'03 YZ 125 Mods?

Joined
Sep 8, 2003
Messages
18
Likes
0
#1
Hi, I was lookin to upgrade my '03 YZ 125 bike from stock.
What would be the best thing to upgrade first, or second for more power?
Pipe,Silencer
Reeds??
Piston??
Anything else?
 
Joined
Jul 27, 1999
Messages
22,688
Likes
507
Location
Chicago
#2
Jetting should be your first step, none of that bolt stuff means anything till you get it jetted properly.
 

john stu

Lifetime Sponsor
Joined
Jan 7, 2002
Messages
790
Likes
0
#5
jetting a bike is just making sure its running the correct air to fuel ratio do a search on and you will find all kinds of answers. as for mods that bike rips i would spend my money on first of all keeping the bike fresh (tires,top end,maintenance)and then if i had extra money i would get a skid plate,good chain,a good set of bars that won't bend in the first tip over like the stock ones and if you really want to spend money have the suspension set up just for you (riding ability and weight)not untill all that if there is still money left then i would worrie about doing engine mods even then i would not do a pipe untill i smashed the stock one i would first do internal mods like a reed cadge or adding a tooth to the rear sproket or even porting why spend $200 on a pipe when if you fall over (and you will) you can smash it when you could buy a reed cadge or porting or gearing that won't get wrecked in a crash.
 
Joined
Sep 8, 2003
Messages
18
Likes
0
#6
Maybe I shouldn't mess with anything till stuff starts breaken and maybe a new piston. I may try jetting it but mine seems to run fine.
 
Joined
Mar 3, 2002
Messages
30
Likes
0
#7
What do you wanna do with the power? More power? Or just more top-end power? I don't really like porting, because you never can change it back. You can really do something with the top-end with a VHM cilinderhead. You can change the combustion-chamber (more or less compression) and give the bike more top or bottom-end.
 
Joined
Jun 25, 2000
Messages
378
Likes
0
#8
This kind of things really scares me. A guy buys a brand new bike and want to buy all fancy aftermarket parts aswell and doesnt even know how to rejet. Some people seem to think they can buy speed(skill).

To gain from more power you have to be really skilled to gain more than just a second on the straights that you will lose anyway when you have to brake earlier for the corner. The good guys wont be much faster than you on the straights but they will keep the speed much more though the corner. Look on the good guys in the 125 and 250 class, its a matter of seconds between them and twice as many cc.
Invest in correct valving and springs for your suspension. I bought new valving for my forks and the result was that i coulnt ride twice as long at what feels like twice as fast and crash only 1/5 as much. Thats a good $150 and thats what you want. More power is probably the last thing you need.
 

bclapham

Lifetime Sponsor
Joined
Nov 5, 2001
Messages
4,340
Likes
0
#9
Originally posted by pyromaniac
This kind of things really scares me. A guy buys a brand new bike and want to buy all fancy aftermarket parts aswell and doesnt even know how to rejet.
me too, if you dont know how to change the jets on a bike then you have no business changing pipes and reeds. learn to maintain the bike first. the best thing you can do is read the manual and also buy eric gorrs book on dirtbike maintainance
 

Rcannon

Subscriber
Joined
Nov 17, 2001
Messages
1,886
Likes
0
#12
It is easy to feel like a person needs a new bike, hot parts, etc to compete. It is much easier to buy pipes than to practise.

A few weeks ago I watched a good rider run away from darn near everyone. His bike was a 1992 CR 500. Virtually stock.

Buy a good shop manual. It amazes me to see the amount of hopped up bikes that have never had the shock linkage greased,