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Does the KDX 200 motor swapped into a KX125 chassis make a better woods bike than a 144cc Athena kit with a flywheel weight added to the KX125 motor?

I never rode a 125 in the woods let alone one with a BB.
But from what I hear, yes, the 200 would be a better engine than the BB 144, the tranny is different and geared for wood riding while the 125 is geared for MX.
My 0.02

scheckaet wrote:I never rode a 125 in the woods let alone one with a BB.
But from what I hear, yes, the 200 would be a better engine than the BB 144, the tranny is different and geared for wood riding while the 125 is geared for MX.
My 0.02

Thanks. I am more or less thinking about the difference while racing harescrambles, where the tighter trans ratio might actually be better. I race a Husky WR250 right now and am thinking that a lighter/lower power bike might be more fun.

I have ridden an '05 YZ125 in the woods quite a bit. In more open areas the YZ does well. In the tight rocky hilly sections that I prefer, it completely sucks. This is because it has very little torque, and the gear ratios are designed for staying on the pipe as you would on an MX track. Lots of revving and tire spinning makes for an expensive and tiring way to ride.

The attractive thing about the YZ is the awesome suspension and very light weight. This is exactly why a hybrid makes sense in the woods. Who knows why Kawy didn't update the KDX with a modern suspension and a weight loss program, but they didn't. The wide ratio tranny and good powerband of the KDX motor in a modern frame sounds pretty ideal. Putting a 144 kit in a MX bike solves about a quarter of the problem. You're still not going to get the grunt of a 200 or 220 KDX, and you do nothing about the tranny. On top of that, you're still going to have to rev the thing, and that's what makes little motors need piston changes as often as they do.

Ditto everything Mike said. Staying on the pipe in a hilly curvy tight section of woods is downright frightening. You really need to be able to lug the engine to stay in control in many sections, especially in HS or Enduro. You hardly ever see a 125 running Hare Scrambles, BB kit or not.

I'd like to ride one of the new TM 144 Enduro bikes though. I imagine they have built the motor more for woods riding.

This is the whole reason I built my hybrid. I also ride a Husky CR 125 with enduro mods. The Husky motor is surprisingly flexible. It can be lugged down pretty well, and it has a ripping top end. I really like it in flatter woods. It's tough in the hills, however. The low end just isn't powerful enough to get you up any significant climb. Staying on the pipe takes real commitment sometimes, and lots of times I can't if it's too technical. The 200 motor is much more flexible. Torque up a technical climb using the low end? Check. Rip up a climb on the pipe? Also check.

dfeckel wrote:This is the whole reason I built my hybrid. I also ride a Husky CR 125 with enduro mods. The Husky motor is surprisingly flexible. It can be lugged down pretty well, and it has a ripping top end. I really like it in flatter woods. It's tough in the hills, however. The low end just isn't powerful enough to get you up any significant climb. Staying on the pipe takes real commitment sometimes, and lots of times I can't if it's too technical. The 200 motor is much more flexible. Torque up a technical climb using the low end? Check. Rip up a climb on the pipe? Also check.

Cool. You should sell it to me...

dfeckel wrote:This is the whole reason I built my hybrid. I also ride a Husky CR 125 with enduro mods. The Husky motor is surprisingly flexible. It can be lugged down pretty well, and it has a ripping top end. I really like it in flatter woods. It's tough in the hills, however. The low end just isn't powerful enough to get you up any significant climb. Staying on the pipe takes real commitment sometimes, and lots of times I can't if it's too technical. The 200 motor is much more flexible. Torque up a technical climb using the low end? Check. Rip up a climb on the pipe? Also check.

Another question for you - Does your hybrid still feel flickable like the Husky 125? The KDX motor is probably a full 10 lbs heavier than the 125 motor... Can you feel it???

I really like my WR250 and it is a very respectable 247 lbs wet and race ready. The 125's just feel so light, it's almost like riding a mountain bike! I don't want to build/buy a hybrid and end up with a bike that feels similar to my WR250...

I think the hybrids are generally lighter (10-15 lb?) and more flikable than the stock kdx; dunno if it's AS flikable as a stock 125 though, never ridden one.

I'll let you know about the hybrid's relative flickability after my ride this weekend--I'm trying it out in the super tight stick farms of NJ for the first time.

REgarding the 125? Yes, it's SOOO easy to change direction on that bike. I have found myself many times narrowly missing a tree with just a little body english that on my old 4-stroke TE would have put me solidly into bark sample territory. So light. I'm hoping the hybrid is as good.

dfeckel wrote:I'll let you know about the hybrid's relative flickability after my ride this weekend--I'm trying it out in the super tight stick farms of NJ for the first time.

REgarding the 125? Yes, it's SOOO easy to change direction on that bike. I have found myself many times narrowly missing a tree with just a little body english that on my old 4-stroke TE would have put me solidly into bark sample territory. So light. I'm hoping the hybrid is as good.

Cool! Good luck!!

Colorado Mike wrote:I have ridden an '05 YZ125 in the woods quite a bit. In more open areas the YZ does well. In the tight rocky hilly sections that I prefer, it completely sucks. This is because it has very little torque, and the gear ratios are designed for staying on the pipe as you would on an MX track. Lots of revving and tire spinning makes for an expensive and tiring way to ride.

The attractive thing about the YZ is the awesome suspension and very light weight. This is exactly why a hybrid makes sense in the woods. Who knows why Kawy didn't update the KDX with a modern suspension and a weight loss program, but they didn't. The wide ratio tranny and good powerband of the KDX motor in a modern frame sounds pretty ideal. Putting a 144 kit in a MX bike solves about a quarter of the problem. You're still not going to get the grunt of a 200 or 220 KDX, and you do nothing about the tranny. On top of that, you're still going to have to rev the thing, and that's what makes little motors need piston changes as often as they do.

I wonder what the YZ ends up like if you put a 35mm PWK, the 144, flywheel weight, and maybe retard the timing a little?

I am not knocking your guys' hybrids at all - I would build one if I had the time & money. My Husky WR250 is a 2000, and it still has the older style wide ratio trans. Even though the motor has the TQ to lug from gear to gear, I feel that it would be faster (racing) if the gears were closer together - that got me thinking that while a wide ratio trans is great for trail riding, the close ratio might be better for racing...

Letitsnow--I'd consider selling you the 125!!

Oh, and I committed the cardinal sin of bike building earlier this week--I added up my receipts. D'OH!! It's so easy to spend more than you wanted to when you're buying parts individually...and no doubt I could have built a great bike for half the cost, but what's the fun in working MANY hours building a bike to end up with trashed plastic, old tires, stock suspension, worn grips, etc. You only live once!

dfeckel wrote:Letitsnow--I'd consider selling you the 125!!

If it were a jap bike and about 7 years older, it might be in my price range.

dfeckel wrote:Letitsnow--I'd consider selling you the 125!!

Oh, and I committed the cardinal sin of bike building earlier this week--I added up my receipts. D'OH!! It's so easy to spend more than you wanted to when you're buying parts individually...and no doubt I could have built a great bike for half the cost, but what's the fun in working MANY hours building a bike to end up with trashed plastic, old tires, stock suspension, worn grips, etc. You only live once!

AMEN brother!

scheckaet wrote:

dfeckel wrote:Letitsnow--I'd consider selling you the 125!!

Oh, and I committed the cardinal sin of bike building earlier this week--I added up my receipts. D'OH!! It's so easy to spend more than you wanted to when you're buying parts individually...and no doubt I could have built a great bike for half the cost, but what's the fun in working MANY hours building a bike to end up with trashed plastic, old tires, stock suspension, worn grips, etc. You only live once!

AMEN brother!

+1

How did the hybrid work in your Enduro???

A 125/144 could be great if you started with a 'blank' cylinder most likely. The jap bikes are already ported for MX, and there's some material you can't get back...One welded/epoxied up with an enduro porting profile might be doable. Bet $ on the fact that there is mafor porting differences between the TM125 MX and enduro models.