Dirt Rider Magazine

Hello,
What mixture ratio should I use if im doing mostly trail riding? Currently alot of parts have been replaced on the bike when I bought it... but how long should I replace parts after riding?[piston rings, blah blah]
Please list what parts and how many hours.

Thanks mate,
Okay.. the only thing I was confused about.. is the last paragraph?

The higher rpm of the YZ demands a little more lubrication - I'd stay with the 32:1 ratio.

As for the last paragraph - not sure which part you were confiused about so I'll cover the whole thing:

These bikes are more durable than you might think. (they are durable)
Using the standard "ring every 20 hours, piston/bearing/pin every other ring change" rule would be a good schedule (it's typical with a 2 stroke to change the ring after every 20 hours of riding, and change the whole topend after every 40 hours. So... at the 20 hour mark, you change the ring, and at the 40 hour mark you change the whole topend, then at the 60 hour mark, change the ring, and at the 80 hour mark, the whole topend... and on and on)
- You can stretch it longer, but the parts for this bike are cheap and it's so easy to work on! (you can go longer than 20 hours on a ring, but the parts are so cheap, and the job is so simple, it's not worth taking the chance)

BTW - it will last longer if you run it a little on the rich side. If you're at sea level that means run a 138 main, needle in the 2nd clip, and a 42 pilot. :

(By rich, I meant Air/Fuel ratio.. at sea level you can run this bike with a 135 main jet - which is leaner than stock - and it will perform very well, but it will wear through rings more quickly, so if you are at sea level, you should probably run it a little rich by using the 138 main - which is the stock main jet. The stock jet needle should also be in the 2nd clip (shich is where it was from the factory, and also a littel on the rich side), and use the #42 pilot jet.

That help?

Cheers..

Good luck!

You've pretty much got it!
There is only one ring, btw - pretty simple!

You can certainly make an argument for running 40:1 if all you are doing is trail riding. If you aren't running the engine hard, it probably won't hurt anything. However, 32:1 provides more lubrication, and this is important for an engine that's already a screamer by nature. Also, the 32:1 provides better ring sealing than 40:1.
Thin of it this way - Yamaha engineers built this bike and we should expect that they know best how to run it - they say 30:1/32:1 and that's what most of us run in our YZ85's.
Here's a thought. Use 40:1 the first time around. Then, when you go to change the ring at 20 hours, measure the end gap for wear and write the number down. Then run the next 20 hours (with the new ring) at 32:1. See if you notice any performance or power difference. When the 20 hours is up, check the ring for wear and measure the end-gap. Compare the ring run for 20 hours at 32:1 to the ring run for 20 hours at 40:1. That way you have some scientific and quantifiable way of measuring the difference in wear between 32:1 and 40:1.

No problem! Always glad to help... now remember to always warm it up before you take off, run the BR9EG plug, and keep that air filter clean! And, of course, be safe :)

You're very welcome!

Hope to see you back here soon :) Hopefully with a well-running bike...

many aftermarket ignition systems are made.... a 'map' would be something like "at x rpm's, use y ignition timing".. so basically, each map represents a 'when this condition exists, use this value for xxx"

I can't give your more info than that becaue I really don't mess with the factory ignitions.

Ahh Grasshopper! The secret of the 'kick' :)

1. DO NOT use any throttle when starting it.
2. The choke WILL click - if it doesn't then something is wrong with your choke.
3. With the choke 'clicked' in place, give it a swift kick - but still don't touch the gas - even when it's running. Let it idle on choke for 15-30 secs, then turn the choke off. After that you can blip the throttle to keep it running (if you need to - mine idles fine without it)

Ahh Professional! I tried to not give throttle at first and my choke wont click. I tried to kick it without gas for a while. Bah, Cold start maybe? As it hasnt been kicked in 2 weeks other than yesterday

Btw, My bro starts his yz125 first kick. He tried to start mine (Assuming that he starts his first kick, he can do the same to mine.), even he cant do it.

Step 1: Check plug
Step 2: Service choke linkage
Step 3: Show your bro he isn't the only stud in the house that can start a bike on one kick

:D

Let's get a few more opinions on this - Dave, you've got one of these bikes too - thoughts for our friend here? Woods - batter up! Can ya repost your oft-quoted surefire 2-stroke starting procedure here again for us?

THX

Skip

PS...My advice is to read the manual and half this awnseres itself DOH......

No prob! let us know if you get the choke 'clicking'...

Step by step guide eh? You paying me for this? :D

Do you have a service manual (not the crappy owners - the actual service manual)? If not, ya need one.

You really need to take the carb abart to do the service. I'll get you started though... loosen the screw for the clamp that hold the carb to the reed boot. Now loosen the screw for the clamp that holds the carb to the airbox. Rotate the carb toward you and take the 2 screws off the top of the carb. The top will come off. Pull the spring up with your fingers, compressing it to the carb cover you just took off. The slide will come up and out (be careful not to bend or scrape the needle). You will see a white cup in there - pull it up and it will expose a hole in the slide and in that hole you can see how the throttle cable connects to the slide. Remove the cable from the slide. Now take a digital pic or several of the carb vent lines. Now remove the lines and the fuel line to the carb, and you should be able to remove the carb itself. Inspect the chocke linkage. clean off any dirt and oil it with light multi-purpose oil. If that doesn't solve your problem, then you really are going to need the manual to disassemble the carb. I'm hoping that a good cleaning and librication will fix it though.

Good! You'll really need it to properly maintain your bike.

All I did to mine was add 1 tooth to the rear sprocket.
There really isn't much low-end power, but the mid and top are plenty strong.

You should be running the BR9EG plug, and using a premix ratio at 32:1 - that alleviates most of the plug fouling issue with this bike. Adding a tooth to the rear puts you up higher in the powerband and will actually make your bike foul LESS! How cool is that?

Check out my garage to see my ride =]
so how many teeth do I need in total on the rear sprocket? 51 or 52

if u were to get a 52 though
wouldnt that make the top weaker

oh well yea thats what i meant

I have a 47 [Original], 48 [On bike when I bought it], and a 50. The bike came w/ 2 extra's

Okay, well. Im still getting used to being gentle with the throttle... the 48 will do I guess. Thanks Skip =]
I'll make revive this thread if I need more help

hey on my 02 yz85 my main jet is 138 and the pilot 45
the neddle is on the second from the top and has NBKF on it
with the pilot u sed that urs was 42 is that stock or did u change the stock to a 42

i kno
cbf makin a new 1