Hey I'v got a 04 cr125r and just got the top and bottom end down on it ($950). I went out on orv trails for the first time with it and wasent impressed on how it does in tight trails. I did get some upgrades for it like fmf fatty, fmf shorty and vforce reeds but are not installed yet. I don't want to install them just yet because I'm thinking of just selling the bike and returning the parts and getting a 250 4 stroke.

Do you think that putting the upgrades on it will make this a better trail bike (lower end power) or should I just try to sell it after I just put $950 in top and bottom end and get a 4 stroke bike. Jason  

The 125 doesn't have a lot of bottom end to begin with.  That being said, are you getting all it has to give out of it?

Properly adjusting the airscrew does wonders for the throttle response and lowend.  Also - putting on a rear sprocket with a couple more teeth does wonders too!  

I'm kinda new to 2 strokes and adjusting stuff on it. Its been tuned by a honda dealer prob when it got the top and bottom end done on it. Do you think the upgrades will do a big difference?  

The FMF fatty will make some difference in the bottom end.  I would hold off on the reeds and silencer for now.
A bigger rear sprocket will make the biggest difference of them all though!

Don't count on your dealer to have set your carb right.  For one - most of them don't do it, for two - if they do it, they do it wrong, and for three - the airscrew needs to be adjusted every ride - it's not a 'set it and forget it affair'

Now to the meat of the matter - you don't like how it runs on tight trails.. be more specific - what's it doing that you don't like?  

I already have all them parts I listed sitting in my house just not installed yet. its just really bad on low end power in the trails. no get up and go intell its at a little higher RPM because i'm not going to fast because its alot of turning. I dont know how to adjust the carb at all. I even have a manual and i'm still lost. like the jet sizes I dont even know where to get bigger jets at.  

The bigger rear sprocket will get it into the higher RPM (more power) at slower speeds - this really helps on the trail.  The FMF fatty will boost the lowend a bit.  The silencer won't make much of a difference, and the reeds will only help mid-to high RPM power.

For the jets.  Turn the fuel valve off. Then tip your bike all the way over to one side to drain the gas out of the float bowl (about an ounce of it).  The take the 17mm bolt off the bottom of the carb.  This will allow you access the main jet and the pilot jet - they are small brass pieces that screw into the bottom of the carb.  The air screw is on the left side of the carb, nearer to the back of the carb. it's also brass and is turned by a flathead screwdriver.

Proper jetting is CRITICAL for good performance - low, mid, and high.  A lean bike will bog when you open the throttle, and a rich one will not get into the revs cleanly, and will foul plugs.  The Honda manual does a wonderful job of explaining how to get to your jets, and has pictures too!  

I'v rode the the bike, And ride nothing but woods and trails. Depending on your age and stature...? You will not be happy and have a issue with jetting with the weather. Like i said, Need your riding Exp and stats to really say.  

jasonman17:
Hey I'v got a 04 cr125r and just got the top and bottom end down on it ($950). I went out on orv trails for the first time with it and wasent impressed on how it does in tight trails. I did get some upgrades for it like fmf fatty, fmf shorty and vforce reeds but are not installed yet. I don't want to install them just yet because I'm thinking of just selling the bike and returning the parts and getting a 250 4 stroke.

Do you think that putting the upgrades on it will make this a better trail bike (lower end power) or should I just try to sell it after I just put $950 in top and bottom end and get a 4 stroke bike. Jason

A 125 is light flickable and powerful for it's size.  You need to learn how to play it to its strengths.  As a small bore 2 stroke it needs to be on the pipe to make any useful power.  At first this will be hard in tight trails, but over time you will learn how to meter the throttle to get the bike doing what you need it to.  Taht is why Skip says to use a bigger rear sprocket.  It will get on the pipe at slower speeds, and give the engine more torque to play with.  (like using a longer wrench)  The pipe is a good one and should be put on.  The smaller silencer will mostly just make more noise as you will hardly tell the difference.  I also say to take back the reed cage if you can.  The stock one should be sufficient for what you are riding.  Spend that money on protective equipment for you and your bike.

A 250 fourstroke is not the perfect answer you are looking for.  They are easier to ride with a wider spread of power and enjoy more torque provided by the bigger piston.  They also run hotter and will overheat in the tight trails.  A fourstroke will be harder to turn, and feel heavier overall.  The will also cost more in the end.

I'm not a total fourstroke hater.  I loved the old XRs for trail riding.  The newer CRFX, and WR models look to be good reliable bikes as well.  

I have an 04 cr125 w/ stock sprockets. My friend has a 91 cr125 w/ oversize rear sprocket. I have ridden the 91 and the bigger sprocket makes a big difference on the off idle power.

Riding a 125 through tight trails can be an unnerving experience because you have to stay busy w/ clutch and throttle. If you are looking for a lazy ride tractoring through woods the 125 is not the bike for you.  

If you ride trails most of the time. I would consider getting a four stroke, WR250's are really great for trails. Most any four stroke will be a lot more fun to ride on trails.  

Thanks this helps out alot!! so what number rear sprocket should I get? 91 or bigger? Jason  

what size do you have now?  It will be stamped on the sprocket - like 49 or something near that.  

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I'm looking at this website and it says the my stock sprocket is 52 and 13  

I would go up to a 54 or 55 tooth. It don't take a lot of change to make a big difference.