134/139 or 144 on an 04 RM125

[ebeck]

Seems I read alot of stuff here and there about 134's being better than the other big bore choices on 125's but I am pretty sure that information was years old.

I assume the 04+ RM with no exhaust bridge eliminates some issues that may have existed with th RM.

I sent mine to Eric Gorr today, can still change the bore size, he will not recieve it for a few days.

I find it odd that Max power only offers the 144 for the YZ. Am I missing something about the 144's?


The question:

On an 04 RM125, is there any compelling reason do do a 134 or 139 over the 144 bore? Piston lightness perhaps?

Thanks.

 

[robwbright]

Eric's 144 piston weighs 1/2 ounce more than a stock 125 piston. I wouldn't be concerned about that.

Get the 144 and be happy!

Here are a couple of my posts from when I first got the motor back from Eric.

http://www.dirtrider.net/forums3/showthread.php?t=126800

http://www.dirtrider.net/forums3/showthread.php?t=133418

And yes, when I can afford it, I intend to buy a 250f. . . Or maybe a 280f. ;)

School loans and family expenses are calling. . .

 

[helio lucas]

nothing to do with piston weight... think about a 250 or a 500..
some bikes only require boring to get the 144cc, others , by different reasons, also require stroking... this makes it very expensive, so, some people stays by 134 or 139, whatever we can get just with boring...
some time ago was very difficult to get bigger pistons...

also if the cylinder is just bored without porting the bike just get low end, and the bigger you bore more low end you get without an increase in top... some times even with a decrease in peak power

 

[ebeck]

helio lucas, I am not following. Piston weight has ALOT to do with reliability and the ability to rev into the higher rpm's.

If you can get a 144 with just boring, which you can, piston weight then becomes one of the the biggesst factor to consider.

robwbright, I was searching for RM144 not RM 144, thanks. Do you think it will pull a 13/51 which is the same as a 12/47?

 

[hot125mod]

hey rob do you need to have the cylinder stripped then eric does the port work and then it needs to be replated for 185 thats cheap I mean if you were to have just porting no big bore. the plating will flake and be ruined i just thought the nicasil was awfully hard to be grinding on.

 

[robwbright]

I sent the complete motor to Eric and he did all the work - bore, plating, porting, head work, case mods, etc. . .

I don't know what he's charging now (2+ years later), but for me it was $450.00 for everything.

Well worth it.

Given the fact that Eric lets you choose the type of porting you want, I wouldn't think it would be an issue between 139 and 144. The RMs go to 144 bore only with no problem.

I'd like to try a 155 stroker. . .

Rob

 

[robwbright]

Also, Eric designed the 144 piston for Wiseco. . . And he designed a special plating for Suzuki cylinders.

 

[ebeck]

No 139 available for Eric Gorr for the RM125. He said 144 is no problem. I stuck with the 144 mod. With the 04 motor it should be bananas. I also opted for the broader powerband porting (little here little there) as opposed to top or bottom end porting (all here or all there). The 04 had no problem with power anywhere as it is, it was really broiad by 125 stanards. It was the first year KTM copy motor. More everywhere porting should be really good. I got the race gas head too. Muahahahaha :)

 

[hellbertos]

Hey ebeck. Make sure to do a followup post once you break it in and get a solid ride on it. I have my eye on an 05 RM125 that I'd like to turn in to a 144. I'd love to hear a ride impression from you.

 

[ebeck]

Sure no problem. EG got the motor today. :)

 

[250racing]

hey i own a 04 144 got my kit from eric last year. its great no reliability issues and the power is broad and manageable i usaually ride hilly mx tracks and enduro singletracks on the stock bike i had a 52t rear sprocket now i run a 50t rear sprocket and the powerband is still better from idle to top.

on my local dyno my bike is 3 to 4 hp more powerful than the 250 f bikes around my area some even have fmf slip ons.

 

[robwbright]

on my local dyno my bike is 3 to 4 hp more powerful than the 250 f bikes around my area some even have fmf slip ons.

Unfortunately, you (and I) also have a lot less torque than a 250f. . .

But 144s are definitely fun!

 

[250racing]

Unfortunately, you (and I) also have a lot less torque than a 250f. . .

But 144s are definitely fun!

i dont care about torque the rm 144 is a bike that can circle around a rmz 250 and i have never liked the fart machines. they feel
sssssssssllllllllllllllllllllllllllllllllllllllllllloooooooooooooooooowwwwwwwwwww
they are perfect for novice riders with no corner speed or big bucks pros and im neither of those.

 

[robwbright]

the rm 144 is a bike that can circle around a rmz 250

I like the 2 strokes as much as the next guy, but I'm afraid you're going to be unpleasantly surprised. . .

 

[250racing]

I like the 2 strokes as much as the next guy, but I'm afraid you're going to be unpleasantly surprised. . .

i have the chance to ride the bikes side by side. my brother owns a 2008 rmz 250 and i have never been able to come to grips with how the 4 stroke bikes handle. engine wise i dont know i dont feel at a disadvantage on the 144 as i did on my 125 keep in mind the 250 f´s arent heavily modded here. at the most they get an fmf or pc slipon and thats it.

btw im around 140 pounds so maybe if somebody is 175 or 190 maybe they would rely more on the torque of a 4 stroke. but for me on diferent tracks the stopwatch doesnt lie and it says im a bit faster on the 144

 

[helio lucas]

i´m sorry if i don´t explain well...

your right, the piston weight is critical to the max rpm...
what i want to say is that most of the time the added cc´s will increase the performance more than the added piston weight will decrease, so there is a clear advantage...
maybe not in max power but in better power...

my point is that the porting will made the greater difference when it cames to big bore... or maybe the cost of big bore, and to a less extent, the piston weight...

http://justkdx.dirtrider.net/125dyno.html

i think this will speak for me...


once again sorry for the mess... :cool:

 

[ebeck]

The 2004 Eric Gorr RM 144 with race gas head and “mo better everywhere” porting which is designed to broaden the power band is what I got. Here is my overall impression of it. It is strange.

You know how a 125 is frantic and pipey, well it is no longer like that. I mean it is, kinda, but kinda not. I mena the pipe is still there it is just not in your face. In truth the bike feels slower. I mean that in a good way. Remember, I said it "feels" slower. One thing I noticed first off is that I am ripping through the gears up to 4th gear as I always do and I never really felt myself get there. You know the frantic 125 hit and scream, yet, at the same time, I was saying to myself dayuuum, I am freaking going fast here. It seems like I got there faster. Like I said, it is strange. It is like a 125 but not really yet it is. Feels slow but you go fast, faster. It is pipey but the pipe starts sooner and is broader and with less hit comes less sensation of speed.

Another thing I noticed, you can go into a corner and drop the speed without needing to down shift. Half way though the turn just start to roll on throttle. If you get stuck or bog too much, a quick stab or two of the clutch and good night! No need to downshift.

The bike also does has extra oomph to help throw you over long table tops, it is just not super noticable. it is there though. At 180 pounds that really helps. You know how to clear jumps on a 125 you have to hit the jumps balls to the wall(assuming your not 130 pounds) where a 250 can just lug along and throw itself over the jump with a twist of the grip on the face? Well the 144 is better than a 125 but not as good as a 250 in that regard.

Overall the power is noticeable and really improves the bike everywhere. The difference is not in your face blatant but more subtle. My 150 pound 450F riding buddy remarked “that thing has the juice now! That thing has power everywhere!” Yeah, I would agree, power is broader yet it is subtle at the same time.

I’ll tell you what it does do though. It makes riding it a hell of a lot easier. I am not sure of that is good or bad though. I liked the frantic nature of the 125. I do not want a 250. So, the good thing is that the overall character or personality of the 125 is not gone, it is just calmer. It does all the 125 things, it just easier with less panic. The hit is less yet you go faster. Turns are easier but not 250f easy. Like I said, it is kinda strange to ride.

I sum it up like this. You notice the effects of the power more than you notice the power itself. If that makes sense.

Would I do it again, oh yeah, you betcha. :nod:

Not sure why img tags are not working but here is a shot of the 144.