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350sxf compared to 250sx?

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How does the 350sxf compare to a 250sx? Which one is easier to ride on a motocross track? My 15yr old son has been racing a 250sx this year and he says it's just to much. He says it wears him out fighting it, I'm guessing it's the power ban of the 2 stroke. If you put him on a 125 or 250f he pretty much keeps them screaming around the track. He had a yz125 but at his size 6ft 2in 185lbs he tore it up constantly. So that leaves a 250f or maybe a 350f. I'm not sure the 250f would hold up any better than the 125 at his size riding it hard all the time. Does the 350sxf have any low end grunt like the 450f's do or do they have to be screamed all the time like the 250sxf does? Is the 350sxf easier to ride than the 250sx is?

 

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From what I have been able to find the 250sxf has 44 horsepower, 350sxf has 50 horsepower, 450 has 57 and a 250sx has 53 or 54 horses. So with the 4 stroke power delivery the 350sxf should be quite a bit easier on you than the 250sx is or am I wrong?

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I would say the 350 is the most similar whilst being easier to ride

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I sent you a PM but I have a 350 that you can try depending on what part of MO your in. 

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The 250 SXF is the one you want. IMO the 350 feels closer to the 450 handling and power wise. 15 is pretty young, plenty of time to move to bigger displacement bikes in the future and the smaller CC bikes will make him a better more aggressive rider. The 250F's these days have plenty of power. 185lbs isn't that heavy.

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On ‎4‎/‎29‎/‎2017 at 11:51 PM, SonsRexspensive said:

How does the 350sxf compare to a 250sx? Which one is easier to ride on a motocross track? My 15yr old son has been racing a 250sx this year and he says it's just to much. He says it wears him out fighting it, I'm guessing it's the power ban of the 2 stroke. If you put him on a 125 or 250f he pretty much keeps them screaming around the track. He had a yz125 but at his size 6ft 2in 185lbs he tore it up constantly. So that leaves a 250f or maybe a 350f. I'm not sure the 250f would hold up any better than the 125 at his size riding it hard all the time. Does the 350sxf have any low end grunt like the 450f's do or do they have to be screamed all the time like the 250sxf does? Is the 350sxf easier to ride than the 250sx is?

 

I had a 2011 250sx and currently ride a 2013 350sxf.


Whenever I jump back on a 250 2t, it always feels like 'too much' and that I'm fighting it. That usually lasts for about one or two track days with arm pump and fatigue, until I start to remember and relearn the skill it takes to control the 'narrow' and explosive power of the 250 2t. My point is that getting used to the 250 2stroke takes quite a while, even for an expert that has been riding 2strokes for most of his life. Also, ideally you'll be testing the 250sx on a sand or loam track and the jetting will be in the ballpark. If you test on hardpack with jetting that's too rich or too lean, you'll have a much harder time coming to terms with the 2t compared to an EFI 4t.

 

The power curve is much broader on the 350sxf and even as an expert rider, I am never short of power or grunt out of my 350. I guess I might feel a bit down on power if I jumped back and forth with a 450 or weighed more (currently weigh 155lb), but I can honestly say I am very happy at the moment.

 

 

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I would have to agree on the 250sx being a handful, they are very light and have such explosive power inside them. I personally can't confidently ride a 250 smoker on a moto track. But that's just me. 

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From what I have been able to find the 250sxf has 44 horsepower, 350sxf has 50 horsepower, 450 has 57 and a 250sx has 53 or 54 horses. So with the 4 stroke power delivery the 350sxf should be quite a bit easier on you than the 250sx is or am I wrong?


Think you got these mixed up. 250sx has 50 hp and the 350 has 54. All the mag shootouts I've read put the 350 as around the same peak hp as the 2016 CRF450. The 250 two strokes have always been around 48-50hp.

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They are all roughly within 10hp of each other , but the way they make the power varies hugely

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I own the smoker and happened to ride a 350 this weekend.  Yes the 350 would be easier to ride, as the power is much smoother.  However, it is heavier, and feels heavier.

I think you should explore MUCH cheaper solutions before changing bikes.  For example, simply swapping heads on the smoker will dramatically affect the power characteristics.  I run an XCW head on my SX for woods racing, as it makes the power much smoother and the bike is far less tiring to ride for a two hour race.  I paid $50 for the head on ebay.  It is a direct swap with no need to re-jet or anything.  The bike is still stupid fast, but the power is much easier to deal with, especially when you get tired.  

Even cheaper (free) than a head swap is playing around with the PV springs and preload.  The different springs really alter the ramp up of power, and even changing the preload on a given spring makes a noticeable difference.  

Then don't forget the time honored solutions of FWWs and throttle cam systems (about $100 each).  

I would try powervalve springs first (free!)  The try the head.  Go with the XCW head.  The XC head, depending on the year, will likely be similar to the SX head. 

Edited by rpt50
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My son races a YZ250F and he is 185 lbs. We just set the sag and suspension up for him other then a pipe its all stock and he flies on it. He rides it hard! and it holds up really good, very durable. We both went from RMZ450's to 250F's as a result are faster. I grew up riding 2 strokes and got rid of a 2016 KTM 250SX to go back to 4 strokes, the 2 stroke put a big smile on my face on the straights but got out of shape a lot on the jumps. A 125 2 stroke can't compare to the 250F's in reliability and maintenance thats been my experience. Since your son has ridden 4 strokse he knows the advantages.  

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I've ridden a 17 250sx and I own a 17 350 sxf. The 250sx is an awesome bike but I don't think it's the right bike for a 15 year old. The 350 has less snap off the bottom making it easier to ride, and has a very linear powerband. The 250sx is the easiest to ride 250 2t I've ridden but it's still a handful. I think the right bike for him is a 250 4T. It will be much easier to ride and with skill, he can go just as fast. The 350 is a great bike and it lets you be a little lazier than you can be on a 250 4T. Still you should be able to do basically everything on that 250 4T that you can do on a 350. At 15 and the fact that he's racing, he should still probably be developing corner speed. The 250 4T would be the better tool for that.

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