92 RM 125 Bottom end woes

[Bryan1864]

I have a 92 RM 125 that absolutely falls on its face at anything below say 5000rpm. The main jet is a 410 the idle jet is a 40 and the needle is a 6aej1-62. I have no idea what the needle jet is. It has the stock pipe and silencer. This bike won't even idle once it is good and warmed up. I don't race this bike, I want to use it for trails and basic fun riding. I am considering putting on a FMF Fatty pipe with a FMF spark arrester and V Force reeds and cage. Any assistance would great.

 

[ride_red_15]

try playing with your air screw, and cleaning out your carb, maybe hotter spark plug, top end, maybe some porting?

 

[MXP1MP]

First off don't worry about getting after market parts for it right now making it run right is your #1 pirority. It sounds like maybe the float hieght is out of adjustment. How does it run off the bottom is it burbling? bogging? it sounds like its loading up. Check for air leaks while your at it, is it hard to start? how many hours on the top end? etc.

 

[Bryan1864]

I cleaned the carb and changed the idle jet from a 30 to the 40, I also adjusted the air screw out to 1 1/2 turns. This did help some.There is no burbling, it will bog if I ride it for more than about a minute below 1/2 throttle. The bike starts within about two to three kicks. It will foul the plug in about 3-4 hrs of riding if it's not riddin wide open.

 

[1999RM125]

if its too rich right now, why would you go and change the idle jet from a 30 to the 40?

 

[Bryan1864]

I have been experiminting with the jetting and the 40 seemed to help a little. The other thing I just discovered is that the carb has been bored from a 35mm to a 38mm. The neadle is the same size as used on the RM250. Would going back to the stock neadle size help matters or not.