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Hey all,

im shopping for my first two stroke. I’m a woods rider and I’ve found what looks like a great deal on an 250 sx. 

Changes in bike thus far are lower gearing on chain and softer spring on shock, bark busters and handlebar risers. 

I will certainly need an xc gas tank and probably work on forks. Anything else I can/should do to make this single track worthy?

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Tons of guys use the sx as a woods bike. Cheaper, lighter, faster. I would throw an acerbis big tank on it, I love the axp full coverage skid plate also. Besides that I think it comes down to preference. If it is a 17+ sx I would look into a keihen, lectron, or smartcarb. Those mikuni's can be a pain especially if you plan on riding at different altitudes.

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I bought a new 250SX for woods racing back in 09 when they were practically giving MX two strokes away.  I raced that bike very successfully, and while I saved money for sure over an XC, you still need to do quite a bit to get it right.  Here's what I remember:

1. Obviously MX suspension is going to pound you silly in the woods, so budget for a revalve and respring as needed.

2. Don't mess around with aftermarket oversize tanks like I tried.  Waste of money.  I finally bought an XC tank which was much better!  It costs more than aftermarket tanks, but the quality and fit is so much better.  

3. I found the motor far too much for eastern woods, and the map switch didn't seem to do anything that you would notice in the woods.  The best thing I found to tame the motor was one of those throttle cam systems (use the slow cam).  That really makes it much more manageable in the woods.  I also bought a FWW which didn't seem to help much.  You can also purchase an XCW head for peanuts (since everybody wants an SX head).  In some conditions (mud), the low compression head helps a lot, but I only used it occasionally.  

4. I eventually went to an 18" rear wheel.  These days you can buy a nice Tusk rim and spoke kit for $127.  I highly recommend that!

Suspension would be my immediate concern, but once that is taken care of you should have a very good base to build on.  

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Get the xc cdi so it revs slower, its much better and feels stronger then the sx. It just wont rev quickly. I raced mx bikes in harescrambles for years, its fine as is. A 4 stroke mx bike isnt the best for off road but a 2 stroke is a 2 stroke. If you need it mellowed out REALLY bad, get your ports changed. I have a 2014 te300 i took all the do-dads off, even kick starter. You just dont need that stuff on a 2 stroke to competitively race them in off road. Buy some tires and a revalve and send it.

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8 hours ago, rpt50 said:

I bought a new 250SX for woods racing back in 09 when they were practically giving MX two strokes away.  I raced that bike very successfully, and while I saved money for sure over an XC, you still need to do quite a bit to get it right.  Here's what I remember:

1. Obviously MX suspension is going to pound you silly in the woods, so budget for a revalve and respring as needed.

2. Don't mess around with aftermarket oversize tanks like I tried.  Waste of money.  I finally bought an XC tank which was much better!  It costs more than aftermarket tanks, but the quality and fit is so much better.  

3. I found the motor far too much for eastern woods, and the map switch didn't seem to do anything that you would notice in the woods.  The best thing I found to tame the motor was one of those throttle cam systems (use the slow cam).  That really makes it much more manageable in the woods.  I also bought a FWW which didn't seem to help much.  You can also purchase an XCW head for peanuts (since everybody wants an SX head).  In some conditions (mud), the low compression head helps a lot, but I only used it occasionally.  

4. I eventually went to an 18" rear wheel.  These days you can buy a nice Tusk rim and spoke kit for $127.  I highly recommend that!

Suspension would be my immediate concern, but once that is taken care of you should have a very good base to build on.  

The green spring makes a huge difference

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4 hours ago, mog said:

The green spring makes a huge difference

I would use the green spring in mud when the revs are low.  But otherwise I found it very hard to ride as it just delayed the hit, and then BAM it came on too strong.  

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2 minutes ago, rpt50 said:

I would use the green spring in mud when the revs are low.  But otherwise I found it very hard to ride as it just delayed the hit, and then BAM it came on too strong.  

Tweak it with adjuster and it never hits 

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On 5/6/2020 at 2:40 PM, andrewfrankl said:

Tons of guys use the sx as a woods bike. Cheaper, lighter, faster. I would throw an acerbis big tank on it, I love the axp full coverage skid plate also. Besides that I think it comes down to preference. If it is a 17+ sx I would look into a keihen, lectron, or smartcarb. Those mikuni's can be a pain especially if you plan on riding at different altitudes.

Good suggestion on the tank.  I mentioned in my post to just go ahead and go OEM on the tank, as I have had problems with both Clark and IMS tanks. However, I just picked up a Acerbis tank for my YZ.  It did have a little leak, easily fixed with a thicker O-ring, but yea, it's a really nice tank!! Great fit and finish.  I like it a lot, and it's probably going to be cheaper than KTM OEM.  

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5 hours ago, rpt50 said:

Good suggestion on the tank.  I mentioned in my post to just go ahead and go OEM on the tank, as I have had problems with both Clark and IMS tanks. However, I just picked up a Acerbis tank for my YZ.  It did have a little leak, easily fixed with a thicker O-ring, but yea, it's a really nice tank!! Great fit and finish.  I like it a lot, and it's probably going to be cheaper than KTM OEM.  

surprised you have had problems with the acerbis, myself and several friends haven't had any issues. My only preference is that the acerbis are a little bigger that oem xc, not hugely different but a good half hour or so of gas

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On 5/8/2020 at 6:01 AM, RacingDVD said:

My SX stalls faster then my EXC. Flywheel maybe?

The exc flywheel has teeth on it for the starter and is surely heavier, not to mention the drag the old starter system had on the engine itself. I removed the starter and hardwear/electrical from my 2014 and it feels free compared to when it was on. I was thinking of getting an sx flywheel for my te.....trade?

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Been on the classifieds and its easy to see that the xc, xcw, tx, and te bikes are extremely hard to find used.  The sx and tc bikes are dime a dozen and cheap too.  Of course its likely that the bike has been raced and ridden hard but if its a newer bike is seems like it could be a good way to go.  Four stroke xcf, xcfw, fx, fe, are all over the place for sale.  I just bought a fx350, new from '19 and while I love it I feel like I am missing something the 2t has to offer in tight woods.  

I put a FWW, throttle tamer, ECU remap for flame out reduction, and changed to front sprocket to 13t from 14t.  these things have gone a long way into making the bike a little more tame and more tight track worthy but I can't help watch the 2t people lug their 300s around anything and not stall.

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I had a completely converted a 2014 450 sxf into an xcf.  I even had the factory xcf frame with the kickstand mount built in (long story involving an insurance claim).  I had the stock xc gas tank, an 18" rear, every guard you can imagine, stock suspension with the kitchen sink thrown at it, power parts fan kit, rekluse exp 3.0, ktm orange powder coated frame, fmf carbon/titanium pipe with S/A, every part you could have on the bike except a steering dampener... and when i went to sell it.  I couldn't get close to as much as what stock xcf or xcfws were going for.  I got $4000 for that bike (aka what a stock 450sx was worth) after sitting on it for six months holding out for more money and at that point I was just glad to have it gone. 

My point being is you may get it cheap now but you're going to have to spend a bunch to mod it to suit your riding then when you go to sell it, its still just an SX and no one will want it.  Buy the xc or the xcw and get the bike you really want and also happens to be the one that will be easier to sell once you decide to move on. 

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4 hours ago, Bizzidy said:

Been on the classifieds and its easy to see that the xc, xcw, tx, and te bikes are extremely hard to find used.  The sx and tc bikes are dime a dozen and cheap too.  Of course its likely that the bike has been raced and ridden hard but if its a newer bike is seems like it could be a good way to go.  Four stroke xcf, xcfw, fx, fe, are all over the place for sale.  I just bought a fx350, new from '19 and while I love it I feel like I am missing something the 2t has to offer in tight woods.  

I put a FWW, throttle tamer, ECU remap for flame out reduction, and changed to front sprocket to 13t from 14t.  these things have gone a long way into making the bike a little more tame and more tight track worthy but I can't help watch the 2t people lug their 300s around anything and not stall.

Still grip and rip like a 450 when you find a place too.

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I have a 250sx that I like for singletrack riding. I've had other XCs and also Yamaha 2 strokes, all used for rocky, technical singletrack. I think you can get away with minimal mods, or get carried away with lots. It really depends on what you want - for some riders the SX would be fine stock. Others will want a few guards, a bigger tank, and an 18" rear. Others will insist on a kickstand, Rekluse, steering stabilizer, etc. IMHO - go ride it a lot and choose mods thoughtfully, instead of spending a ton of money on things the forums tell you that you "need."

I suspect the SX 2 strokes will become more popular for trail riding now that the XCs and XCWs are getting so complex and expensive.

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