KX125 Woods Conversion

[Defy]

Any help?  I grew up riding 4 strokes and tooling around in the woods.  Some of my friends had 2 strokes and they would smoke me so i always wanted one.  So i finaly bought a KX 125 (to start with i will get a 250 after i build up some confidence) and when i first test drove it i thought it was broke becuase the was no bottom end but i had a friend check it out and said it was fine.  Where i live now i will be doing more woods riding rather than taking it to a track so i was courious what should i do?  From searching the past post everyone said buy a gnarly pipe, FWW, and re gear.  is that all?  Thanks

Nick

[The Flyin Hawaiian]

I rode enduros on a 2000 YZ 125 and did pretty much the same mods that you have listed except for the fww. I did have a V-Force reed cage. Which helped out a bit in the low end. The reason I didnt use a fww was because I felt it would bog the engine down too much on a 125. Also, and this may sound funny, dont run too big of a rear tire because this too could bog the engine. Stick with the oem size. Depending on the year, a company called Athena makes bolt on 144 big bore kits for 125s for about 5-600 bucks. You have to ride 125s pretty agressively to overcome their inherant lack of low end. Keep it singing, work the clutch and row through the gearbox. 

[KXcam22]

Defy,
  Theres lots you can do to pump up the bottom end.  It will never be a tractor but should be fine for woods riding.   Here is what I suggest (in order):

skid plate (you can make this easy for cheap)
rad guards (the cheap ones work just as well as the big $$ ones)
bark busters
flywheel weight (most bang for the buck on a small engine)
larger rear sprocket (add 2 teeth)
reeds (boysen dual stage (low cost) or vforce (higher cost)
Gnarly pipe.

You will notice that I have the guards first.  With the bike (and you) protected you can hit obstacles with more momentum with greater peace of mind.  Hope this helps. Cam.

[Defy]

rad gards are they like the plasti fins that are on my bike?  Or should i get metal ones?  i have ordered metal hand guards and a fww so it looks like i need to make a skid plate!  Any one have templates? 

[lhazc]

ok, is  FWW  the fly wheel weight?   not seeing/understanding how that could help that much.... ?? what does it do.   i see that many people use them but dont know why...    what all do you have to take off to put one on?  how do you know where excatly where to put it and are there different sizes??   thanks

[Defy]

--Help for stalling
Basicly the a light flywheel is easier to spin/stop spinning there for when you let off the clutch it doesn't have much moment to keep it spinning so it's easier to stall than a heavier flywheel. 
--Low End
Same concept the heavier flywheel takes longer to get up to speed so it gives you that low end but robs the highend.  I don't have the need for the really highend because i can't get the thing out of 4th in the places i ride. 

Looks really easy to install just search FWW and you will find pics.

Thats my stab at it, someone tell me if im wrong. 

[eprovenzano]

It helps to keep the rear gaining traction instead of breaking loose.  On my 250 I run an 11oz FWW.  It is very easy to install.  If you put on on your 125, I'd go 6-7oz.  Any more than that I think would rob power vrs helping the bike in the tough terrian.

[megad]

what year bike, and what's your weight?

I've got a 2003 kx125 setup for the woods, there are some issues

the 2003 lacks bottom end power, this is a huge issue and I gave up on the bike because of this, it's now my wifes bike, I have a ktm 200

the forks need a revalve, I just did mine and posted the shim stack I'm trying next


for mine I did..

bark busters
narrow protaper bars
scotts damper
12tooth front 51 rear
pro circuit type 296 spark arrestor silencer (still LOUD for my taste)
9oz flywheel weight
coil advanced position
back on stock pipe now, quieter and toned down the hit
hinson clutch setup with steel plates
fork revalve

that's all I can think of, the only real issue is when your on a steep hill climb, 5 diamond stuff, if you drop off the pipe the power drops sooo fast you will stall, heavy clutching helps but it's very hard to stop wheelspin doing that  I'm 200 pounds that did not help, the on/off power on the 2003 also is a real pain when it's wet

I'm really glad I upgraded to a ktm 200 it's better in every way

[Defy]

yeah the more and more i look at it i should have either got a bigger bike or went 4 stroke for what i am doing.  The bike is a 2001 Kx 125 and im am about 165.  I am looking to put either a 7 oz or a 9 oz fww weight and add one tooth to the back and run it like that.  I really like the speed of the th bike thats why i went with the 125 instead of the 250 (i wheelied the 250 like 5 times in a row and i said too much for now)  I still haven't decided what i am going to do i need to put brakes and a rear tire on it to get it back too good order then i might sell or trade for a 4 stroke about the same size.  well see. 

How is the 9oz FWW?  Do you think that would be too big for me? 

[eprovenzano]

I'd go with the 7 oz FWW.  Don't despair, I think you may be happy with the 125.  If set up correctly they are a great bike.  The proper gearing is very important.  Run a 13 tooth front sprocket, and a 49-51 in the rear.  Add good tires, and just have fun.  The 125's are so light, that you can throw them around and don't be mistaken, that can pack a punch when ridden hard.

[megad]

9oz is not enough for me, I need a 12oz to tone down the massive hit on the 2003's  wish I had known that before i bought it

7oz is really small, that's what people put on kx65's

[kxaddicted]

hm what r bark busters?
and how long would it take it rebuilda 250 motor and put in a new piston/ring???