Well, I am unimpressed

[pdiddy]

So, Dirt Bike and Dirt Rider have just been falling all over themselves praising the CRF250X. Now, I am sure it is a fine bike, but after reading the latest Dirt Rider, I dont get it. The bike is $6000, weight 243lbs, and only has 30hp according to the FMF dynojet graphic in Dirt Rider.

My KDX was $4000, weighs 222lbs, and, with an aftermarket expansion chamber, will put out around 30hp I belive.

The CRF has better suspension I am sure, but I am glad I went with the KDX! Suspension and the happy button isn't worth $2000 for me! :aj:

Long live the KDX! :yeehaw: :thumb:

 

[canyncarvr]

Ridden one?

I have.

Comparing the two is pretty much an apple'n-oranges deal.

The suspension is delightful. That's a fact. It's very narrow...much slimmer than the tank-heavy kdx.

It doesn't have the 'hit' that a 2-smoker is used to. Yeah...what 4-stroke does? The power delivery is completely different. If you like smooth, sure and strong...a 4-stroke is likely to give you that. When the going is steep and slippery the chances are excellent that a 4-stroke chugger will be passing up the wheel-spinning, pipe-hit, looping, clutch fanning 2-stroke.

Still, I can't argue with the fact that it's fun passing up my riding buddy on his new -x on my '..ugly green toad,' (he said. ;) ) Ha! Of course, that's only on straighter gravel roads. He can outride me any day of the week anyplace else.

But then, I had as much fun passing him up on his katoom 200 exc, too! ha-ha summore!

.....I've got a sideache!

Ugly green toad indeed. I just smile as I hop past him....

Seriously, comparing ponies to ponies is pointless. I'm sure you know that. The delivery of the power is so different as to be......well.....completely different.

It's a nice bike!

I won't be buying one.

BTW, I've spent well over $1000 on my kdx suspension. When you start adding up what it takes to make the kdx run, it does just that. Add up.

 

[70 marlin]

Ridden one?

I have.

Comparing the two is pretty much an apple'n-oranges deal.

The suspension is delightful. That's a fact. It's very narrow...much slimmer than the tank-heavy kdx.

It doesn't have the 'hit' that a 2-smoker is used to. Yeah...what 4-stroke does?

canyncarvr: Come ride my Berg, The 470 will jump out of your hands if you twist it too quickly! :clue:

 

[canyncarvr]

I'm sure it will.

:clue: So will the 250-x! Twist it too quick and you will be sitting on your backside in the dirt.

Still, it's not the bandwidth 'hit' that a supercharged pipe-effected 2-stroke has.

Ever see a 4-stroke with diverging/converging cones on the pipe? No? Why not?

Cuz they don't work that way.

 

[levert]

Isn't supercharging using a mechanical compressor to raise pressure and flow from the intake side.Wouldn't a pipe be more of a device that scavenges the flow out of the exhaust port?
Just a question.

 

[levert]

Wow, supercharging is a term used for the pipe and scavenging on a two stroke.I thought I was so smart,DUD on my part.

 

[canyncarvr]

Guess you answered your own question.....anyway...

From here:

That completes the chain of events for the basic two-stroke cycle. The discussion is not complete. The animated demonstration has an added device commonly known as an expansion chamber attached to the exhaust port. The expansion chamber (an improperly named device) utilizes sonic energy contained in the initial sharp pulse of exhaust gas exiting the cylinder to supercharge the cylinder with fresh mixture. This device is also known as a tuned exhaust.

There are several animations on the web that give you an excellent graphical representation of how a 2-stroke works. Some include the effect of the pipe, some don't.

However......

From here:

"supercharging" means supplying to the working space, e.g. cylinder, combustion-air pressurised by means of a pressure source, e.g. a pump.

(note the spelling of 'pressurised' for starters! ;) )

At the top of that page is:

COMBUSTION ENGINES (cyclically operating valves therefor, lubricating, exhausting, or silencing engines

..either of which might make you wonder about the verity of THAT content. (Thassa joke, son!)


Specifically, the term is described as:

The verb "supercharge" has 2 senses in WordNet.

1. boost, advance, supercharge -- (increase or raise; "boost the voltage in an electrical circuit")
2. supercharge, pressurize, pressurise -- (increase the pressure on a gas or liquid)

(That from here: )


I guess this could be argued, but I think of 'scavenging' as only part of the 2-stroke expansion chamber operation.....being the removal of spent gasses by the positive wave brought about by the diverging cone. The negative (return) wave brought about by the converging cone is what does the gas-stuffing (supercharging, or the '..increase the pressure on a gas...') back into the cylinder.

Thanks for taking the time to actually look for information on the term...as opposed to asking 'Just a question.'

 

[levert]

If I'm wrong I always owe up to it.

Being around four strokes so much I'm used to certain terms being applied only too them.I should have known better!!

 

[JasonWho]

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[canyncarvr]

Levert:

Well then, own up to that one, too! ;)

..kinda like, 'Tough road to hoe.'

Or, 'Coming down the pipe.'

Uh...not exactly.

It's row and pike.

 

[skipro3]

I think Levert was just getting his merds wixed, oops, words mixed, and ended up sounding like a turd of hurdles, I mean a hurd of turtles.
Dang! now you got me doing it.
p.S. CC, how about a report on what you got for suspension and why. I just dropped $700 for race tech to plush up my KX forks and stock rear shock. They ain't back yet so no report from me until then.

 

[louis]

Wow! All that just for a honda. Anyway, I rode one also. I was impressed with the power and the suspension and most of all it has the button.

 

[Rcannon]

The more I ride, the more I want to build up ont of the KDX/KX hybrid bikes the folks here post about.



I think it would be the best of all worlds!

 

[levert]

Wow !

Spelling and grammer mistakes aside, I was totally incorrect in my assumption of the correct meaning of supercharger.
I already apoligized if I seemed harsh or critical, truly my reply was only meant to be a quick response written in about 5 seconds, I'm really sorry if I hurt anyone's feelings.

Your intentions Canyncarv are duly noted.

 

[CaptainObvious]

I'm interested in hearing how well the 250X stands-up over time. More specifically, I know that my KDX will get 100 hours out of a top end, but what's the longevity of a high strung 4-stroke? The overhaul cost is well known for my KDX - whether you do the work yourself or have a mechanic wrench for you - what will an overhaul on the 4-stoke cost. I KNOW that I won’t be doing the top end on the 4-stroke, that's for sure.

But in the end, I'm sure that I will have to get a 4-stroke. Last month I was at a harescramble...the sound meter showed me way off the acceptable scale. I'm done dropping money into my KDX...it can be improved no further without a major (read - stupid) cash infusion. It already has a main-line into my wallet.

I will NEVER sell my KDX (once again, I have too much into it – plus it makes a nice guest bike), but right now I’m saving my pennies for a CRF250X, or hopefully a KDX250F.

 

[Crispie0]

RV6Junkie - what do you have on your bike that you didn't pass the sound test? What decibals did the test read?
Just curious, I'm going to a race this weekend and might need to bring along spare parts. Thanks!

 

[JasonWho]

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[Rich Rohrich]

Ever see a 4-stroke with diverging/converging cones on the pipe?

YEP. I just walk downstairs and look at the pipe I built for my YZF Supermoto :rotfl:


You can't see the converging (or reverse cone) at the end of the diverging cone in this picture, or the diverging cone at the front but they are there. :nener:

 

[Rich Rohrich]

I'm interested in hearing how well the 250X stands-up over time. More specifically, I know that my KDX will get 100 hours out of a top end, but what's the longevity of a high strung 4-stroke?

The suggested service interval is in the 15 hour range for the piston and rings. We just did a 250R with about 5 months/60 hours of regular hard riding on it. The piston ring (there is only one) was blowing by like crazy and the valve seat was hammered to twice the service interval limit. So far the Honda 450s don't appear to be throwing parts through the motor when you stretch the intervals, but the 250R/X is still pretty much of an unknown in this area.

They do get really SLOW and sluggish when the rings wear, so it's easy to know it's TIME.

An hour meter is a wise investment on these bikes.

 

[CaptainObvious]

RV6Junkie - what do you have on your bike that you didn't pass the sound test? What decibals did the test read?
Just curious, I'm going to a race this weekend and might need to bring along spare parts. Thanks!

I have a PC pipe and a shortened stock silencer (removed the reverse flow section). To be honest, it's not any louder than any other aftermarket (performance) silencer since it's basically the same thing...a well packed perforated tube. Of course, a spark arrestor (which is what mine was) would be quieter.

For measurement, they were using the meter at a 45 degree angle, 4 feet from the pipe. I think I was around 105 db's at 1/4 throttle. The tester, trying to help me, said "ahh, don't rev it so much" so I just cracked the throttle...and still failed at 102 db's. I gave the tester dumbfounded look and said something to the effect that it must need to be repacked (even though I just repacked it) and he had mercy on me. Lots of riders had socks tied to their pipes.

The bike doesn't seem any louder than any other bike, but like I said above, I'm not going to quiet it down. I'll just park it if I have to. I've come to the realization that it's just an old-school bike.

 

[CaptainObvious]

The suggested service interval is in the 15 hour range for the piston and rings. We just did a 250R with about 5 months/60 hours of regular hard riding on it. The piston ring (there is only one) was blowing by like crazy and the valve seat was hammered to twice the service interval limit. So far the Honda 450s don't appear to be throwing parts through the motor when you stretch the intervals, but the 250R/X is still pretty much of an unknown in this area.

They do get really SLOW and sluggish when the rings wear, so it's easy to know it's TIME.

An hour meter is a wise investment on these bikes.

That's good info Rich. I ride my woods bike (KDX) about 25 to 50 hours per year, so you can see how expensive a four stoke could get. Of course, if I had a new woods bike, I'd ride it closer to 50 hours! I'm hoping to see a service interval in the 25 hour range.

It's not the short service intervals that bother me. My KX125 is a 25-hour topend bike. But I can change the piston and rings on a friday night for a minimum expense. I'd have to get some training to service the 4-stroke.

 

[JasonWho]

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[Rich Rohrich]

That's good info Rich. I ride my woods bike (KDX) about 25 to 50 hours per year, so you can see how expensive a four stoke could get. Of course, if I had a new woods bike, I'd ride it closer to 50 hours! I'm hoping to see a service interval in the 25 hour range.

It's not the short service intervals that bother me. My KX125 is a 25-hour topend bike. But I can change the piston and rings on a friday night for a minimum expense. I'd have to get some training to service the 4-stroke.

At a more moderate pace than an expert MX'er rides there should be no reason why you can't get those service intervals from the rings and pistons. The Yamaha 250Fs have the nasty habit of breaking parts and throwing them through the motor if you stretch the intervals to long, but so far at least the Hondas have not shown any of that behaviour. They just get slow and hard to start when they are really tired.

These engines are much easier to work on than most people might realize, but it will never be as simple as popping the top on a CR125 and changing the piston. But if you think about it, a water cooled power-valve equipped 125 seems like a bear to work on when compared to an old air-cooled Elsinore. ;)

 

[kmccune]

But if you think about it, a water cooled power-valve equipped 125 seems like a bear to work on when compared to an old air-cooled Elsinore. ;)

Those were the daze! :cool:

 

[JasonWho]

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