I have a 2001 CR 125 and it’s not running well. The bottom 1/4 to 1/2 of the throttle runs like a champ. When I get on it trying to accelerate and pull to over half throttle instead of screaming like it should zzzaaaAAAAAAAA...
I get a zzzaaaa..aaa..aa..aaa..aa..aaa like it is cutting out and it never really reaches it's top end. This is my first dirt bike so I’m relatively new to tuning these things, but I was thinking this meant it was running to rich? So I should try a smaller main jet (larger main just number) and/or moving the needle clip position up. Any other thoughts or suggestions?
Thanks.
Haha thats some way to explai
Haha thats some way to explain the way it sounds. So its boggin?? Are you getting oil coming out the exhaust?? Jetting too rich will make alot of sponge. What you oil mix to the fuel your running??
running rich...
I'm running 50/1 with honda synthetic oil. If it's too rich could that be a sign that the top end needs to be replaced? I guess I'll keep trying to lean it out with the main jet and needle clip possition.
50:1 is lean enough. I mix 40
50:1 is lean enough. I mix 40:1-45:1 myself keeps everything nice and lubed. No if its to rich its just down to the jetting. Your mix is grand. Have you the stock carb settings for the bike. I'll try get you them if you dont.
wow i mix 32:1. and yah
wow i mix 32:1. and yah sounds like a prob in ur carb. take it apart and clean it really good.
carb settings...
Ya, main jet is 380, fuel air mix is 2 and 1/4 turns out, needle clip possition is in the middle for stock settings.
I've dropped the main jet to 360, mix scew is 2.5 turns out, and the needle clip is all the way at the top to try and lean it out. Managed to loose my idle speed screw when I didn't tighten it all the way before testing the bike, so I'm done for the day as far as tuning goes...
Compression
I'm a little concerned that maybe I'm not getting enough compression, would that be causing some of these issues? Any idea where you can get a cheap pressure gage and fitting that will screw into the plug hole so I can check my compression? Otherwise I have to pay a shop $40 to check it...
your your main jet and your c
your your main jet and your clip might be to lean. because the engine doesnt have any fuel to run on its just cutting out. i had the same problem with my 125 until i put a larger main jet in. And your mix might be a little to lean, you should prob put more oil in it if you dont want to replace the top end all the time
and dont mess with your pilot
and dont mess with your pilot air screw or pilot jet if it is running fine in the lower throttle ranges because these dont come into play when the thrittle is opened up. only the needle clip and the main jet are used in higher throttle conditions.
main jet...
Do you recal how much larger main jet you put in? I have noticed very little difference going from a 380 to a 370 to a 360. I'm all for trying a larger one, but how much larger will make a noticable difference? Althogh if my jets are all to lean maybe that's why I don't notice a difference.
Start by bringing everything
Start by bringing everything back to stock settings and then tell us if it is working, It should def work with stock settings. If it does not its another prob.
i only put in one size bigger
i only put in one size bigger. And your main jet is only used when the throttle is opened all the way up, wich is where your problem seems to be. And wher do you live and how hot and humid is it where you live. because bikes are sensitive to elevation and humidity changes. Changing the needle clip will also change how lean and rich it is from about 3/8 to 6/8 throttle so you should try changing that to