99suzukirider Posted March 31, 2010 So I have been playing around with my jetting and can't seem to get it quite right. What jet set ups do those of you with FMF exhausts on your RM 125s have? I tried with the stock jetting and it ran really rich (180 Main, 55 Pilot). I went to FMF's website and they recommended 168 Main and 50 Pilot that was too lean. I went to a 170 main and 55 Pilot and its perfect from 0-1/4 throttle so I think the pilot is OK. It bogs in the midrange but still seems lean. Per FMF's recommendation I am using the 4th needle position (One richer than stock). The main might be a little bit small as well because it bogged once on a full throttle run but seemed ok after that. Also, I was told I might need a new needle, is that true? My set up is: 1999 RM 125 Complete Rebuild (6 hours tops on top and bottom ends) FMF Fatty Pipe FMF Turbine Core 2 Silencer Stock Reeds Stock everything else. Any help is MUCH appreciated!! Thanks!!! Share this post Link to post Share on other sites
2strokezuke Posted April 1, 2010 Ive never heard of replacing the needle. I would expect it to run a bit lean with FMF recommendations because they use a 50/50 mix of pump race gas. When i ran Avgas and jetted it myself I ended up with 168main 1.5 turns out the mixture and everything else stock, very close to what FMF recommended using the high octane AVgas. I'm pretty sure the 4th positions is the stock position. I would lower the needle down to stock and jet the main first, then worry about the needle position. So for example, try a 175 main with stock needle position and see how it runs. If runs good WOT and the spark plug is the correct color, move on adjusting the middle throttle response with the needle. Share this post Link to post Share on other sites
