Picking chain, front/rear sprocket HELP!!

Joined
May 4, 2001
Messages
15
Likes
0
#1
I am gonna buy a new chain, front sprocket, and rear sprocket for my 1989 YZ 125. The only problem is, i dont know what to get yet, what chain would i get, how do i know how big i need it?? And about the sprockets, do you get more power with the more teeth your sprocket has or is it the other way around. someone please help me out.
 

HiG4s

Subscriber
Joined
Mar 7, 2001
Messages
1,308
Likes
0
#2
Several brands are good, I like RK.
Get an O ring chain
You don't necessarily want to change the gearing but if you do.
an extra tooth on the front sprocket will give you higher gearing.
more teeth on the rear will give you lower gearing.
less teeth on the rear will give you higher gearing.
 
Joined
Dec 10, 2000
Messages
1,490
Likes
1
#4
Originally posted by RC_Yz125
meaning ill have more low end power with a bigger rear sprocket?
Changing the gearing doesn't change the power output of the engine, it changes the power delivery . If your riding areas have a lot of places where you are constantly finding yourself in a situation in which one gear is too low but the next gear is too high, like you have to slip the clutch in third gear to go around a turn because second is way too low, then gearing down will allow you to pull that taller gear easier. Adding teeth to the rear sprocket (or subtracting from the front) will lower the overall gearing, and tighten up the gaps between gears, making it easier to run a gear higher than you have been, and the lower first gear will help reduce stalling for offroad riders in tight situations. The downside to this is it will make the power hit harder, and the engine will rev through the powerband quicker, which can be a problem if your bike already has a narrow spread of power. You will also lose some top speed, but this being a problem or not depends on where you ride.

I use Regina O-ring chains and Sunstar steel sprockets. The Regina chain that I run is very expensive, over a hundred bucks, but I get a couple of years out of one, so I think it is cheaper in the long run than using cheaper chains that wear quickly. There are many good brands of chains,m just shop around for what you think is a good value.
 
Joined
May 4, 2001
Messages
15
Likes
0
#5
also, how do i know what size chain to get for my bike and the sprockets that i will be using, a 420, 520 or whatever?
 

KXTodd

Subscriber
Joined
Nov 25, 2000
Messages
463
Likes
0
#6
I'll be due for new chain and sprockets soon so I'm glad this came up . I've been convinced to get an oring chain after reading about them so many times but have been wondering about the sprockets. Spanky your chain lasts that long, how about the steel sprockets? They last just as long as the chain?
 
Joined
Dec 10, 2000
Messages
1,490
Likes
1
#7
No, I usually change the sprockets at least once during the life of the chain. Once I can see a little wear on the teeth of the sprockets, I go ahead and change them to prevent them from wearing the chain out. The sprockets are cheap, the chain is not.

RC, I would guess you need a 520 chain, possibly a 110 or 112 link. I haven't had a 125 in almost twenty years, so I can't give you a definite answer on that one. As for the sprocket size, count the number of teeth you have now. If you want to gear it down, add a couple of teeth to the rear, but you may need to order a longer chain to do this. Getting a 1 tooth smaller front sprocket is about the same as adding 3.5 teeth to the rear, but that would be a huge gearing change, probably way too much for a 125.