YZ250 Jetting Problems

[CApilot]

I have two 2004 YZ250's, one is stock, except for FMF Turbin Core 2 silencer, jetting is right out of the book, pilot jet 50, needle second notch, main 178. Runs strong, still possibly a little rich. The other bike has the same silencer, and also has the FMF Fatty pipe. This bike is apparently running really rich, lots of spooge and wet plugs, and I have noticed smoke coming from the powevalve vent line. I have the pilot jet down to 45, and still seems rich. Is this normal for these bikes jetting to be so different, and should I continue to try to go smaller on the pilot. Or is there something else wrong.

 

[Rcannon]

I wonder if the bike running rich might have a chipped reed????

 

[SpectraSVT]

To add to your confusion, I have 2003 (same engine as 04) with Factory Fatty. I get smoke from the vent line also but my bike is running lean. Fmf reccommends 178 main needle in 3rd pos. and a 50 pilot. I run 178 main 2nd clip pos. and a 52 pilot. Its running lean. The bike surges in the midrange. But if I put the needle in the 3rd clip pos. to fatten up the midrange the pilot is too fat. And the bike won't stay on during idle with a leaner 50. 48 pilot makes it rev out like its sucking air in massive amounts, won't shut off with kill switch.

Only thing I have left to try is a 180 main. and if that don't work I may just dump the stupid FMF and go with the PC Platinum I had before. Never had one issue with the PC pipe. The FMF has been a headache from day 1...

 

[CApilot]

I'll try a couple of more things, and I was thinking of putting the stock pipe back on and see what that does. Thanks for the info

 

[sodflyer]

Check out this thread on my 04 YZ250...maybe it might help out a little. Jeff.


http://dirtrider.net/forums3/showthread.php?t=104368

 

[steve125]

For whatever its worth here's my jetting spec for my 05YZ250. Jetted at sea level, to 500ft. VP ultimate 4 race fuel.

60 degrees and above
165m
std needle 2nd clip
45 pilot
air screw 2.0 out

40-60 degrees
168/170
std needle 3rd clip
45 pilot
air screw 1.5 to 1 3/4

Both settings, no idle is run, idle screw backed out untill slide closes.

 

[gonzo843]

Have you opened up and degunked the powervalve?

 

[CApilot]

I plan to check the reeds when I get a chance, and while I'm doing that I will check the powervalve, and clean it up if it needs it, Will give it another try this weekend, thanks for the input everyone