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Only $10 for all 2026 SX, MX, and SMX series.
I saw in this video that Beta has an adjustable power valve.
5mm hex changes the spring tension on the PV.
Seems like a great idea.
Yes. Have done a 390, 430 and a 300, but all were race editions. Did not buy a 19 inch rear wheel.
Number plate
Race wiring kit
Little ods and ends.
First ride report: i’m a vet rider sitting about 200 pounds and I’m still awaiting my correct spring rates to show up, but I already can tell the bike handles very good corners better than my YZ 250 and it retains that light feel. The gear ratios felt similar to my YZ 250 but I was really impressed with the ability to lug third gear. I got pretty used to riding my YZ 250 on the pipe and mostly in the mid to top end range. I felt like the RX 300 doesn’t perform the best on the top end, but the mid range and bottom in pull were very strong. It certainly can be revved but the chassis felt much better when you ride it like a 450. By the way, the stock jetting recommendations in the manual are way too rich. In my opinion I kept things pretty rich, the first hour or so for break in but settled on a 42 pilot and 168 main (elevation 2000 ft). I had a trusted source recommend the N1EH needle and I likely will send the head off to get me dialed in for 91 pump. I’m racing the bike this weekend and the looks of the bike alone are enough for the win. This has been a dream bike for me and I’m very happy. Electric start is amazing btw! Haha
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Friend has a 21 300rx n 125 re converted to mx. Vs my 21 250sx yes it feels like it hits a wall up top stock. But 300's are more luggers then revver's. So ride it a gear high it will pull it.
Don't forget to play with the power valve spring setting. Also different springs can try.
Has tried the fmf fatty and silencer. Think tge stock hgs was better. Had that 2.1 looks more 4 stroke silencer. Looked like ass.
Bought a pro circuit setup thinking it would work. But it doesn't had it cut / modded to fit. Most of the issue is in the silencer to pipe area. So has a pc setup on it now. Actually looks nicer.
Check messico exhaust i thought they had one for the 300. Put one of thiers on the 125 and it looks a lot like a pro circuit setup. Small compact silencer. Dep might have something as well.
Boyesen rad valve on it now.
Suspension he went all out mx tech black jack inserts dlc coated tubes. Natty rear shock.
I would recommend the TM design swingarm slider with the lil frame protector. Chain gets too loose it will rub against the frame there.
Hated the stock seat it's really tall. Plus hard. He runs the stock RE seat. It's not as tall lil softer.
Other than just personal things done to it. Basic maintenance. It's been pretty rock solid. Only done 1 top end at 45 hrs and it didn't need it. 65 hrs now still on stock clutch.
The 125 is pretty fast too even in its enduro setup. Vs my 21 150sx it was hanging pretty good. Wish they'd make an RX 125 with a close ratio gearbox etc.
What a beautiful premix burning machine
Another follow up: about 8 hours on the RX now. Bike likes to be cornered but as SmokinJoe said the seat and bike in general are just tall. Just got a Guts standard foam seat but haven’t installed. I thought the stock seat foam was gonna be too stiff but I’m not really noticing it while riding. It would be nice to have a lower seat where one can sit into the bike a lil more.
First ride with fully revalved suspension. Felt good but not gonna lie, my track gets some hard chop and braking bumps and didn’t have the best comfort there. Kind of felt like just a really stiff frame feeling, slightly jarring. Did not feel it in my hands as much as I did through the rear.
Any engine Mount products out there worth looking at? Also do these things have a more broke in feel after a certain hour mark? Happy with the bike overall, it’s a learning experience.
Here she is, 350 2-stroke: https://www.betamotor.com/moto/rx-350-2t/
I have a confession to make: I miss my 2023 YZ 250.
The Beta is a phenomenal bike but I didn’t do myself or the bike any favors by switching mid race season and expecting it to be a fairly seamless transition. It’s been a learning curve adjusting to the power curve of a 300 after many many hours on a YZ 250. I got off to a rough start with my Beta about six weeks ago with a couple crashes, trouble balancing the suspension, and learning to trust the bike. It doesn’t do anything weird….very stable and turns well (those usually don’t go hand in hand). The power is very four stroke like and it feel much heavier and bigger than my YZ. I feel like I might as well have a four stroke honestly. The YZ is just a little more of a snappy two stroke experience which I’ve grown accustomed to. The Beta does many things well but I’m having a hard time adjusting. How’s everyone else doing with theirs?
The PV adjustment appears to be an exact copy of what the KTM's have had for many years. The adjuster screw is not a stopper or limit, it is a preload screw for the spring. The spring is providing resistance to the centrifugal actuator opening the PV. So, going more IN on the screw is more preload and delays the opening point of the PV to higher rpm's. You set the speed at which it opens (after it reaches the point it overcomes the preload) by changing the actual spring to a different rate. In the KTM's they are color coded red, yellow, green, etc. Here's a chart graphing the different springs and screw settings.
https://jdjetting.com/ktm-power-valve-springs-graphed/
Thanks! I went ahead and bought the 2025 Beta 300 RX last week and it should be delivered by end of this week. How are you doing by the way?
I just pulled the trigger on one... You got me nervous now. I was debating back and forth on the YZ250 vs the 300 RX for a long time. I guess we will see when I finally get to ride it. I am still waiting on delivery.
Probably because your YZ250 makes about 8 more hp then the 300RX. The 300RX makes less HP then any of the last Japanese 250 smokers and over 10hp less then KTM’s strongest 250SX motor from years past. For reference Dirt Rider’s dyno has the 300RX at 40.3hp and a YZ250 at 48.3hp. The new 350RX will likely be in the same HP range as the yz250 and 250sx. FWIW Dirt Rider’s dyno has a 24’ YZ250F at 39hp..
Have you considered a different exhaust? That might wake it up a little. I liked the Beta torque vs the YZ power delivery, but in the dry summer months you can really take advantage of the YZ power, so I understand where you are coming from.
Doing fine. Hope everything is good your way. Make sure you play with that PV setting. I feel many guys neglect it and ability it has to shape the power.
I'm confused. So the bike you guys are talking about that is 10hp down is this one recently tested by Vital?
https://www.vitalmx.com/forums/moto-related/review-beta-300-rx-two-stroke
In the test they say the 300RX was previously an enduro-based bike but that this new one is more MX-specific. While he says it goes flat on top I didn't get the impression it's 10hp down.
That 48.3hp number was from the 2023 model RX, the first year version. Each year after they made significant changes. 2024 also went from the 6 speed to a mx based 5 speed also. After 2023 it was making more power than the 250 2 strokes. The 350 will be even more.
48.3 is what a YZ250 makes, the 300RX was barely over 40. That is WAY down on power, that is stock 250F territory. Yes the 350 will make more but with the 300 being so down I’m pretty confident the 350 will only put up numbers comparable to a YZ250.
Pit Row
Yes, I’m running a Bills Pipes exhaust with stock silencer. My very first race on the Beta I hit something and destroyed the stock unit. Yea most of my tracks here in Montana are hard pack and the YZ did pretty good.
Could be but it doesn't feel like to me at least. Riding buds have KTM 300SXs and YZ250s. I'm on a '23 Beta 300RX and I love their KTM and YZ ( YZ250 is The GOAT MX Bike ) but they're not blowing me off the track by any means. I'd love to try a '25 300RX as it's mx focused compared to my '23. All these new bikes are just incredible IMO.
My pants dyno also didn't register an 8 hp difference.
Not after they changed cylinder spec, porting spec, ignition mapping, etc. it was an entirely new bike with way more power 2024 and 2025. 2023 was the only year it made as low of hp as you say.
I haven't ridden a yz250 since 2021 when i sold it for my yz450. I rode a 2024 RX300 and one of the first things i thought was that my yz250 had more top end. The 300 has good bottom and mid and then just goes flat. I did 2 laps on it and parked it
You are a year off, 2024 Beta 300 RX had six speed, I have one in the garage. 25’s are 5 speed.
I’m of the opinion the 24’s and up are up on HP. Mine’s was pretty dang salty coming off show room floor, way to salty for this old man. I swapped PV spring to green spring and installed the adjustment kit where you can adjust PV by hand. Even dumbed down it will still pull the front wheel when you don’t want it too in sunshine mode. I ride mine in rain mode most of the time.
One thing about the six speed 300 RX’s. Not much they want do, MX track, trails, single track whatever you want it will pretty much do.
Ya I fat fingered that my bad. I have a 24 300rx as well sitting next to a 2024 tx300.
Are you starting to gel with the Beta yet? The power valve setting is one turn in from the most agressive setting from the factory (most agressive is all the way out). You could try turning it in one or two or several turns to soften the bottom hit in exchange for more over-rev. There are 5 turns on the power valve and 3 big springs and 3 small springs available.. mix and match you have a lot of different power settings, and most all will trade lowend/ initial hit for more on the top, I believe.
Such a beautifully modded bike. Whose footpegs and rear brake pedal tip are you using? Is that an AS3 water pump cover? Do you find yourself fiddling with the hand-adjustable power valve much and do you notice a big change in the power characteristics?
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