spring with 125mm of race sag. On the 19's I used stock valving, so I'm hopeful to be able to use it on the 24 as well. I opened the low speed and high speed all the way, and run 16ish clicks out on the rebound to allow the tires to follow the ground. Squishy is good for the woods!
Brake arm:
Ran into an issue with my 116 link chain. The swingarm axle slots are the same as the previous FX bikes, but the axle is larger, so it can't go as far back as the older smaller axle. So I got out my Dremel again and went to town. It works now!
Before I got the rear wheel back on I went ahead and put some anti-seize on the axle adjuster bolts.
I was planning on riding it before I did anything else, but the springs showed up before the new front tire, so I removed the shock to install a 5.6kg/mm spring. It's actually a softer spring than race tech recommended, but I run 125mm of sag, not 105. I'm actually glad I did the springs because the rear spring wasn't stock, it's a 6.4kg/mm.
So the previous owner bought this bike, paid to have springs put in it, frame guards, $180 hand guards, and rode it 2.5 hours 🤯. He also had a fan installed, but he or the dealership removed. I found one of the mounting clip nuts in the skip plate when I chanhed the oil. The fan connector was also missing the plug 😑. Cycle terminal got me covered though! I bought 2 plugs, one to make a sealed plug, and the other to change the 3 pin connector on the fan I have sitting on the shelf to the new 2 pin connector. The rest of the fan is exactly the same.
I'm not really worried about the fan because I never had an issue with overheating either of my other 450's. I might install it on my 19 because it's my fun ride bike and that's when these get hot is when you're going slow and stopping waiting for people a lot.
Another thing I found when pulling the fuel tank is the filter wasn't installed correctly. Glad I didn't go ride in the sandy trails like I was planning!
Another thing I like to do with all the plastic being off is to look at the frame and see where the rub points are. I then put some thin dense foam to help protect the frame. On previous bikes I was surprised at how deep some wear points can get over a couple hundred hours.
It actually lasts way longer than you'd think, and does a great job at protecting the aluminum.
Got the new front put on, a 90/100 fatty Tusk Recon to match the big 120/100r18 rear. I also got my thermobob installed. Bike is back together and just need to set sag and then move to the handlebars. Going to cut them down and install pillow top lock on grips.
The Shop
Free shipping: VITALMX
Handlebars cut down to 28 and 3/4 inches, pro taper pillow top lock on grips, Cycra ultra bar mounts moved all the way to the handlebar mount. I also installed a 1 piece handlebar mount. The small stock bar pad still fits, with modifications. Sag set to 125mm and it's ready to take out on some test rides!
Is there a specific reason for 125mm of sag?
I've always gone with 30% race sag for moto and 40% for woods. For desert style fast stuff or sand dunes I usually run 30%, but for anything 3 gear and under I like the 40% range. It helps the wheel follow the ground better when there's dips/holes because it has more drop travel available, and having the seat be an inch lower helps with my 31 inch inseam. Another reason is because I run lower spring rates for woods racing. To get to 30% sag with the 5.6 rear spring I would have a lot of preload.
First ride impression:
Took it to a friend's house that's just south of here. It's pretty flat, and the only rocks are man made ones. There are quite a few roots and logs to test the bump absorption on, and twisty tight trails to weave around.
Rider cockpit: I didn't really notice the lower pegs or narrowed frame. I didn't have any issues with the old one though. I felt right at home with it, but did notice the higher firmer seat. You feel more on top of this bike sitting down. Standing felt like a Yamaha, which I like. The round profile seat I don't really notice, but the foam feels a lot firmer that the old generation model. I'll have to ride it some more, but I may get a GUTs low soft seat.
New gen engine: it has a similar character, but definitely revs faster than the 2019-23 fx's. They say the clutch is over a pound lighter, so I'm assuming that's where most of the new feeling comes from. The clutch pull feels a little lighter, and modulation may be a little better than the old one. Personally I like cables, so not planning on switching to the hydraulic. I like the 5 speed Wide Ratio trans, I have experience with them going back to 2002, so I like this one. Throttle response in 1st when going slow can be a bit jerky, but every 4 stroke Yamaha I've had are light switches in this scenario, even the carbureted ones. I think a throttle cam that opened a bit slower could help this, but it's not an issue when riding fast.
Suspension: I'm running stock valving with light springs for my 125mm of race sag, 4.2 fork springs and a 5.6 rear. My compression clickers are all wide open, including the high speed, and rebound is 16 clicks out front and rear. This does a really good job for eating up trail trash, and I didn't experience any kicks or twitching bars. I got into 4th a few times to test for this head shake while braking I hear about on this chassis and can report that I didn't experience any today. My suspension settings being so much different than moto though may have something to do with it. Overall I'm happy going straight to my 40% sag and light springs. I don't think any re-valving is necessary, it did really well with just springs.
Overall ride: This chassis is easier to switch back and forth than the previous gen. One of the trails I was on today is a long zig zagging loop, so I got lots of testing on this aspect.
If anyone is on the previous generation and races in the woods I recommend upgrading. This is a good evolution of this bike, and squishy springs and long chain away from a solid woods racer!
Modified an older model right steel foot peg mount to work with the newer foot pegs. Trying to find someone who makes the newer ones in steel but so far all I can find is more aluminum ones, or really pricey titanium. So a $35ish stock one and broke out the Dremel again. I need to get the older style spring because this one is too long, and the up travel stop is now the brake arm mounting bolt.
Where do you order the thin dense foam from? Does it come with an adhesive backing? Brilliant!
I get it by the roll at Home Depot
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