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Why don't people race MX bikes in Enduro?

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I got to ride my buddy's WR250F today for the first time in some tight technical terrain and I realized that having a lighter bike is so key for the enduros I'll be doing this year. Currently I'm on a 260lb Aprilia RXV450 and although this bike is AWESOME is the medium to open trails, I think I want to get a really light bike for the tighter trails.

I started looking at the normal choices like the WR250, CRF250X, 250XCF-W, and such, and realized that the "motocross" bikes like the YZF250, CRF250, and KX250F are another 20-25lbs lighter.

First off, what makes them lighter? Are they missing things that I'm going to put on them anyway? I don't need lighting anyway.

Also, I know these MX style bikes have a closer transmision, but if I'm riding in enduros anyway, I won't need to go that fast, and I could just gear them down for the tighter stuff. The fastest I went today was 40 anyway, and that was on the single open stretch on the loop. On my 450, I never left 2nd gear, and only hit 3rd on the 250F. I was sooooo much less tired after a loop on the 250F that I feel like I need to go out and buy one for my enduro races and tigher stuff, and I'll keep the RXV for the stuff that's a little more open.

I see a TON of 2 strokes in enduros, but I'd like to stay with a 4 stroke for the torque, and it's better for the environment.

My most tempting bike that I'm looking at are either the KTM 250SXF at 216 lbs, or the Kawasaki KX250F at 204lbs. If a MX bike is a bad idea, then I really like the KTM 250XC or XC-W.

I'm still trying to figure out if a narrower transmission would be such a bad thing since I really would only use 3 gears or so anyway.

Thoughts?

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I know alot of guys who run mx bikes in enduros and harescrambles. They usually get the suspension worked on add some mods to make it more off-road oriented and re-gear it.

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Along with the narrower trans gearing, there is also the harsher suspension valving and springs, and "pipey-er" hit of the power caused by the lighter flywheel.

I have a friend of mine who took a YZ 426, added the WR lighting coil and flywheel, re-sprung and re-valved it for trail use, added a light and barkbusters and that's his woods bike-it does still hit harder than a WR, but is manageable, but he says after 50 miles of an enduro, it can get to be a handful, but he loves the lightness of it over my DRZ or any of his previous "woods" bikes.

Another friend of mine runs a CR250R (smoker) with a FWW and Rekluse and susp mods in the tight and nasty's out here (OR Mt's) and loves it.

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I couldn't decide if it was the power of the 450, or the weight that wears me out so fast. Obviously both have an effect on that, but that's a good point about the MX bikes having a harder "hit". I don't think that would really help anything in a long enduro. One of the reasons I want a 4 stroke is because of the wider, no surprises power.

I'm still hoping for some replies about the transmission being a closer ratio.

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the close transmission hasn't really been a factor for any of the guys I know. It really only makes a difference in the wide open sections. Like I said you can re-gear the bike for more speed but what you gain in overall speed you will sacrifice in bottom end power.

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It really depends on where you live and the local enduro rules. Lots of places, such as here in Ohio and most of the Northeast require lights and a license plate. If that is needed, it's easier to start with a WR, CRF-X, etc... that either have the lights already, or at least have the stator/wiring like a KTM XC. Even so, lots of guys around me do convert MX bikes for enduro use (especially Kawasaki and Suzuki fans). As to the weight differences between the MX and off-road version, it comes from the parts that make an off-road bike an off-road bike and not in the big parts like motor and frame. Well, I guess the Yamaha WRs are a year behind the YZs as far as the frame goes, but the point is that the weight is not do to inferior design that makes the off-road bike heavier. Also, the close ratio vs. wide ratio tranny is really a rider preference. My bike has the w.r. tranny and there are plenty of times where I think I would be better of having a c.r. tranny, then we hit a road transfer section where we have to cruise at 50 and the overdrive nature of 5th gear is nice.

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I couldn't decide if it was the power of the 450, or the weight that wears me out so fast. Obviously both have an effect on that, but that's a good point about the MX bikes having a harder "hit". I don't think that would really help anything in a long enduro. One of the reasons I want a 4 stroke is because of the wider, no surprises power.

I'm still hoping for some replies about the transmission being a closer ratio.

Need some homework first, does the governing body for the enduros you want to ride specify lights etc?

As for the wide ratio, first it's a match for the engine, a typical enduro engine has far more flexibility in it's rev range than an MX bike. That means you tend to (or I do anyway) select a gear which gets you the power you want for the traction you've got rather than peak HP all day long. Second, in some events you'll be faced with almost trials section bits, 1st gear needs to be low and the engine needs good tractable power at low revs. The few multi-enduro bike / multi rider tests I've seen that I can believe tend to show that 200 to 250cc 2 strokes are fastest, even when ridden by expert 450 4T pilots. The time will come when 300(ish)cc 4 strokes loose another few pounds and then that would be my choice (they're already close). For me the MX/Enduro decision is a no-brainer, yes an MX weight enduro bike would be great but not if it means sacrificing that flexibility... but that's just me :applause:

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I should say somewhere as well....

I could probably be convinced into a 2 stroke, however, my first bike was a 1985 CR250. I know bikes have come a long way since 85, but that bike had a huge hit when it hit the powerband. I would think that would be a nightmare in tight trails. Are the 2 strokes of today able to be lugged when you need to and not kill you when they hit the powerband?

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I should say somewhere as well....

I could probably be convinced into a 2 stroke, however, my first bike was a 1985 CR250. I know bikes have come a long way since 85, but that bike had a huge hit when it hit the powerband. I would think that would be a nightmare in tight trails. Are the 2 strokes of today able to be lugged when you need to and not kill you when they hit the powerband?

Test ride one of the new KTM's, 200 or 300 XC or XC-W, they lug like a thumper, yet act smoker-like on top-really wierd bike, I am quite impressed with them. Many call them a 3-stroke.

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Need some homework first, does the governing body for the enduros you want to ride specify lights etc?

As for the wide ratio, first it's a match for the engine, a typical enduro engine has far more flexibility in it's rev range than an MX bike. That means you tend to (or I do anyway) select a gear which gets you the power you want for the traction you've got rather than peak HP all day long. Second, in some events you'll be faced with almost trials section bits, 1st gear needs to be low and the engine needs good tractable power at low revs. The few multi-enduro bike / multi rider tests I've seen that I can believe tend to show that 200 to 250cc 2 strokes are fastest, even when ridden by expert 450 4T pilots. The time will come when 300(ish)cc 4 strokes loose another few pounds and then that would be my choice (they're already close). For me the MX/Enduro decision is a no-brainer, yes an MX weight enduro bike would be great but not if it means sacrificing that flexibility... but that's just me :applause:

+1.

If you can focus on a smaller mph "window" of speeds then wider gear spacing is not as important. Super low speed stuff + wide open running may not be as much fun on a mx type bike.

You rode a bike and noticed a difference in weight - when I ride different bikes the first thing I notice is the gear box. Its all in what works for you.

.

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MX bikes are lighter do to the absence of electric start, lights, and other bullshit they put on trail bikes---In woods, I would love to use an mx bike, but on long Baja type trails, I would want a heavier bike so it would be more planted. When I am on my mx bike, I will go into a burm 5th pinned, and it will feel as though the bike wants to fly away from me, so I have to keep it into the burm.

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Are the 2 strokes of today able to be lugged when you need to and not kill you when they hit the powerband?

well, 95% of all the top woods racers in the US ride 2-strokes, so what does that tell you. pretty much only lafferty and david pearson (and maybe caselli?) seem to be on 4-strokes. i'm sure there's a couple other guys that are either being paid specifically to ride 4-strokes, or race dezert or worcs where a 4-stroke is not such a disadvantage.

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well, 95% of all the top woods racers in the US ride 2-strokes, so what does that tell you. pretty much only lafferty and david pearson (and maybe caselli?) seem to be on 4-strokes. i'm sure there's a couple other guys that are either being paid specifically to ride 4-strokes, or race dezert or worcs where a 4-stroke is not such a disadvantage.

I appreciate the analogy, and it obviously is a good point. My concern though is that I'm no where NEAR as good a rider as anyone you mentioned. Maybe those guys are faster on 2 strokes, but are the bikes harder to handle because of the hit into the powerband? No I haven't gotten to ride one, but that's what I'm trying to figure out.

The KTM 300XC is tempting because people seem to call it a 3 stroke. However I know someone that switched from a 300XC to a CRF250 because he thought the 300 had too much torque. I'm trying to go to a tamer bike like a WR250F that weighs as little as possible.

Does the KTM200XC have a hit like a typical 2 stroke? I just want it to be easy to control like a 250F.

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I appreciate the analogy, and it obviously is a good point. My concern though is that I'm no where NEAR as good a rider as anyone you mentioned. Maybe those guys are faster on 2 strokes, but are the bikes harder to handle because of the hit into the powerband? No I haven't gotten to ride one, but that's what I'm trying to figure out.

The KTM 300XC is tempting because people seem to call it a 3 stroke. However I know someone that switched from a 300XC to a CRF250 because he thought the 300 had too much torque. I'm trying to go to a tamer bike like a WR250F that weighs as little as possible.

oh, ok. i get it. sorry i missed the main point of the question. here's what i think:

1. the ktm offroad models (xc and xc-w) are torquier smoother engines that most mx bikes, but even modern 250's from the japanese are pretty easy to ride because of the power valves. they don't act like a light switch anymore.

2. you're in colorado, so unless you're super super light, i wouldn't worry about a 300 having 'too much torque'.

3. i was still pretty much a beginner when i got my 300exc in 2002. it made me a better rider right away, and i think it's the easiest bike to ride really gnarly stuff on. if you're used to a wimpy bike (like my old klx300) it will seem pretty powerful at first, but it only takes a couple rides to get used to it if your body and hand position is right in the first place.

4. my girlfriend, 5'4" and 120 lbs, who has ridden for 2 years and was on a wr250f, just got a 250 xc-w 2-stroke. not only is she faster and falls less, but she feels like she has better control in more technical stuff. i think you would be shocked at how easy modern 2-strokes are to ride.

a kdx 200 or 220 is an even tamer and woodsier 2-stroke than the ktm's, but typically will require more modification for high performance riding.

from what i hear, those aprilias are not the easiest bikes to control, but that's just magazine blather. they sure do look purty.

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How to make a 2s better for the woods?

There are many posts on woods bikes which involving increasing the low power and reducing the hit. Look in your manual and see if your powervalve has an adjustment on it for more low end. Powervalve spacers are an option. A heavier flywheel and a pipe made for low-midrange also helps. Furthermore and lastly, 4s have 12:1 compression or so while A 2s is roughly 10:1 and therefore, next time a top end is needed you can opt for a taller piston to increase compression and increase low end power.

While most reeds claim they don't change the low end, fact is that it does and here is an good site to learn about how to 'really' mod your 2s for what you want:

http://tsrsoftware.com/redesign.htm

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Thanks for all the replies guys. I think you have me sold on a 2 stroke.

Now the debate is between... (KTM bikes)

1.) XC or XC-W... I'd rather not shift as much, and I think that means I need to get the W. Also, I know the suspension is softer on the W which is definitely what I want.

2.) 200 vs. 250 vs. 300... I'm coming off of a 450 4 stroke and until I rode my bike in the tight stuff though all I had to do was just not use the throttle as much and it wouldn't be any different. No I know the difference, and I really liked how tame the 250F I rode was. It felt like I could ride it all damn day and not get tired. Based on that...

-Do you think the 200 2 stroke will feel most simillar to a 250 4 stroke? I like the fact that the 200 is 6 lbs lighter than the 250/300. I think if I go larger than the 200, then I'd get teh 250. It looks like the only difference between the 250 and teh 300 is the bore, and if I wanted more power, I could just put a larger cylinder and piston on it during the first rebuild. Is it that easy to change?

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-Do you think the 200 2 stroke will feel most simillar to a 250 4 stroke? I like the fact that the 200 is 6 lbs lighter than the 250/300.

the 200 is the pipiest and hardest-hitting of the 200/250/300 bikes. i'd try to get a ride on one and see how you like it. i'd personally recommend the 250 unless you're pretty heavy, but all 3 are great bikes with subtle differences.

imho, the 250 and 300 feel alot like a 250cc 4-stroke in the low end and midrange, they just have alot more power up top when you need it.

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