Ffffed up the jetting on my rm125

[Tazdeviloo7]

Fouling plugs then can't get it started

I have a 2000 rm125 and I kept fouling out plugs one after another today. I think it's because I used a 5050 oil mix of yamalube 2r and wallmart outboard 2 cycle. I was running it a little rich on oil too. I just got a new fmf fatty pipe and my last pipe was a majorly dented stock one. I've been cheap and using br8es plugs instead of the the 25$ NGK R6918B-8. My bike was also sitting in a garage for half a year and the last time wit was ridin was in the summer, now it's really cold and there's a foot and a half of snow. I also noticed that my bike was spitting out oil and I think it's running too rich. Anybody have a diagnosis to this problem? Is it a good idea to turn the idle up high when I try to start it tomorrow?

 

[Tazdeviloo7]

I just found out I have no school tomorrow and I really want to ride. Can anybody give me like a step to step guide?

 

[Tazdeviloo7]

I just read my clymer manual and found the section where it explains the air/fuel mixture thing and where it is and how to set it. Nevermind my previous questions. Is it a good idea to set the idle really high when trying to get it started? Any tips or suggestions on what or what not to do? Is the ngk br8es a good substitute for the ngk R6918B-8?

 

[MOTOX888]

no it is not a good subsitute..........unless you dont mind breaking off the electrode and rebuildoing the motor!!! The rm bikes have vibrations that cause the electrode to break off.

 

[keithb7]

Search for the word jetting on this forum. There is a ton of info on this forum. Having someone type step by step instructions is redundant. Turning up your idle before attempting to start the bike won't do a heck of a lot. Turn the choke on, then start the bike. If you turn up the idle, all that will happen is once the bike starts up it will idle fast. You do have jetting problems. It is running too rich. Re jetting involves getting into the bottom of your carburetor bowl, removing current jets, read the number on them and then get smaller ones. If you are comfortable doing this, go for it. - Keith

 

[Chili]

While you are getting your jetting squared away I would use BR8ES or BR8EG plugs. Once you get the jetting dialed go back to the proper plug for a margin of safety.

 

[dales298]

If you mix two different oils together you are asking for a fouled plug.

Dale

 

[Tazdeviloo7]

If I just run it with a 40:1 gas oil ratio will this fix most of the problem? Do I have to rejet or can I just lean out the air/fuel mixture screw?

 

[TimberPig]

If you mix two different oils together you are asking for a fouled plug.

Dale

Unless you are mixing significantly different oils, this unlikely. Virtually all modern oils mix without issue, unless you are trying to mix castor and synthetic or something. It is better to use the same oil for consistency though.

Poor jetting causes way more fouled plugs than the oil used, or the mix ratio used.

As to whether you can adjust your mix ratio and play with the air screw. No it will not lean it out. Going to 40:1 will actually richen the jetting slightly, and make your problem worse, not better. The air screw will only lean out the pilot circuit, not the needle, or mains, so no, you have to rejet the bike properly to solve this problem.

Get some fresh mix with only one type of oil, a box of plugs, and jets a couple sizes smaller than what is in there now, and start tuning until it is correct. There are very good instructions floating around here on how to correctly jet your bike, run a search, find them, and then tune your bike from there.