Jump to content
Sign in to follow this  

Carb swap 2004 Rm144 mikuni tm 38mm

Recommended Posts

Need help with carb tuning. I have an 04 Rm125 bored to 144 with new mikuni tm38. Bike has vforce reeds and fmf fatty with the shorty pipe. Location is South Alabama and temp averages 90 degrees. Current setup is 30 pilot, 375 main with needle on position 3. Bike will not idle and sputters down low but seems to have ample power  from quarter throttle to full. Pretty new to these bikes so any help will be greatly appreciated. The guy i got the bike from had all the work done minus the new carb.

Share this post


Link to post
Share on other sites

I don't have a clear jetting recommendation, however when I did my RM300 over bore I did have to go leaner on the main by 2 sizes and 1 lower (richer) on the needle (was at 2 moved it to 3).  Yes, overbores do tend to need leaner jetting as they pull harder on the carb, you may need a similar change.  When I had it I also tried a 36mm carb off a KTM300, bought a JD Jet kit for it that covered the 300XC models and it worked like a charm.  With that in mind if you can't figure it out on our own then also consider what other 144cc MX bikes that use the same carb are running for jetting and that should at least get you close.

Share this post


Link to post
Share on other sites

Thanks for the info, and this could be the problem also as i think i may have been told wrong on the jetting. Does the smaller the number mean the jet is larger Meaning more fuel? With the higher number the smaller with less fuel flow? 

Share this post


Link to post
Share on other sites

Higher number = larger orifice = more fuel flow

 

A big bore has a higher vacuum signal so it pulls in more fuel from the same size jet as a standard bore,

reason that most require leaner than stock settings.

 

Before fine tuning the jetting, make sure everything else is healthy:

serviced air filter, correct float level, good silencer packing, no air leaks etc etc.

Edited by mlatour

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...