CR125 2003 Tuning Questions

[Holly Crap]

So I just bought a 2003 CR125 and have been running it hard. It is a great bike but could be better.

Here is the deal. I am running 40:1. Which would be running one bottle of Red Line premix and 5 gallons Premium fuel. I haven't done a thing to it until yesterday when I put on a FMF Turbine Cire II Spark Arrestor. This is all of the MODS.

Now my problem is getting it fine tuned. It bogs a little bit in the low end when I open it wide open (coming out of a turn on a MX track). Now I know I have to re-jet it. I have been holding of just a little bit to make sure it is completly broken it and running real strong. I know it must be rejetted do to the bog in the low end along with the oil it is spewing out the pipe. When I say this I don't mean a whole lot of oil. Here is an example after installing this brand new FMF pipe yesterday I rode it for maybe one hour straight and took a break. I was just looking at the back of the pipe and there is a drip of oil coming out the back and the inside of the number plate has a pretty good spray of this. Still very minor.

So what I need to know is.

1.) When I bike is running prefectly to the best of it's ability should there be any oil exsiting your pipe. I thought it should be completly CLEAN.

2.) Where do I start?

3.) Change my fuel mixtrue?

4.) Re-jet? If so how is the correct way to do this?

5.) How should I go about all of this?

I plan on riding this bike mainly on the track (MX). I live here in the East Bay Area (East of San Fransisco) CA. If you were needing this to help me. I appreciate any help you can give me. I am sure I can figure this out on my own, I just don't want to make any mistakes with this NEW bike.

Thanks,
Dan

 

[atc3434`]

I wouldn't use any less oil in your mixture, 40 to 1 is about right for a 125. Also, jetting being spot on, a little spooge (oil) out the exaust is still possible, depending on the oil your running. Completely clean exaust on a small bore 2 stroke is really pretty tough. Your case of spooge suggests that your jetting is too rich. I'm going to give you a link to Eric Gorr's guide to carberators and jetting, that is on his website. In it you'll find everything you need to properly jet your bike. Also, about the low end bogging, the CR125 seems to have the weakest, if not non-exsistent, lowend of all the newer 125s. At a low rpm, opening the throttle wide open isn't going to do much for you. But get your jetting straightend out first, and then worry about the low end. A little more clutch and a few more teeth on the rear sproket could be helpful for your low end, but jetting is always the place to start. Here is the link: Eric Gorr's Carb Tuning Guide

Good Luck!

 

[Holly Crap]

Wow...Thanks for the tips and the link to the site. This is what I have been looking for. A site to teach me every thing there is to know about the 2 stroke engine. Along with how to work, maintain, and optimize the engine.

If you have any other links of this nature, that would be great.

Thanks again.

 

[marcusgunby]

Rich has stated that some fuels will not completely vaporise and so you will get a small amount of spooge no matter what jetting you try.If its a very small amount then its not worth the hassle.

 

[UKcr125rider]

I had the low end bogging problem with mine. It's down to having too lean a pilot jet. I put the 32.5 pilot in and adjusted the air screw a bit and it was gone. I also went from a 430 to a 450 main as i've got a v-force and HGS system on it. and thats what i needed to do. Try going up to a 53 tooth rear spkt and that'll help the low end lift!