rm 125

[rmrider45]

need new piston and ring ?

hi i just bought a used 2003 suzuki rm 125 and have been riding it for about 3 weeks. the guy i bought it from said it was never rebuilt and has the same origonal piston and ring. my ? is if i put a new (standard) piston and ring in the top end will i see a difference in power ?. i have had some friends ride it and they say the front end should pick up and it dont . like i said its all origonal .thx

 

[rmc_olderthandirt]

You might notice a slight increase in power with new rings, but it won't be dramatic.

If you wait for the piston to fail, however, then the difference will be dramatic. So will the impact on your pocket book.

The ability to lift the front wheel ("pop a wheelie") is more a factor of technique than anything else. Slip the clutch, keep the engine on its power curve, shift your weight back and you can lift the front wheel.

Rod

 

[rmrider45]

You might notice a slight increase in power with new rings, but it won't be dramatic.

If you wait for the piston to fail, however, then the difference will be dramatic. So will the impact on your pocket book.

The ability to lift the front wheel ("pop a wheelie") is more a factor of technique than anything else. Slip the clutch, keep the engine on its power curve, shift your weight back and you can lift the front wheel.

Rod

i know what you mean about letting the piston fail . it would damage the cylinder and cause a mess.

? if i say get it bored 20 over and a new 20 over piston and ring then will i see a major increase in power.. also do i need to get the cylinder sleeved or i can just get it bored


just putting a new standard piston and ring in without bore i will see no power change?

 

[rmrider45]

any ideas ?

 

[rmrider45]

i just bought a used 2003 suzuki rm 125 and have been riding it for about 3 weeks. the guy i bought it from said it was never rebuilt and has the same origonal piston and ring. my ? is if i put a new (standard) piston and ring in the top end will i see a difference in power ?. or do i need to bore it say 20 over

 

[rmc_olderthandirt]

a "20 over" bore job is such a small percentage change that I really doubt that you would notice the difference. I certainly wouldn't bore it out if it didn't need it because you can only bore it so far and then you have to re-sleeve, which costs a bunch.

Rod

 

[Backslayer]

depends on what kind of compression you have got now if a new top end will give you more power, but it will only restore whats lost if any not give you anymore, If your wanting more power, I highly recomend Eric Gorr. www.forwardmotion.com.mx.

 

[eds_tls]

If its been ridden regularily and never been apart its overdue for a top end.

If its not running strong you may have other problems. Dirty air filter, clogged exhaust, poorly tuned carb etc.

My 125 has enough power to move my 190 lbs around pretty good. I rarely get out of 2nd gear in the trails. The only time I wish I had more power is when I'm going uphill.

Have you ridden other 125's before?

 

[Chili]

It will all depend on the condition of the top end and my guess is you'd be hard pressed to tell the difference between stock and 20 over. Also keep in mind this isn't a steel bore so you don't just bore it out and slap an oversize piston in there you need to get the cylinder replated if you bore it.

 

[_JOE_]

Your cylinder is plated. You cannot bore without a replate. Nothing will majically give you a "major" increase in power. Unless the compression is so low it's barely enough to keep it running. You can send the cylinder to a reputable engine builder and have it ported to shift the power curve wherever you want it. Most people percieve a pipey, top end power curve as "fast" becuase the power comes on quickly in the mid-top.

 

[rmrider45]

If its been ridden regularily and never been apart its overdue for a top end.

If its not running strong you may have other problems. Dirty air filter, clogged exhaust, poorly tuned carb etc.

My 125 has enough power to move my 190 lbs around pretty good. I rarely get out of 2nd gear in the trails. The only time I wish I had more power is when I'm going uphill.

Have you ridden other 125's before?

i am 160 lbs and it does take me around ok mostly i never get out of 3rd gear on tight trails . thats my problem when going uphill it seems to not have power like it should.i would have to try to ride another 125 to see the differnce.air cleaner is clean new plug etc .just seems uphill i have to stay in first gear and clutch it sometimes


Have you ridden other 125's before? no but 2 friends rode it and said it dont seem to have balls

 

[whenfoxforks-ruled]

If the bore is okay, a fresh top end should give you a good pull from off idle. When its shot, it will have a "light switch top end".

 

[Chili]

A 125 rarely has much for bottom end and to climb hills on one it's all about momentum otherwise you'll be burning up the clutch trying to make the top. You can do the top end on that bike for less than $150, throw in a fresh top end since you are unsure or at least check the compression.

We had Eric Gorr port my sons 05 RM125 for a low end setup like he did for a Pro Supercross racer and he really liked the setup much more than the stock 03 RM125 he'd had previously.

 

[rmrider45]

. You can send the cylinder to a reputable engine builder and have it ported to shift the power curve wherever you want it. Most people percieve a pipey, top end power curve as "fast" becuase the power comes on quickly in the mid-top.

so its better to repiston /ring it and get the cylinder ported and polished ?

porting the holes in the cylinder for more power ?

 

[_JOE_]

You will see more of a difference from a fresh piston and porting than the overbore. Wait till you damge the plating, then have it done cause it's only like 80 bucks more to bore the cylinder.

As Chili said, low end porting is great for tight areas such as SX or woods. If you ride MX or fields/fire roads alot, top end power is more useable.

 

[rmrider45]

You will see more of a difference from a fresh piston and porting than the overbore. Wait till you damge the plating, then have it done cause it's only like 80 bucks more to bore the cylinder.

As Chili said, low end porting is great for tight areas such as SX or woods. If you ride MX or fields/fire roads alot, top end power is more useable.

thx joe .thats what i will do get a fresh piston and ring and send it out to get ported

what area do they port and what does it do?


lately thats where me and my son ride in the woods on trails

but sometimes we go to the coal hills and old striping pits

 

[_JOE_]

They can change the shape and height of the ports which alters the "port timing" shifting the power curve. Lots of folks have had great success with Mr. Gorr. You may want to consider having the 144 service done. Eric ports the cylinder to compliment the bore and can alter the compression ratio with head mods for whatever fuel you run. Check it out....http://www.ericgorr.com/supermini144BigBore125service.html

I believe that entails some case mods that aren't extremely difficult and don't require splittng the bottom end.

 

[rmrider45]

They can change the shape and height of the ports which alters the "port timing" shifting the power curve. Lots of folks have had great success with Mr. Gorr. You may want to consider having the 144 service done. Eric ports the cylinder to compliment the bore and can alter the compression ratio with head mods for whatever fuel you run. Check it out....http://www.ericgorr.com/supermini144BigBore125service.html

I believe that entails some case mods that aren't extremely difficult and don't require splittng the bottom end.

thx but i thought you said i dont need to bore out the cylinder? just to get it ported . also i didnt think the head needed to get stuff done to it

i was thinking new standard piston and ring and just porting

 

[_JOE_]

thx but i thought you said i dont need to bore out the cylinder? just to get it ported . also i didnt think the head needed to get stuff done to it

i was thinking new standard piston and ring and just porting

That would be the most cost effective option.

The 144 is less cost effective as the actual gain in cylinder volume is minimal for the amount of money it cost to replate. The porting is what makes or breaks a two stroke engine. Reguardless of how much displacement you have the engine won't run right without proper porting.

 

[rmrider45]

That would be the most cost effective option.

The 144 is less cost effective as the actual gain in cylinder volume is minimal for the amount of money it cost to replate. The porting is what makes or breaks a two stroke engine. Reguardless of how much displacement you have the engine won't run right without proper porting.

ok great i know some good machine shops in my area

do i give them the cylinder and the head or just the head

thx so much

 

[m4i2k2e2]

if your so concerned about power why not just sell it and get a 250. i ride pits and trails with a 250 and my CR has plenty of power to bring were i need to be. why waste all kinds of money on sending things out to ported and polished? when you get it back its still not gonna be like a bigger bike. maybe a decent difference in power. how much expierce to you have on a bikes? if your not familar with the bike you may not think it has balls. once you learn how to ride it you might. be careful to with 125's you tend to have to work the clutch more for hill climbing, you dont want to burning out that.

what kind of bikes do your friends ride? if they all ride 450f's there all gonna think you bike has no balls.
-mike

 

[2-Strokes 4-ever]

Rode/raced 125's in the woods for years... Porting is worth looking into. Shaving a little material off the base of the cylinder to lower the port height will help a lot (head may need work to bring compression back to stock.) Advancing the ignition as much as you can get by with will help. Low-end designed reeds help. Slide in 2-3 more exhaust manifold washers before the pipe goes in (more "head pipe length" creates low-end.) Add a couple teeth to the rear sprocket. Make sure you're dialed in with the jetting, being crisp on the pilot and needle is good. 125's are a ton-o-fun, replace clutch plates often. :cool:

 

[_JOE_]

if your so concerned about power why not just sell it and get a 250. i ride pits and trails with a 250 and my CR has plenty of power to bring were i need to be. why waste all kinds of money on sending things out to ported and polished? when you get it back its still not gonna be like a bigger bike. maybe a decent difference in power. how much expierce to you have on a bikes? if your not familar with the bike you may not think it has balls. once you learn how to ride it you might. be careful to with 125's you tend to have to work the clutch more for hill climbing, you dont want to burning out that.

what kind of bikes do your friends ride? if they all ride 450f's there all gonna think you bike has no balls.
-mike

Alot of people like the idea of having the machine perform to it's full potential. Why port a 250 when you could just go buy a 500? There's alot of reasons a smaller bike is better for some people. Some people like the reduced weight of a 125. Some people like the fact that you can get a little tired and sloppy on a 125 and not have it take you for a hellride due to a slip of the pegs or something. Some people like the power surge of a top end tuned small bore. Sure is alot cooler sounding than a 500 when you crank em up. Maybe he has spent a bit of money on other parts for his bike and doesn't want to gamble on another used bike when he could really wake up the one he has for less than 500 bucks.

Listen to 2 stroke for life, he has a few more good ideas. Watch who you let machine/port your cylinder. Make sure it's someone who knows DIRT BIKE ENGINES. Make sure they have a good reputation.

 

[rmrider45]

Alot of people like the idea of having the machine perform to it's full potential. Why port a 250 when you could just go buy a 500? There's alot of reasons a smaller bike is better for some people. Some people like the reduced weight of a 125. Some people like the fact that you can get a little tired and sloppy on a 125 and not have it take you for a hellride due to a slip of the pegs or something. Some people like the power surge of a top end tuned small bore. Sure is alot cooler sounding than a 500 when you crank em up. Maybe he has spent a bit of money on other parts for his bike and doesn't want to gamble on another used bike when he could really wake up the one he has for less than 500 bucks.

Listen to 2 stroke for life, he has a few more good ideas. Watch who you let machine/port your cylinder. Make sure it's someone who knows DIRT BIKE ENGINES. Make sure they have a good reputation.

thx again joe .as you said >>Some people like the reduced weight of a 125. i do like the light weight of a 125 .250 s 400s
seem to heavy . i dont want to hold up a bike that weighs a ton.i thought i would write this thread due to the fact the guy i bought it from said his son raced it 8 or 9 times and he told me that the motor was never touched. the reason i got the bike is to go out with my 11 year old son he has a 2003 rm 85 bored to a 105 and it flys .that 85 takes me around like i am a fly .lots of stuff was done to his bike tho from the origonal owner .jeted carb ,bore ,ported i would say. the bike would keep up with mine with no trouble ..btw i havent spent any money on the bike sinse i bought it a 2 months ago

i paid $1200 for it. i think i got a good deal ? what you guys think. the bike is in great shape :) pro taper bars brand new kenda back tire , renthal chain and sprockets , 909 levers etc.

 

[_JOE_]

Nice bike. Yeah, if you're just rippin around with the boy I would say just throw a piston in it and call it good. Is that the stock pipe?