Hard to find HP information...

[Micahdawg]

I read a 250 MX shootout that rated the 2004 RM250 at 44.5 RWHP stock. I've also discovered that the YZ450 puts down 46.9 RWHP stock. I think that speaks highly of both bikes.

So I was wondering how much power you could expect the 2004 RM to have with basic upgrades in place. Say a pipe, silencer, reeds (Rad Valve vs. V-Force?), filter and jetting.

I really enjoy the two strokes, and it would be nice to see some thumpers get slapped around a bit.

Micah

PS. Does anyone know what HP the 2003 RM250 put out? I can't find any numbers at the wheel.

 

[SpectraSVT]

Hp doesn't matter much. Just look at the CR250 and YZ 250. CR makes more HP but lacks good feel on the track. Yz is avg on HP but has the best engine on the track. Good dyno #'s don't always translate to a good engine on the track.

Figure out where you think the bike is weak and try and get the mods that fix that.

 

[Micahdawg]

Well...HP does count in a flat out drag race. My friends and I enjoy riding, and don't get all too competitive in the trails, but occasionally we get out into open stretches just for braggin rights on top end. Overall HP and torque curves probably don't matter much when you are bangin away in a very narrow peak HP range.

I'm sure the YZ would always come out victor on top end though since it's geared so much broader than my RM (and I assume even the new RM's).

Micah

 

[VB Racing]

What Spectra said, I have found that mods usually don't give a ton more power, they just move the power around, or broaden the power available.
For an example, I have an 01 KX250, the bike has good bottom to mid performance, but falls of the pipe pretty quick. I also ride alot of "woods" type riding, so I need a torquey and linear powerband. I have messed around alot with reeds, reed spacers, flywheel weights and pipes(I have owned 2 of these bikes). I never really felt that the bike had more absolute power, but it made power where I wanted it, and I made the bike alot more "rideable"
I guess what I am saying is that you don't need to worry about max "dyno" HP. Experiment with basic stuff, and you will
get a bike that fits you and your riding style.
Hope this helps

Oh and by the way you may get a couple horsepower peak out of the mods you described :thumb:
If you are looking for top speed, just lose a couple teeth off the rear sprocket, or go 1 up on the front, it will go faster if that is what your looking for.

 

[marcusgunby]

A 250 will have a peak similar to the 450 but its down everywhere else.Same as a 125 vs 250f.

the 2004 RM250 ive seen on the dyno only made 40 hp at the rear wheel but with mods it was 48hp-still doesnt match a well modified 450 but its more than most can handle.

 

[Mike's 2003 YZ250]

I have always wondered about top speed as well. What do you guys think the top speed is for a new BONE STOCK 250 2 stroke such as mine, or any other new BONE STOCK 250 2 stroke?? I was figuring about 75mph? How much faster could you make it with just a sprocket change? Mike :think:

 

[marcusgunby]

Actually its lower than that ,70 mph is what the 04 rm250 will do.
With gearing change i would expect around 85mph but it will be slower to get there.

 

[Mike's 2003 YZ250]

Thats it? Hmm, thats lower than I thought. 80/85cc bikes do like 60mph I think. I guess its all in the gearing. They dont gear these bikes to have high top speeds, they gear them to be on a race track. I just always had a "thing" for top speed, although I love how the bike can pull the front wheel up with ease in the first 3 gears. :eek: Mike :thumb:

 

[SpectraSVT]

2003 YZ250 tops out at 77mph with stock gearing according to Yamaha. Drop it 2 teeth in the rear and I think you can probably go faster than any sane person would want to go on a dirt bike.

 

[Mike's 2003 YZ250]

77, thats a good number! :) Now Im curious about this. With every tooth you go down on the rear sprocket, how many mph do you gain in top speed do you think? Maybe 5mph for every tooth down?? What would you "guess" the top speed would be on a newer 500cc 2 stroke bike? I know top speed doesnt mean all that much, but since we are on the subject already. :laugh: Mike

 

[marcusgunby]

Ive heard Smets KTM 570 does 65mph on one of the fastest gp tracks, also a mag tested all mx bikes back to back and the 4 strokes were scary fast-like 85mph with std gearing.

 

[VB Racing]

I know my WR400f and my WR450f were RIDICULOUS as far as top speed went. I saw as 90 MPH on some fast sandy trail on my trailtech with my 400, and my 450 would kick the 400's tail. I personally get kind of spooked at those speeds.
On a side note my WR450 will lift the front tire at 70mph with stock gearing!! :aj:
I will keep to the MX gearing on my KX, it's more than fast enough for me. :thumb:

 

[Enduro_Nut]

You can gear a 60CC bike to run 80mph if you have the gearing.

 

[Micahdawg]

Yeah, seems like the two strokes have a really tightly geared trans in comparison to the 4 strokes. This weekend I rode my friends YZ426 and the gears are so much broader. You can feel it from 1st on up. And when we race, we are usually pretty close to each other, then I hit 5th and top out.....and he just rolls into the throttle and pulls like he has another gear.

And that's when he cuts in front of me and I tuck my head down to avoid catching a mouthful of rock/dirt.

Micah

 

[Mike's 2003 YZ250]

This thread in my opinion was a really good one. One of the few top speed threads that didnt get closed. :cool: Im bringing it back to the top for the fun of it. Feel free to add some more info to it as well. Mike :cool:

 

[91kx]

I've got a DB mag from 99 that says the following:

CR500 -89mph
Husaeberg 600 -98mph
KX500 -86mph
KTM380SX -85mph
YZ426f -87mph

Several issues later they did some 250mx bike and they were around 75-77mph.
Cycle World tested the 2003 wr450f at 90 and the 450exc at 98 or 99mph.

 

[Mike's 2003 YZ250]

:cool: Great added info! Thats some fast machines. I wonder what the gearing is on those 2 stroke 500s? They sure do some fast top speeds. Mike ;)

 

[500guy]

KTM 495 has the record

I think the KTM 495 was around 136MPH, has a lot to do with gearing (obviously) and aero. The old 495s put out around 65HP. I have owned 2 KTM 500s and they put out about the same.

 

[2smoke]

Where did you get those rear wheel HP figures?? As far as I knew the Japs always quote crank readings where Euro manufacturers tend to quote gearbox readings.....just for info I think you loose roughly 7% between a crank and gearbox reading.....more again by the time it gets to the rear so Im a little dubious about those figures being at the back wheel.

 

[dirt bike dave]

I think the KTM 495 was around 136MPH, has a lot to do with gearing (obviously) and aero. The old 495s put out around 65HP. I have owned 2 KTM 500s and they put out about the same.

The old dirt bike test where they geared the 495 'to the moon', the top speed was 123.75 mph. Still a lot faster than I ever want to go on a dirt bike!

 

[CK]

top speed

Top speed is gearing limited on the bikes you're talking about. My old CR 500 was supposed to do 89 mph stock according to magazine tests. It had plenty of power to go faster, but the gearing would have been too tall for typical riding. I had a Husky 430 way back when and it actually scared the heck out of me. I never reached its top end. It was supposedly able to reach 105+ stock.