What Is Bog?? Jetting Help Rm 125

I'm no expert, but I'll give you my 2c. The best way to describe a lean bog, is if your riding with your fuel off accidentaly, and its kinda runinning "ring-ey" and snappy and when you stab it, it may lurch then go buuuwhhhhaaaaa. Running really rich will make your plugs BLACK and foul when your warming it up, and it will be surgy, hesistent, and slower, and not really rev to as high a RPM. Moving the needle doesnt effect it at Wide open, but basiaclly from like everything in the middle of your throotle movement. Umm theres tons of signs of going rich, the engine will feel more like a 4-stroke than the snappy 125 that it is, it will sound blubbery, and make a kinda, well studdering sound. At wide open its hard to tell that though. What kind of oil are you burning, somtimes gummy high temp oils that are for serious racing will cause the bike to hesistate for a second. Also the exsaust, exspecially at wide open, if you can fly down a road on a calm evening then go back and smell the exsaust, if it smells like theres gas fumes mixed with the oil, it's rich. Hope this helps you diagnose it, as for not likeing the yellow bike, they're all so similar, some people get brand lowalty in their blood and for what? From what I opserve at the track, lots of the best 125A guys, are on RM125s, they make good bikes. Ohh yeah I forgot, spooge, the black stuff that drips out the silencer is a good sign of a rich carb, though a slightly rich carb may not spooge, but a clear nose can smell the gas fumes.

So go down in your main jet size. Move one size at a time so you don't go too lean first time out. Jets are way cheaper compared to a blown engine.
When you whack the throttle wide open quick it seems to not be able to burn all the gas and means it is rich. Your in Colorado and it is high there. I would think a 160 is too rich. You could go to the track and ask other rm guys what they run for their jetting. You may have to change some of the other carb parts too, like pilot, needle, to get the right jetting for a screaming bike. Remember what beefy dog said about when a bike is too lean it will seem very responsive and powerful, but don't be fooled, since it will blow your engine. The other carb parts are tested with different throttle settings, but the main jet is critical since you may be on that more than any other jet.

goto www.eric-gorr.com and he has a good jetting guide, you can get your bike to not smoke and never foul a plug.

Remember what beefy dog said about when a bike is too lean it will seem very responsive and powerful, but don't be fooled, since it will blow your engine.


I dissagree, in that if properly jetted, a two-stroke SHOULD be very responsive, and powerful. Usually, a lean condition will cause a loss of power, a "ringy" sound to the exhaust, and surging at a steady midrange throttle setting. A bog a WOT can also be a lean condition, in that the engine is asking for more fuel. And if you can't tell a difference while turning your air screw in & out, your pilot jet is probably either too large, or too small. AND.....a well jetted 2-stroke should have little or no spooge, if using a good quality premix oil, and providing that the bike is being ridden in similiar conditiond, ie temperature, altitude, humidity, etc.

Check out the link below for a VERY comprehensive, and easy to understand jetting lesson.

http://justkdx.dirtrider.net/carbtuning.html

You are at a high elevation, so most all of your jetting is probably rich. Don't be scared of taking on the jetting of your bike. Read the articles above and do it yourself. The jets are cheap and you will learn in the process of doing. $60 is way too much and may not even be correct at the end of the day.
Find some other riding buddies and ask them. The have probably gone through the same thing since they also live at 6k.