Posts
880
Joined
5/18/2017
Location
CA
Fantasy
592nd
I had a chance to ride a new TM 300 MX the other day, and was very impressed with the engine. It had abundant torque with a very linear pull and fantastic throttle response. At one point, I slowed right down and shifted up a few gears just to see if it would pull it and it did, with surprising ease. If it was my bike, I would just gear it a bit taller to stretch out each gear a bit and you could ride it like a 450 - a very light and zippy 450.
Then I went to my own bike to actually race - a 2016 250 sx - thinking "wow, that was fantastic, I think I need a 300 kit" and ended up feeling really torn about it. No, I don't have that low end grunt to the extent of the TM 300, but my engine felt playful and fun in comparison (if that makes any sense?). The only KTM 300 I've ridden was an xc, and that engine felt almost boring - the TM felt a bit more aggressive, like you'd expect from an mx engine while the xc felt rather tame. Is the 300 sx kit much different than the 300xc? I'd hate to put a 300 kit on my bike only to find it boring. If it felt that that TM 300 I'd be happy (which is probably a useless comparison for most people since most people will never have ridden one). If it felt like the 300 xc I think I'd be disappointed. I hope this makes some sense - it can be difficult to articulate just what you felt when riding, and what you'd like.
Then I went to my own bike to actually race - a 2016 250 sx - thinking "wow, that was fantastic, I think I need a 300 kit" and ended up feeling really torn about it. No, I don't have that low end grunt to the extent of the TM 300, but my engine felt playful and fun in comparison (if that makes any sense?). The only KTM 300 I've ridden was an xc, and that engine felt almost boring - the TM felt a bit more aggressive, like you'd expect from an mx engine while the xc felt rather tame. Is the 300 sx kit much different than the 300xc? I'd hate to put a 300 kit on my bike only to find it boring. If it felt that that TM 300 I'd be happy (which is probably a useless comparison for most people since most people will never have ridden one). If it felt like the 300 xc I think I'd be disappointed. I hope this makes some sense - it can be difficult to articulate just what you felt when riding, and what you'd like.
The Shop
I built a modified 2013 300sx and the torque was great. But I had it built for torque and it would rev out pretty good with the bills pipe and silencer. The vibration was KX500 level.
With my 2017, I have debated recently doing the 300 kit, PWK and STIC metering block just because, but I damn sure the minimal vibration of the 250 though.
Then, decided to go to the 327, which took the stroke from 72mm to 76mm. All necessary parts and pieces were sent to CrankWorks in Arizona to modify/balance the crank with the parts (piston/rod, etc.). Bike vibrated much less and had a more aggressive longer powerband. A bit more of a 250-esque hit in mid-range. Put a flywheel weight on it and relegated it to full off-road. A perfect bike for me off-road and reliable as well.
I’m pretty sure they prefer the EXC 300 jug on the 250SX. Tune from there.
They had some interesting results from different pipes on 300 conversions as well. - Where the power was focused.
If you're looking for a little more TM like delivery, it sounds like the SX would suit your needs. Anything can be de-tuned / smoothed out with a gearing change, flywheel weight, ignition timing, or power valve adjustment. The XC would be mellower from the get go.
Not sure if KTM still offers this same kit with ignition kit etc., but MXA did a comparo a few years ago.
https://motocrossactionmag.com/two-stroke-test-we-turn-our-ktm-250sx-in…
Cylinder: The 293cc cylinders are the same for the enduro (EXC-W), cross-country (XC) and motocross (SX) models, and they have had the same porting and specifications since 2009.
Cylinder head: There are two different cylinder heads; a slightly lower compression XC head and a high-compression SX head, which still runs on pump gas.
Piston: Like the cylinder, the flat-top pistons have been the same since 2009. Some tuners feel that the flat-top piston is better at controlling detonation and works much more efficiently with pump gas.
Black box: The XC and SX kits have different maps. The ignition for the SX kit is more aggressive (as you would expect).
TM changed the head, cylinder, and power valve assembly for the 300. Doesn't look like there's a different MX specific head for the 300MX, but each model on the TM has its own CDI. EN250/300 and MX250/300...so 4 different CDI's spec'd for each model exclusively.
Other differences look like internal and final drive gear ratio changes between the Off-road models and MX models.
Could have overlooked a part or two, but here's the source. http://tmracingmotorcycles.com/support/parts/.
Although I think he's called my bluff!!
Pit Row
That being said, I'm 5 foot 7 inches / 150lbs so I just don't need more power than the 250 delivers. My buddy who owns the big bore is 6ft 3 and built like a brick shit house. He loves the big bore.
So there you go.
p.s. We had a hell of a time getting that big bore dialed in. Ultimately the it was a timing issue.
At this point in my life, if I wanted "more" I would just buy a 450. I would want something that clearly has more everywhere. If its a two stroke, I still like the 250's.
Post a reply to: 250 vs 300 2 strokes