Jump to content
Sign in to follow this  

Quick, Easy 125 2 Stroke Questions

Recommended Posts

I bought a 2003 Yamaha YZ125. I just have a few questions about it because this is my first 2 stroke.

1) I know it a mix. Is 30:1 a good ratio? Also, there is no oil resavoir correct? So I mix the oil/gas and just pour it into the tank?

2) What is the proper way to warm up this bike? Do I let it do it by itself or do I rev it and rev it?

Share this post


Link to post
Share on other sites

1. Do you race? If so, go with 28:1 non-snyth premix. Trail ride? 32:1 should suffice.

2. Dont rev the snot out of it, but vary RPM's while the bike is on the stand for 3 minutes before riding.

Share this post


Link to post
Share on other sites

32:1 premix, that means 4 oz. of oil to every gallon of gas, always run the highest octane gas at the pump. when mixing, use a dark color of oil that way when you shake it up you can pour a little out to see if the gas has a darker tint to it, that means its mixed, but shake for about a min. or so,

also when warming it up. just get it kicked over and barley play with throttle for a bout 30. seconds, then gradually increase the throttle, you will notice that if you rev it to high to quick it sounds muffled but after a few seconds it evens out and sounds normal again, when you Can go thru the whole thing, from no throttle to about 1/2 trottel without any sputtering or muffled sounds the bike is ready to go

Share this post


Link to post
Share on other sites

Yes, i would go with 32:1 premix, with a good oil, and with 91 + octane. Warm it up with choke for about 15 seconds, then turn it off. Vary the throttle (not much than 1/4) for about 3 min. The tops of the rad. should be hot.

Share this post


Link to post
Share on other sites

28:1 are you joking me?? Run it at 32:1 minimum. Run at least 91 octane. Start it with the choke on giving it no gas, let it run for about a minute at idle, take off the choke, and give it small brips until its nice and crisp on the throttle.

Share this post


Link to post
Share on other sites

coming from a guy who actually owned a 03 yz125, heres what it did,.

i ran it at about 38:1 with AV gas.

to warm it up, start with the choke on, let it idle for about 10 secconds then shut the choke off. play with the throttle for a bit then put put around on the track for about a lap and then shes good to go

Share this post


Link to post
Share on other sites
i was thinkin that to, 28:1 is a littel lean eh?

28:1 is super-de-duper rich. lean would be like 50:1

28:1 means one part oil to 28 parts gas.

50:1 is one part oil to 50 parts gas

get it????

Share this post


Link to post
Share on other sites

I wont get into the oil ratio wars but soon as it fires with the choke I turn the choke off. Play with the throttle a bit and when I can't touch the expansion chamber anymore I take off. Then, give it a min +/- riding to clean it self out before going WFO.

.

Share this post


Link to post
Share on other sites

I would never run anything less than 32:1 in a 125. I guess some on the new 100% synth oils maybe, but certainly not dino oil. More oil = better ring seal = more power as well as a well lubed bottom end. If you dont ride it WOT then 32:1 will be fine.

28:1 is perfectly fine as long as you jet for it. Some of you need to do some homework before commenting.

Share this post


Link to post
Share on other sites

You can not go wrong with the ratio that you mix your bike at as long as it is not super rich or super lean. There is a very wide window of ratio that you can play with. Someone on here said to run at 28:1 other says to run it at 32:1 and I personally run mine at 50:1 with no problems ever. I also know of a guy that uses amsoil premix that lets you get away with 100:1.

For warming it up, some of the people hit it pretty well. Warming up your bike is VERY crucial to your bike lasting a long time I believe. It is better to waste a few minutes warming up the bike and having it run good for a long time than it is that to cut some time each day just so that you can go ride sooner. Kick the bike over with the choke on. When your bike is COLD it needs the choke. If you can start the bike cold with no choke, then you need to rejet. Once you kick the bike over turn off the choke. At this point I hold the throttle ever so slightly above idle. After about thirty seconds, start reving the bike. You do not ever need to go above 1/4 to 1/2 throttle. At first when you start revving the bike, it will bog if you are not smoothe. When it is warmed up, you will be able to get snappy on the throttle and the motor should snap with you. Since it is a two stroke, you are able to put your hand on the exhaust pipe. When this is warm you will have the snap that I mention in the throttle. Your radiator cap will also be warm to the touch at this time.

Share this post


Link to post
Share on other sites
28:1 is super-de-duper rich. lean would be like 50:1

28:1 means one part oil to 28 parts gas.

50:1 is one part oil to 50 parts gas

get it????

more oil means less fuel in the mixture which makes it lean.

Share this post


Link to post
Share on other sites

When you say "28:1 is rich" you are refering to the Oil-to-fuel ratio.

I ran 40:1 with Belray Oil in both my 125's and never had a problem. Try a ratio, stick with it and jet properly.

Why 40 to 1? Because I could simply pour 4 gallons of gas into my 5 gallon jug and mix the whole bottle in. No Ratio Rite needed!

Share this post


Link to post
Share on other sites

Thanks for all your responses so far.

I do have another question, however. I know the bike will have some fuel left in it from the previous owner. I went and bought Yamalube semi-synthetic oil today. Now, when I mix my own gas can I simply add it to the gas that he mixed without any problems? Should I empty the remaining gas that was in there and start fresh with my own?

Share this post


Link to post
Share on other sites
I would never run anything less than 32:1 in a 125. I guess some on the new 100% synth oils maybe, but certainly not dino oil. More oil = better ring seal = more power as well as a well lubed bottom end. If you dont ride it WOT then 32:1 will be fine.

28:1 is perfectly fine as long as you jet for it. Some of you need to do some homework before commenting.

Agreed.

Share this post


Link to post
Share on other sites
i was thinkin that to, 28:1 is a littel lean eh?

Umm...Ya the lower the number, the richer it is...It also has to do with your jetting but 28:1 seems to be wayyy too much, you would have oil running out of your silencer and dripping all over your swingarm. I run my bike 40:1 and it's perrrfect

Share this post


Link to post
Share on other sites
I would never run anything less than 32:1 in a 125. I guess some on the new 100% synth oils maybe, but certainly not dino oil. More oil = better ring seal = more power as well as a well lubed bottom end. If you dont ride it WOT then 32:1 will be fine.

28:1 is perfectly fine as long as you jet for it. Some of you need to do some homework before commenting.

You are kidding me right?...Your ring will not seat correctly if you use a ton of oil...Or course I do not know what your jetting is like, but my bike is dialed and trialed...And how would you get more horsepower with more oil?...It will be bogging like an sob, your powervalves would be gunked up to the moon

Share this post


Link to post
Share on other sites

Someone posted about the Amsoil 100:1, a warning:

Never mix a 100:1 fuel ratio unless you actually use the oil made by Amsoil, called "100:1". Don't try this with regular oil.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×