New 2002 cr125

[kmr296]

Hey everyone. I'm new to the site and to dirt bikes. I've wanted to get into riding for a while but am just now at the place where I can afford a bike. I wanted to start off slow so I got a used 2002 cr125r from a buddy dirt cheap. Its got some bruises but overall is in GREAT shape. The pipe on it is now stock but is not like a high performance pipe. I think he put one on he had around to see if it would better the performance. I know NOTHING about bikes, but plan to change that. I've ridden for years but never anything of my own or for a very long time. I rode today for like 7 hours and had a blast - can't wait to get on it tomorrow.

Got a few questions. I had some trouble getting up some steep hills today. (I'm sure a big part of it is my lack of experience) The thing seems to lack bottom to mid power. Top end is great - its plenty fast for me when I'm wide open. But for trails where I am and my experience level that's not the best thing for me to be doing. What can I do to get some power here? Everything I read says basically porting and exhaust. What is porting? Where can I get it done? How much have you guys paid to have it done? Does anyone recommend any exhaust for this bike? Also would it be a good idea for me to maybe drop a tooth or two in the back?

Like I said I am a complete newbie with bikes. I'll take any advice I can get. I plan on tearing the thing apart and cleaning/relubing everything this week - can't wait to tear into it.

Thanks

 

[XRpredator]

it's a 125. The lack of bottom and mid power is the nature of the beast when it comes to a 125 two-stroke. You gotta keep the sucker revved to the nuts to make it work right.

 

[_JOE_]

The clutch is your friend. Use it to meter power delivery. Basically, hold the engine in the power band and use the clutch to drive the rear wheel. Use it to cut power if you feel it's getting away. You can't expect a small bore 2 stroke to pull down low. A pipe, porting, reeds, compression and jetting will help the mid range power. The power valve may be adjustable as well.

 

[kmr296]

Thanks guys. That makes sense. I learned through trial and error that the clutch control is key.

So I know what a pipe, compression and jetting are. Whats porting and reeds?

And whats a power valve? Wheres the adjustment? On the carb?

 

[_JOE_]

Go get a service manual, it will show you how to adjust the power valve. The PV controls exhaust flow allowing the engine to make more low-mid power. It is basically a mechanical restrictor in the exhaust port. You should see a cover on the side of the cylinder near the top front. Most of them can be adjusted to open earlier or later in the rpm range.

Porting is the cutouts in the cylinder that allow fuel/exhaust to enter/exit the combustion chamber. By grinding or epoxy build-up a tuner can shift the power around.

Reeds are between the carb and cylinder. They are usually fiberglass stock. They bolt to a cage and open when the engine draws a vacuum. The close to allow the engine to push fuel into the combustion chamber. There are dual stage(two layer) reeds that usually help bottom end a bit. Some companies such as Boyesen or Moto Tassinari(V-Force) make complete cage setups that offer a bit more performance.

 

[kmr296]

awesome. Thanks joe. My dad and I plan on rebuilding the thing before summer. His buddy races and wins a LOT in his class. he's like 50 and knows a ton. I've been talking to him a lot today and he said the same thing you did. I'm gonna look into these. Thanks a lot man

 

[Patman]

Don't worry about an exhaust on that bike the stock Honda setup is pretty darn good. If you want the bike to feel like it has more bottom get a flywheel weight, it's won't change the amount of power just the way it feels and will help keep you from stalling in the slow stuff and on hills (both up and down). Also look really hard at a JD Jetting kit for the carb, out of the package it was the best bucks we spent on my son's CR125. Read the directions, select the proper pieces based on your riding and environment and you will be amazed at how clean that bike will run. Also look at the V-Force intake (reeds & block) again this will help the bottom end power and the ability to apply just the right amount for a given situation.