Bike Mods (Pipe?) for RM125

[BeauxJeaux]

I have a female friend who's a fast, aggressive rider. She likes the feel of a 125cc and has been riding Suzuki 125ccs mostly, and has a 2002 model now. She's about 5'2" and in good physical shape.

There are areas of our tracks where the 125 gives her advantages, but then there are places where she gets outpulled by 250s. She has ridden an '02 YZ250F, and although her lap times are good on it, it still felt a bit awkward and heavy and was tough to start. I just got an '03 YZ250F, which is definitely lighter and easier to start, and she'll try it out to see if it feels better than on '02.

But she thinks she will stay with the 125 because it's more to her style and she can be more aggressive on it.

So, there are actually two questions...

1) Are there any mods, probably an aftermarket pipe, that will give her 2002 125cc Suzuki more HP across the RPM range?

2) Are any of the female pro riders switching to the '03 YZ250F, away from 125cc bikes?

Thanks for your help!

 

[LoriKTM]

Moving to the 2-stroke discussion forum. I think you'll get a better variety of responses there.

 

[BeauxJeaux]

Well, I wanted to get some replies from other women riders about the YZ250F and if pro women were racing those bikes. That's why I posted the message on the Women Forum section. Your moving my message didn't help me in that regard.

 

[Lissa]

Does she compete? Motocross, Hare Scrambles or Enduros? I used to race 4str bikes. I got away from them because they can be very reluctant to start after a crash. A flooded 4str is about as useful as a paper weight and can take plenty of praying to revive. Usually by that time, at least 5 minutes has passed and about that many people passed you, too. Granted, all of what I said is based on the multiple 'kickstart' bikes I've ridden or raced. I switched to a 2000 CR250e ('e' for enduro). It takes two different riding styles for both machines. I can still move good on a 4str, but I have set my bike-up for good low end with a strong hit. This is very much needed in enduros and I personally feel it rounds out the rather shallow, but hard hitting power curve a 2str has. To build more torque you might have to sacrafice a little on top. What I have done to my bike is this: hard resin reeds (like Boyesen Torque Reeds) carbon fiber reeds are good for people that over rev their bikes frequently since they are less prone to chipping, resins are stiff and help create more low and mid range power. A fmf SST pipe or 'fatty' pipe will help increase low end as well as a longer silencer then stock. More back pressure adds torque making it harder for exhaust gases to escape. A exhaust power valve cover spacer (my CR has one, I can't remeber if they make one for the RM's or what the power valve set-up on one is like). If you have already rebuilt your RM and put a single ring piston in your bike (like aftermarket), thats supposed to help with over rev (less friction), I only use the stock double ring (less blow-by, last longer). Finally outside having Eric Gore port your engine, try playing with final gear ratios to tailor the power where you want it to be. Every one tooth on the front sprocket is like 3-4 on the back sprocket. Try adding a tooth larger rear sprocket (you'll need a new chain). You'll find additional teeth on the rear sprocket will bring the power lower in the gears. Don't forget all engine work (pipes, reeds, etc.) might require you to rejet your carb (especially pipe). Also if you have alot of time on your engine, do a top end rebuild, you'd be surprised by how many pony's you'll regain. 125 require rebuilds more often then larger bikes, something to the tune of two times yearly if your not racing. At least a 2str rebuild is dirt cheap (unlike my 4str which I blew apart several times)...Ahh, the beauty of simplicity. When it comes to bikes, just ride what 'ya like. They both have pluses and minuses. Good Luck, Lissa

 

[BeauxJeaux]

Lissa,

Thanks for your reply.

She races MX and places high in the A class. There are some younger ladies coming along that present a challenge, especially when some of them ride 250cc bikes.

You're definitely correct about the past 4-strokes. They were a bear to start. However, the '03 YZ250F is very easy to start, since it has auto-decompression, and possiblly other improvements. It's also about 7 pounds lighter than the '02 model. I can actually start it using a 2-stroke kick, and it seems to come to life everytime. So she's thought about the '03 YZF and will ride mine for comparison. I was curious if any other top women riders were converting to the '03 YZ250F since it is lighter and easier to start.

She has changed out to the Boyesen Torque Reeds and said that made a noticeable difference in power.

Do you have any personal experience (or know others who have) regarding which is the best aftermarket pipe for a 125cc 2-stroke? (in this case, it's a 2002 RM125). That seems to be the next logical step in gaining more power across the band. I know that aftermarket pipes for 4-strokes add considerable HP, but am not sure about 2-strokes. I've looked at Bill Pipes, FMF SST, and ProCircuit, but haven't seen a review of all three, so I don't know which is best.

I don't think that changing to a larger rear sprocket is the answer. One area she gets outpulled by 250s is in the long straight section, so she needs all the top speed she can get.

Since she revs her bike so hard, she does frequently do a top-end rebuild.

I think porting is not being considered, at least for now. That's pretty expensive and potentially shortens the life of the motor.

Thanks again for your response. I would definitely like to have more feedback on performance by specific pipe changeouts if the data is available.

 

[Vytas]

Porting is not expensive! Go and look at Eric Gorr's web site. I paid $110.00 for porting on my 2001 RM250, and it was the best mod I have done. This is one third the price of a pipe and silencer combo. How does porting shorten motor life? Do a search on this site and see how many riders/racers have had motor work done at Forward Motion. I have not seen one bad report about porting or motor work done by EG or that the motor had a shorter life span. Good Luck.

 

[bclapham]

Originally posted by BeauxJeaux
Lissa,
I think porting is not being considered, at least for now. That's pretty expensive and potentially shortens the life of the motor.

i dissagree slightly since its only expensive when you go with certain tuners. I had mine ported and a whole new top end kit (piston gaskets etc.) for $280 shipped to my door. Can she legally put an overbore kit, it seems like most people seem to run them anyway!

If she is doing regular top ends, there will be no problem with engine life! :thumb:

for bolt on power, most bikes seem to respsond very well to a SST pipe and more so to the V-force reed valve.

 

[flyinfinn]

bill's pipe for her rm! that's what suzuki factory 125 team uses.

 

[Lissa]

Porting doesn't necessarly shorten your top-end life span. And about gearing, I don't know how long these straights are that your talking about, but what good is top speed when you can't accelerate quick enough? Unless she's maxed out in sixth (or fifth, whatever how many gears it has) a gearing change might help considerably. When it comes to pipes, a aftermarket pipe may not do much more then smooth power delivery and add a little down low. Stock pipes now-a-days are extermely good, but I noticed have a harder hit then most after market pipes. Mostly likely because the after market pipe adds additional meat a little lower in the power curve smoothing out the transition. Anyway, my experience with aftermarket pipes is that the nickel finshes rust shortly after installation (or three enduros) unlike stock painted pipes (or ESR pipes, don't ask they proabaly don't make one). FMF has a nice choice of power curve tuneing pipes. SST or Fatty will proabaly do the trick adding the desired effect. Don't expect 4str low end power to magically appear, this is a high R (rpm) bike. The other pipes I'm unsure of since I only deal with getting more torque out of my bikes to scale rock faces and bar-bang between trees with ease. FMF offers (outside of ESR) the only pipes I'll pretty much consider because of their tunabilty, where other manufactures only offer one pipe per bike. Also Moto Tassanari (I think thats how it's spelled) has a tuneable reed cage. It is a pretty trick affair and I'm considering bolting one on and testing this winter at a couple southren enduros before the season starts back here this March. Your friend maybe should consider getting a 250 2str. I love the explosive power and use it to my advantage in the sand, but I still have enough bottom end torque to lug it in slimy rock conditions. There is even considerable riding style differences between a 125 rider and a 250 2str rider. Some of the fastest riders I know trash the trails on a 125, but its their 'never let off' riding style that puts it to use. You can't at all be lazy on a 125, or you'll get no where fast. 125 especially have a advantage in the turns where you don't have let off at all and just feed it more clutch to blast around it. My own riding style suits a 250 to a 'T'. I can't think of any other bike that is as easy to start, ride, or is as light for the power it makes. A blip of the throttle and it'll wheely just about any rock face or log I point it at. About 250s, do you mean 4str or 2str? Where are you's from, California? Are ya' talking about A class womens or mens? Out here womens class is womens class, no A,B,C stuff. I'm gonna race with the dudes next year so I can get advancement points. Anyway, There are no women here in enduros that I know of racing 250Fs. The mostly race 125s. Good Luck...Lissa

 

[BeauxJeaux]

Lissa, bclapham, and flyinfinn...

Thanks very much for all of your comments.

I was wrong about one thing. She did put in a larger sprocket several months ago, and said that helped significantly. So the mods she has made are the larger sprocket and the reed valve modification.

I'm passing on the comments to her that were made about porting. I've learned a few things about porting by reading all of this and by going to Eric Gore's site. Porting doesn't necessarily add power across the band. In fact, it can remove power. And it probably needs to be done with a specific pipe in mind.

She's going with a Bill's Pipe. I belive flyinfinn mentioned that the Suzuki factory guys use this. We were also at a race recently where the MotorcrossWorld Suzuki guys were, and they use Bill's Pipes on their 125 RMs. So, if Suzuki does it, that's got to be a good indicator.

Thanks again for all the comments.

 

[Lissa]

Suzuki sposored guys get Bill's pipe support, that's why they're using them. If your looking for more torque, a FMF SST or a Fatty will help create more ponies down low. About Bill pipes, contact them and ask the power charteristics of their pipe or if they offer mutilpe kinds (rev, torque, etc...) before purchasing. Remember if she's racing against riders of equal skill on 250 2str's, your gonna get smoked on the straights by the 250's. Except it, they got 15hp more! E-mail Eric Gorr about what would work best for her situation. He has big bore kits that really add a lot of additional bottom-end power. Porting does help all over. Eric has one for just bottom-end and another that boost power gains through out the power curve. Oh well, the best advice. Don't ride your friends bikes. They usually remind you how much your own bike sucks. Good Luck, Lissa