2 stroke vs 4 stroke what do you guys think?

[OZZIE_KLX]

Honestly who cares, ride what you like, like what you ride.

[iFR]

50hp? Show me one. Stock

[llamaface]

50hp? Show me one. Stock

the magazines all measure the ktm at 50 or more, but maybe they're lying. Anyway, unless you're some drag-racing fancyboy that doesn't turn, hp is not all that important.

 

but whatever, it takes all kinds. some dudes are into fat chicks, some dudes like 4strokes.....

Edited November 5, 2015 by llamaface

[jz125]

You should stop riding and stick to fishing

 

[OE800]

Modern 125 - 144 2 strokes make 35-40 hp, while the yz250 has been shown to be around 48 hp while the newer ktm 250sx has been claimed to make around 52 hp stock. Peak horse power for any bike is generally irrelevant anyways.

[chaos2767]

I jave had my share of both 2T and 4T and I enjoy the 2T more. I am not a racer just a casual rider and I love the weight saving over 4t and I can rebuild a top end for around $100 and do it in a fraction of the time. Its more cost effective for me since I have a family to support as well.

[Armbarn sailor]

Well I've ridden many bikes over the years, mainly 4T but sometimes i ride my friends 2T

Just to name a few :

2T

CR250

RM250

YZ250

KX 250

4T

CRF250L

YZ250F

KX250F

BMW 450R FI

RM450Z FI

YZ450F

YZ450F FI

RM450Z Athena 490

My bike is a YZ450 16 model ( previous was a 07) and to be honest, no bike compares to Yammys.

But WHY there's always some guy who goes "oh, a 450? Meh that's nothing compared to a 250 2T "

I mean ... Really?! Have you tried one at least?! Lol

A modern MX 450 makes 60HP ( YZ) and a 250 2T makes what? 38/40?

Yes , 250s are fun but nothing like a 450 brute force fun.

Curious enough, those who say 250s are way better, never really rode one 450

Yes nobody gives a shit and nobody cares, just wanted to get some out of my chest.

its a secret us Thumper humpers keep....yes, most certainly our 450s are faster and more predictable, more reliable, easier to ride fast.....but first they won't listen and second they won't believe. My 03 cr250 has an official dust jacket, hasn't been ridden in months...haven't even started it. I actually enjoy working on my 450 too, no gunk anywhere, just pure clean and shiny parts. Buuuuurp.....(new braaap replacement sound).

[Bmetz07]

50hp? Show me one. Stock

.

There's my old one? Ha ha. Not trying to start any funny biz but with a 300 kit man they are crazy

[The Spanky]

Well I've ridden many bikes over the years, mainly 4T but sometimes i ride my friends 2T

Just to name a few :

2T

CR250

RM250

YZ250

KX 250

4T

CRF250L

YZ250F

KX250F

BMW 450R FI

RM450Z FI

YZ450F

YZ450F FI

RM450Z Athena 490

My bike is a YZ450 16 model ( previous was a 07) and to be honest, no bike compares to Yammys.

But WHY there's always some guy who goes "oh, a 450? Meh that's nothing compared to a 250 2T "

I mean ... Really?! Have you tried one at least?! Lol

A modern MX 450 makes 60HP ( YZ) and a 250 2T makes what? 38/40?

Yes , 250s are fun but nothing like a 450 brute force fun.

Curious enough, those who say 250s are way better, never really rode one 450

Yes nobody gives a shit and nobody cares, just wanted to get some out of my chest.

38-40 hp from a 250T? I hate to break it to you, but a KTM 125SX makes that. 250Ts are in the 48-50 hp range.

Yes, 450s now make open-class-two-stroke levels of hp. The funny thing about that though, is most riders can't even use the hp of a 125 to it's full potential. Only the people that are earning their paychecks racing out of big rigs can effectively use the power of a modern 450F.

[BushPig]

38-40 hp from a 250T? I hate to break it to you, but a KTM 125SX makes that. 250Ts are in the 48-50 hp range.

Yes, 450s now make open-class-two-stroke levels of hp. The funny thing about that though, is most riders can't even use the hp of a 125 to it's full potential. Only the people that are earning their paychecks racing out of big rigs can effectively use the power of a modern 450F.

 

What is YOUR opinion of a good interval to top end rebuild a 250 smoker at?

 

Trail ridden, but with quite a few open sections including sand washes?

[Armbarn sailor]

What is YOUR opinion of a good interval to top end rebuild a 250 smoker at?

Trail ridden, but with quite a few open sections including sand washes?

20 hours total trail ridden.

[Bmetz07]

38-40 hp from a 250T? I hate to break it to you, but a KTM 125SX makes that. 250Ts are in the 48-50 hp range.

Yes, 450s now make open-class-two-stroke levels of hp. The funny thing about that though, is most riders can't even use the hp of a 125 to it's full potential. Only the people that are earning their paychecks racing out of big rigs can effectively use the power of a modern 450F.

Exactly I couldn't use the power of my 13 ktm 250 and now I have a 450. The power is unbelievable on both bikes. It's whoever is riding what they prefer.... I have no idea why some ppl get so mad about. Just enjoy what you got and let others have fun... Hodaka for life!!

[The Spanky]

What is YOUR opinion of a good interval to top end rebuild a 250 smoker at?

Trail ridden, but with quite a few open sections including sand washes?

You know as well as I do there's no magic "one size fits all" interval. I just do a compression test after breaking in a new top-end, and use that number as my baseline. I retest every few hours, and when I start seeing a measurable loss of compression, it's time. I generally go 40-45 hours on my KX250, but that's motocross, I'll bet I could easily go 100 hours or more with casual trail riding.

I should note that I do not re-ring pistons. If I'm going to spend the time doing a top-end, I'm putting new parts in it, my time is too valuable to me to waste it just slapping a set of rings in.

[CooHead]

Just took the motor out of my YZF250 for rebuild.

Been riding the KX250 two stroke in the mean time.

So different, so fun.

 

Since first ride day (April 18th) I have 21.6 hours on YZF and 3.9 hours on KX.

I'm partial to the newer four stroke as it is a better machine all around.  But the old (MINT) stock KX250 is tons of fun too.  Just more used to four stroke.  Guess if I road the KX 5times as much as the YZF, maybe I'd like that more.

 

But, either/both are great fun and good exersize.

 

Coo

[tractorman06]

What is YOUR opinion of a good interval to top end rebuild a 250 smoker at?

Trail ridden, but with quite a few open sections including sand washes?

I've got about 100 on my rmx and still have good compression I'll probably put a new top end on this winter when I pull the top end off.

[Armbarn sailor]

You know as well as I do there's no magic "one size fits all" interval. I just do a compression test after breaking in a new top-end, and use that number as my baseline. I retest every few hours, and when I start seeing a measurable loss of compression, it's time. I generally go 40-45 hours on my KX250, but that's motocross, I'll bet I could easily go 100 hours or more with casual trail riding.

I should note that I do not re-ring pistons. If I'm going to spend the time doing a top-end, I'm putting new parts in it, my time is too valuable to me to waste it just slapping a set of rings in.

I don't re-ring either, but I also don't use forged pistons in smokers. Cast pistons are lighter and create more snap. A stock piston will out perform a wiseco, a wiseco will last longer. A cast piston life for a cr125 in the Honda shop manual is 3.5 hours I believe. A cr250 is 12 I believe. A crf450 is 22 hours, and on stock rings that is about when you see loss of power, but a stock cast piston in thumpers can go 50 in my opinion, 75 to 100 some say. A wiseco or another forged piston in a smoker can go 50 hours, I still swap them at 25 because the rings wear when you ride sand and screaming a motorcycle is just going to happen. As a teen on 125s I rebuilt top end every third race, bone stock bike....never had motor issues when it came to a muscle match on the start or straightaway. That's mx. I also raced harescrambles, I would go awhile but guessing no more then 10 running hours. If you want a fresh and strong motor that will out perform some other bike that has money thrown at porting, pipe, and all that....keep a stock bike fresh. It's cheaper and better. I have sold a machine to a neighbor who didn't rebuild it for 3 years, it still started. It was a 250 I'm sure couldn't run down an 80 at that level of repair.

[The Spanky]

We've been over this before. First, ALL modern four-strokes use forged pistons, not cast.

I obviously can't speak about all models, but in many applications forged Wisecos are indeed lighter than the cast OEM pistons. In my KX250 there is only a 2 gram difference, negligible. But in my KDX250 there was a nearly 5 gram difference, and the engine was noticeably snappier and freer revving with the Wiseco.

Now given modern forging and casting technologies, there is far less difference than there used to be. Forged pistons are still stronger, but not by as much. Cast pistons are still more likely to break skirts, but not as much as was once the case. Forged pistons now run as tight or sometimes even tighter clearances than cast.

That last reason is why I run a Wiseco in my KX250. The specs for the cast OEM piston are .002" (.051mm), while the Wiseco Racer's Choice specs .oo15" (.038mm). And the Titanium nitride coated ring with that piston will outlast the piston.

Edited November 7, 2015 by Chokey

[Armbarn sailor]

We've been over this before. First, ALL modern four-strokes use forged pistons, not cast.

I obviously can't speak about all models, but in many applications forged Wisecos are indeed lighter than the cast OEM pistons. In my KX250 there is only a 2 gram difference, negligible. But in my KDX250 there was a nearly 5 gram difference, and the engine was noticeably snappier and freer revving with the Wiseco.

Now given modern forging and casting technologies, there is far less difference than there used to be. Forged pistons are still stronger, but not by as much. Cast pistons are still more likely to break skirts, but not as much as was once the case. Forged pistons now run as tight or sometimes even tighter clearances than cast.

That last reason is why I run a Wiseco in my KX250. The specs for the cast OEM piston are .002" (.051mm), while the Wiseco Racer's Choice specs .oo15" (.038mm). And the Titanium nitride coated ring with that piston will outlast the piston.

I wasn't saying anything about 4 strokes having cast pistons, I was relating rebuild requirements per service manual. Forged piston do last longer, but cast has always given a noticeable snap and performance gain. On the 01 cr250 I had, when I put the wiseco in it almost felt like I threw a flywheel weight on while I was rebuilding it. Cast gives noticeable performance advantage over forged, they just need rebuilt often. It's a choice one can make. I would rather have a fresh engine that came alive at the snap of a wrist then one that went 20 years on a rebuild. With the thumpers you are stuck with forged....but you can bump compression to damn near whatever you want....so who cares. On a smoker, a cast piston out performs a forged. That's not dyno tested, or charted in anyway. That's years of racing these diseased machines that have captured my soul.

[coastlinecascott]

Just short of blowing up my 450. Its going to be hard to jump back on the 250 2 stroke. 450 can spoil a person

[BDubb106]

We've been over this before. First, ALL modern four-strokes use forged pistons, not cast.

I obviously can't speak about all models, but in many applications forged Wisecos are indeed lighter than the cast OEM pistons. In my KX250 there is only a 2 gram difference, negligible. But in my KDX250 there was a nearly 5 gram difference, and the engine was noticeably snappier and freer revving with the Wiseco.

Now given modern forging and casting technologies, there is far less difference than there used to be. Forged pistons are still stronger, but not by as much. Cast pistons are still more likely to break skirts, but not as much as was once the case. Forged pistons now run as tight or sometimes even tighter clearances than cast.

That last reason is why I run a Wiseco in my KX250. The specs for the cast OEM piston are .002" (.051mm), while the Wiseco Racer's Choice specs .oo15" (.038mm). And the Titanium nitride coated ring with that piston will outlast the piston.

That is the exact reason I use Wiseco's in my 2 strokes. 15 hrs on the 125 piston, 40 hours on the 250 piston. Those are with cut heads and other misc performance mods to pump a few extra ponies out of the bike. All of my bikes require at minimum a blend of race fuel. I run it straight just for ease of use. I know it doesn't mean anything and I know my way isn't the ONLY way but works for me and I'll stick with it. People look at me like I am retarded when I say that typically forged pistons run tighter tolerances and are lighter these days. I actually didn't realize this until recently when reading through the paperwork, because I didn't realize they had changed so much. 

 

I used to be a firm believer in reringing pistons half way through my maintenance intervals but materials are so much better and tolerances are so much tighter that they just don't wear. When I pull my pistons there is virtually zero wear on the piston itself. Even rings, as you said don't wear like they used to. I definitely don't notice the piston slap when cold that I used to deal with, with the forged pistons because we don't have to wait for them to expand like we used to. 

 

To be honest though, at the intervals that most of us swap pistons and rings, we can run either without concern. I always say, it is more important to keep the bore within spec and make sure we achieve good ring seal than it is to worry about what type/ brand piston we run. Hell I have even run those cheap Namura pistons in a pinch with good results. Those only get a couple hours, if that put on them though. I don't trust them.

 

Oh, and I can't tell any seat of the pants performance difference between cast and forged. They throw roost just the same. I'm probably not the smartest for dumping a bunch of money into mods that produce more HP considering my bikes were  more capable than me in stock form, but I still believe that moving the power around will still benefit any rider. My 2 strokes are all tuned for max top end power, however there was a noticeable decrease in low end performance. My 450 is tuned for a monster mid range (because that is where they thrive and are the easiest to ride) and I can't say that I noticed any change in low or top end performance. If there was a change it was negligible. 

 

These piston debates are no better than the premix and oil threads that come along with them. They go hand in hand, but they are fun to talk about when someone actually "knows" what they are talking about. 

Edited November 10, 2015 by BDubb106