Family Plan - what about the GIRL?

[WildMax]

Ok, adding motor bikes to the fleet of snowmobiles. Our type of riding will probably be aggressive trail and off road - no motocross racing though. I'm very familiar with mechanics and engines and can fix or modify anything. I wanted to stay with 4 strokes. My situation is getting enough bikes for everybody.

So far I've picked up a YZ250F and a WR250. I figure my son (210#, 6' 4") and I (175#, 6' 0") could ride these. One daughter is content with the four wheeler, my wife likes her horse, another kid already has an older bike BUT my youngest GIRL is my dilema - she is 16, 135#, 5' 4" and about as tough as they come (can pretty well take out most boys if they have it coming). She's not intimidated by speed and rides a mean 150hp sled at speeds over 100mph through forest roads (not wide open lakes). She doesn't have to be in front but she wants to keep up with the leaders.

She seems too small for the 250 four strokes - or the 39" seat. A 33-34" seat is about right. I think the 125 four strokes would seem lame to her. A local dealer had her on a TTR 230 which was ok height wise but maybe too heavy and another dealer suggested she go with a YZ85 so she could keep up with us and ride her aggressive style.

Any thoughts? I'm new at these bikes so suggestions are appreciated. Thanks.

 

[TimberPig]

For her, a KX 100 is going to be hard to beat. A little shorter than a full size bike, but plenty of power, light weight, good suspension, and it has larger wheels than an 85 (19/16 instead of 17/14).

 

[Masterphil]

Is she still growing? Maybe lower the suspension on a 250f?
A KX100 does sound like a good choice, but will be very different (faster) from the sleds she's used to riding.

 

[NM_KDX200]

I bought my daughter a TTR125LE, but she's total opposite of yours. Mine is fairly non-agressive.

I'm 5' 6" myself and my KX125 is a GREAT fit. I'd suggest something like that with a flywheel weight. You can find great used 125's for nice prices right now. Or consider a KTM200 and lower it with spacers in the suspension. I came SO close to buying a 200SX that had been lowered 2" but I had just bought my KX125 and decided to run it for a year. The KX100 would be a good suggestion, but I'd just go with a 125, myself.

 

[nikki]

I'm about her size, a little shorter - 5'5", 130 lbs., and have been riding 250F's since 2002. Of course I started on 80's, but quickly moved to a big bike after a few months on the 80's.

I would say, have her try out the 250F, and see what she thinks. At 5'7", she should be able to touch on her toes, on both sides of the bike. Since I'm 5'5", I usually shave about 1" of seat foam to make my bikes a little more comfortable, plus set the bikes' sag for my weight.

A 125 isn't any shorter than a 250F. It is a few pounds lighter, but harder for a beginner to ride, because you have to use a lot more clutch and shift and the power is more like a light switch, compared to the 250F which is smoother, and more like a tractor.

The KX100 is a blast, but at 5'5", I'm very cramped on a KX100 - feel like my knees are hanging over the front of the bike and hitting the bars. Plus you don't have as much suspension as you would on a full size bike.

Not sure what type of riding you all are planning on doing, but the TTR 230 is a heavy pig. I would not recommend that for a smaller female rider.
:ride:

 

[WildMax]

Thanks for the response. She actually is 5' 4" I found out so I changed my first post. On my 250F, her feet (flat) are 5" off the ground. Toes don't touch.

 

[WildMax]

...A KX100 does sound like a good choice, but will be very different (faster) from the sleds she's used to riding.

A KX100 will do over 100mph??? That's impressive.

 

[TimberPig]

A KX100 will do over 100mph??? That's impressive.

No, it won't be that fast, but the power to weight ratio and snappiness is a lot higher than on a sled. When you crack it on a bike, the power hits a lot harder and snappier.

 

[FruDaddy]

KX100 is probably the way to go. I don't foresee you finding a thumper that will fit her and pack the kind of power that you seem to be looking for.

And most of the world doesn't understand the difference between fast and quick, that 100 will be quick (30-35hp and 150 lbs). It geared correctly, I would estimate 55-65mph. I couldn't find an actual hp number, but the KX85 is 28.5.
The WR250 was only 15hp in 04 (same bore, stroke, and compression as 02), and at 224lbs, will probably be left behind by the KX.

source:bikez.com

 

[dirt bike dave]

I vote for KDX200 for starters. Comes with soft springs. Get it lowered if you have to.

 

[Masterphil]

No, it won't be that fast, but the power to weight ratio and snappiness is a lot higher than on a sled. When you crack it on a bike, the power hits a lot harder and snappier.

That, and sleds have a CVT wheras the bike has a 6spd and a manual clutch. It's not just a pin-it and pray like it is with a sled.

Two wheels, a touchy throttle, and a manual clutch just has a way with humbling even the most ego-driven jackasses, not that I'm implying that you are one.

 

[adam728]

And most of the world doesn't understand the difference between fast and quick, that 100 will be quick (30-35hp and 150 lbs). It geared correctly, I would estimate 55-65mph. I couldn't find an actual hp number, but the KX85 is 28.5.
The WR250 was only 15hp in 04 (same bore, stroke, and compression as 02), and at 224lbs, will probably be left behind by the KX.

source:bikez.com

Wow, is that some horrible mis-information. If you actually believe a WR250 is only 15 hp, even corked up from the factory, well...
And a KX 80 might get 28.5 hp at the crank, but not to the rear tire.

I'm not sure where people are figuring a 100 will be faster than a sled though. I spent a few years wrenching on both and doing a small amount of racing, and sleds just flat out haul.

I vote for a KX100 for her. I think she could fit a 125 or 250F, but would probably be more comfortable on the 100.

 

[TimberPig]

That, and sleds have a CVT wheras the bike has a 6spd and a manual clutch. It's not just a pin-it and pray like it is with a sled.

Two wheels, a touchy throttle, and a manual clutch just has a way with humbling even the most ego-driven jackasses, not that I'm implying that you are one.

Yes, the drivetrain efficiency is lower and drivetrain losses in a sled are much higher. The manual clutch and transmission is a big part of why bikes respond much quicker. Sleds are push the throttle and go, although to truly ride a sled, does take skill, the effort to making it go is so simple a monkey could handle it.

 

[TimberPig]

Wow, is that some horrible mis-information. If you actually believe a WR250 is only 15 hp, even corked up from the factory, well...
And a KX 80 might get 28.5 hp at the crank, but not to the rear tire.

I'm not sure where people are figuring a 100 will be faster than a sled though. I spent a few years wrenching on both and doing a small amount of racing, and sleds just flat out haul.

I vote for a KX100 for her. I think she could fit a 125 or 250F, but would probably be more comfortable on the 100.

In outright speed, a sled will be faster, mostly due to the ability of the CVT drive system to gear the sled higher than the bike. The actual hit and response of a bike is normally much faster and harder than most sleds, as the drivetrain doesn't cushion the reponse like abelt driven clutch does.

 

[adam728]

In outright speed, a sled will be faster, mostly due to the ability of the CVT drive system to gear the sled higher than the bike. The actual hit and response of a bike is normally much faster and harder than most sleds, as the drivetrain doesn't cushion the reponse like abelt driven clutch does.

Well earlier you said that the power to weight ratio of the bike was much greater than a sled, and that's just not right. Snappier, yes, faster, heck no!

 

[MXGirl230]

She should be fine on a 250 four stroke. Set the sag for her and it should be good. She will definitely feel cramped on a KX100, I'm shorter and a little lighter than Nikki and felt cramped when I rode one. You could always have softer springs put in and remember to set the sag and she should be good.

 

[nikki]

Another "shorten my ride" tip is sliding the forks up in the triple clamp. Of course you can only go so far, before you hit the bars. And you might experience a little unstability/headshake in the front end if you lower the clamp too much, but it will give you another 1/2"

Every bit counts! Shaved seat foam, raised forks/lowered clamp, shorter bars, 4" of sag....

But if she's really 5" from touching her toes (in MX boots) to the ground on a 250F, maybe a KX100 would be a good option, at least for starting out. At 5'5"/130 lbs., I could darn near touch flat footed on my YZ250F, with stock springs.

 

[TimberPig]

Well earlier you said that the power to weight ratio of the bike was much greater than a sled, and that's just not right. Snappier, yes, faster, heck no!

Faster is a function of gearing, not power output. If a bike was able to overdrive the gear ratio like a sled can, without loosing all bottom end, then yes it could easily walk away from the sled in top end speed. Since there are limitations to the size of the transmission case of a bike, we don't have as wide of a gear range to work with. In order to maintain bottom end power and slow speed riding capabilities, we gear them down. For desert racing, where they mostly run wide open, through the use of wide ratio transmissions and high final drive gearing, the speeds capable are much higher. For most other riding, absolute maximum speed isn't as much use, but being able to use the gears that you have available is. If I want to go 150 mph, I'll go buy a crotch rocket and kill myself on the highway. Dirtbikes rarely have a need to go that fast. Sleds really don't either, and in many situations, they are set up so they can't go that fast either.

 

[FruDaddy]

Wow, is that some horrible mis-information. If you actually believe a WR250 is only 15 hp, even corked up from the factory, well...
And a KX 80 might get 28.5 hp at the crank, but not to the rear tire.

I'm not sure where people are figuring a 100 will be faster than a sled though. I spent a few years wrenching on both and doing a small amount of racing, and sleds just flat out haul.

I vote for a KX100 for her. I think she could fit a 125 or 250F, but would probably be more comfortable on the 100.

Would you call it all "horrible mis-information" or just the hp of the WR. Please note that I did provide my source. This is because, while they are usually accurate, the number did seem a little low to me. It is listed as 15.2hp@7500rpm ans 15.9ft.lbs@6000rpm.
RWHP is affected by the final drive gearing, which can be changed within 10 minutes, so it makes no sense to use it for comparison. My son's 17hp KX65 pulls a lot harder since I dropped a tooth on the front. The motor makes the same power, but the torque multiplication in the final drive has changed the power delivered to the rear wheel. Geared correctly, you could get full engine torque to the rear wheel.

 

[SpeedyManiac]

I'd vote KX100. The bike is light, easy to start (nice for beginners), has quality components (suspension, brakes) and is low enough that she can touch the ground while still having lots of power. The KX also makes enough power that she'll have plenty of fun and can keep up with the bigger bikes. There's also lots of aftermarket support.

You could lower the suspension on a 250F but it will still be heavy and fairly hard to start.

Didn't Service Honda stuff a CRF250 engine in a CR80 chassis?

As for the sled remarks, when I took my cousin's RMK600 for a spin, it definitely had POWER. I had a real tough time hanging on when a cracked the throttle in wide open spaces. A bike does tend to hit a little harder with the shorter wheelbase that can cause a loop out, but if she can ride a big sled well I doubt she'll have a tough time trying out two wheels.

 

[adam728]

Would you call it all "horrible mis-information" or just the hp of the WR. Please note that I did provide my source. This is because, while they are usually accurate, the number did seem a little low to me. It is listed as 15.2hp@7500rpm ans 15.9ft.lbs@6000rpm.

That number is way low, about 1/2 what a WR would make at the rear wheel. What's really funny is that 15.9 ft-lbs @ 6000 rpm calculates to 18.2 hp. Of course, that site also says it has an automatic gearbox too. :laugh:

RWHP is affected by the final drive gearing, which can be changed within 10 minutes, so it makes no sense to use it for comparison. My son's 17hp KX65 pulls a lot harder since I dropped a tooth on the front. The motor makes the same power, but the torque multiplication in the final drive has changed the power delivered to the rear wheel. Geared correctly, you could get full engine torque to the rear wheel.

I assumed we were talking about properly geared bikes. And (as far as I know) dyno runs are corrected to account for the gear ratio between the engine and the rear tire, because you want a 1:1 ratio to get the proper numbers, but that is usually impossible to accomplish, so it's done by math.

I just made the comment about mis-information earlier because I thought it was pretty obvious that an 85cc two stroke shouldn't have nearly double the power of a modern day 250 4 stroke.

 

[WildMax]

Another "shorten my ride" tip is sliding the forks up in the triple clamp. Of course you can only go so far, before you hit the bars. And you might experience a little unstability/headshake in the front end if you lower the clamp too much, but it will give you another 1/2"

Every bit counts! Shaved seat foam, raised forks/lowered clamp, shorter bars, 4" of sag....

But if she's really 5" from touching her toes (in MX boots) to the ground on a 250F, maybe a KX100 would be a good option, at least for starting out. At 5'5"/130 lbs., I could darn near touch flat footed on my YZ250F, with stock springs.

Thank you for the great information!!!
She is 1" shorter than you and cannot touch the ground on tip toes on my YZ250f. I was thinking maybe getting her started on a TTR125 or KLX125 then moving her up to the 250f with a lowered set up. The only reason I was thinking 4 stroke was for the fuel range where we ride - however I see they can be a real pain to start.

 

[WildMax]

Yes, the drivetrain efficiency is lower and drivetrain losses in a sled are much higher. The manual clutch and transmission is a big part of why bikes respond much quicker. Sleds are push the throttle and go, although to truly ride a sled, does take skill, the effort to making it go is so simple a monkey could handle it.

Yes, on a sled all she has to do is squeeze the throttle. Now, she has to learn the fine art of shifting.

I'm guessing we have more drivetrain adjustment options on sleds - in addition to gearcase sprockets there's numerous possibilities with clutch tuning on two clutches and also drive sprockets.

Didn't Polaris use a similar CVT on ATVs whereas a lot of the others used transmissions like a bike?

 

[adam728]

Didn't Polaris use a similar CVT on ATVs whereas a lot of the others used transmissions like a bike?

Yup. Some people love it (easy to operate), some people hate it (like stated before, lacks the "snap" of a normal manual transmission). Biggest problem with CVT in a quad is keeping water and gunk out. That, and getting people to use low range when it is needed (I've seen dozens of destroyed belts and even a few melted clutch covers from people doing things like skidding logs in high range at WOT).

Polaris still uses CVT on the majority of it's 4 wheelers. Some cars now days are even coming with it as an option!

 

[kawicam125]

the kx 100 would be a good bike to begin on for your daughter. my brother has a modded kx 85 that flies. the kx 100 ( or so ive heard) are pretty much the same in power delivery as an 85. the 100 MIGHT have more low-end to it. im 5'4'' and 108lbs. riding a 00' kx 125. i can BARELY touch both toes at the same time. itd take some getting used to for her if she got a 125( the kx is also smaller than the rm, yz, and cr[ only the sx is smaller]). also, on that comment about the kx 100 ( properly geared) could only hit 55-65mph. ive heard of 85's hitting ( source: dealers, testers with radars, others) 75-80mph. the 100 should not hit much higher because of the slight difference in power: weight ratio.