125-200cc Some questions about the CR125 / WR125

Hi all!

new forum reader, I've been lurking for a few days just reading. I don't own a Husky nor have I ever, but let me start with a bit of background.

vital stats: Intermediate class rider, 25 years young, been riding and mountain biking since I was a little kid, 130 lbs without gear, 5' 10.5", very mechanically apt (own a BMW repair shop).

Long story short, I come from a mountain biking background so off road, weight is a priority. I currently have a 1989 Honda NX250 (6 sp, 250 four stroke, dual sport) that I use as a straight up trails bike. 95% of the time I trailer to the trails and use the dual sportability to link up via roads. Occasionally use it to bomb a couple miles around town before hitting trails. I've pared down the weight from around 290 to about 260, but I find a couple things lacking: suspension, mostly. Weight is still piggish to me at 260 (I know, 260 isn't that heavy). I don't ever do motocross nor will I ever have any of my bikes on a track. Not my style of riding.

I ride almost all tight gnarly single track with as much elevation as I can get my hands on. I ride Wisconsin, northern Michigan, northern Kentucky, and southern Indiana, though I live in Indianapolis.

My other bike is an 07 KTM 105SX. There was an XC of this bike, but it had sprocket changes and a kickstand and was much rarer. The SX is the same motor, same tranny, etc. All I've done is sprocket changes. I haven't done a flywheel weight, haven't done a lighting coil or dual sported it (though I'm contemplating it). the bike weighs in at 150 lbs dry, probably around 160 wet. This is awesome to me. The chassis size I'm very comfortable on (super mini). I don't mind the 16/19 wheels (the NX has 16/19's stock too). I only weigh 130 lbs so I'm large-kid sized.

I really couldn't care less about weight while I'm riding. Heck, a 290 lb NX feels great when you're blasting down a trail and even better on the highway. But when I'm stuck in a mud pit (of which there are plenty in the midwest), I freaking hate dead-lifting that much weight. Riding on dual sport tires (even aggressive DOT knobbies) means the bike gets dropped a lot. If my riding time gets cut to 6 hours when I could be riding 8, all because 1/4 of my energy when to picking up the bike, that sucks.

Ok, so what's the issue? One, the KTM 105 is a peaky motor with a super close ratio tranny. The motor will never be a lugger, it isn't suited for woods riding (in it's current form), and despite the amazing 16 inches of ground clearance and 12 inches of suspension travel, the motor just isn't the right motor for what I use it for. Forget trying to slam a 125 four stroke motor in there, they're too big. I've measured. My motor is freshly rebuilt, so it isn't an issue there. Even with 130 lb rider + 160 lb chassis, the 290 lb package doesn't have that oomph at lower rpm's and I'm not a wind-it-out type of rider.
Two, the type of riding I do demands wide ratio. I can't really gear down for the woods then jump on a fire road and wind the motor out for 3 miles.

So what's the plan? I want to drop a WR125/CR125 motor into the frame. I love the CR125/WR125 chassis size, love the 18/21 wheels, love that I can get a repairable bike for under $1000. I don't love the 220-230 lb weight. I might as well ride my NX. However, a WR125 motor in a Kato frame....I have access to a great machine shop, master welders, full suite of tools, etc etc etc. I've read the best things about this Italian 125 - luggable with some adjustments, mods are known and easy to do, and I've read some pretty amazing first hand accounts of their durability and reliability.

so questions:

1. I'm assuming I want a motor from around 02-07 right?
2. Did 02+ CR/WR have the same tranny?
3. Did 08+ CR/WR have engine or tranny improvements?
4. Is 02-07 WR flywheel/stator the best for lighting? I've read that they have a 100+ watts of power. This is important for running dual sport gear
5. Can the 02-07 CR125 motor be fitted with a WR125 flywheel, stator, and (probably) flywheel cover?
6. Is the flywheel and stator the only difference between the motors during that year range?

Please bear in mind that basically any motor would get torn down to have the water pump drive gear and impeller replaced, seals and bearings redone, tolerances measured, replace the piston, etc.

I don't mind picking up an extra 10-20 lbs in the motor if I need to. that's well worth it to me.

Thanks for your knowledge in advance! I'm sure I'll be posting more questions as I delve further into this. Hopefully you all can chime in on a build thread very soon!

-J

First thing you should do is buy a 09 and up cr125 ride it, then tell me if you really want to put that wonderful motor in a lesser handling chassis. If that doesn't convince you put them both on a scale to see the difference you might be surprised.

I understand how he feels. I love my CR for the motocross track. Best bike I've ever owned, but it just feels too big in the woods, so I'm looking for a KTM105.

I can totally understand that sentiment, especially for an already rare(ish) bike. I don't plan on tearing apart a perfectly good bike for the motor if I can help it.

However, at 130 lbs soaking wet, it isn't a matter of if the bike is too big. I already know it is. I really like the Kato 105 chassis, handling, suspension, and I plan on getting the suspension set up correctly if I pursue this route. It turns nicely and has amazing ground clearance already. There aren't any other supermini's out there unfortunately - maybe the KX100 with 25 year old suspension, KLX140 or 110, TTR125L with YZ85 forks and shock...no other big wheel super mini's. The difference between picking up a 230 lb bike is a world apart from a 160 lb bike. I can pick the Kato up from a drop with *one* hand....and I don't think the CR125 as it sits would be a problem in the woods if I was using knobbies. I can handle 1 or 2 drops with a heavier bike, taller seat height (Love the NX for it's current 34 inch seat height unloaded, even with a taller rear shock and larger rear rim and tire)...but I won't be riding this bike with knobbies. I'll have 50/50 like a TW39/40 or a Shinko 244.

and as I said, from a mountain biking background, I'd ride an 80 lb bike if I could squeeze enough power and traction into the chassis. Already considered a Motoped and I just don't want to go that way quite yet. Dirt rider says a 2010 WR125 is 233 lbs fully fueled. My Kato should measure up at 160-165 as it sits.

Here are some of the reactions I've gotten so far:

"That bike won't work, it has too short a wheelbase" - doesn't concern me. I don't need high speed stability crawling around the woods
"You'll be top heavy cuz the bike doesn't weigh enough" - how do mountain bikes manage to go 50 mph on downhill mtb courses? They only weight 30-45 lbs!
"No torque, gutless, 1/8 liter, blah blah blah" - yep, but for a 130 lb rider on a 170 (with the swap, guesstimating) lb bike, that weighs less as a package than most bikes do by themselves. No need for a lot of power moving around a small amount of weight
"Can't do it, that's a KIDS bike" - I'm about the right size!!

i say do it & post a step by step report with bulk photos!

Have you looked into modifying the current 105 motor for more low end power? Porting, compression, carb, or a FW weight would probably all help tame it a bit.

I have. I've thought about having eric gore do the porting as the cylinder is a day or two away from being sent to Millennium for replating. Steahly makes a flywheel weight for it. The carb is an unknown - nobody tries to tame these things for the woods. Raising compression would help, o-ring head so you'd have to do it via machining the head or lowering the base gasket thickness. I have given these some thoughts.

The other option is the tractor of a KDX200 motor. Easily accessible, huge torque out of the box, rebuilds every 2-3 years instead of every year, etc etc. The WR125 and KDX are both close ratios in my opinion though. Jumps are around 9 mph at peak power, ie 27-36-45 mph in 1st 2nd 3rd. My NX goes from 27-43-57-73 1st through 4th. That's the trans I want in a bike with 30-40 HP and tractable torque (125, 200).

bump, because I'm still wondering about the differences between a WR and a CR in the early 00's year range. I don't see the point of going newer than 07 - the motor remains basically unchanged. Stator swappability, watts of output, trans ratios, differences between the models? Surely someone has a bit of knowledge they can pass on.