Mikuni Carby Jets

[yzhilly]

I was  trying to figure out Pilot Jet Sizes , My YZ400E lists, #60 pilot standard  .YZ125H #80 ,YZ465H #45 pilot .To richen the mixture on the pilot jet do you go a lower number jet with a larger hole ?.  Main jet   bigger # = more fuel ,bigger hole .  Pilot jet i am now confused .

[Maico31]

A lower number pilot jet is a smaller hole. Pretty much all the bikes back then came out too rich with too large a pilot jet.

[yzhilly]

Thanks for that .The massive one in the 125 have stuffed !!!.

[Freakshow]

little number = little fuel.
more number = more fuel


as a basic rule you will find the Muk hex jets will be a value in flow per minute , for example  a #210 main jets will flow 210 cc/min

and so on. thats what made the muk so easy to work with simple really :O)

[Freakshow]

heres a chart :O)



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[Freakshow]

Mikuni Pilot Jets
VM22/210     
Most Mikuni Carbs. Sizes #10 - #110.     
Sizes #10 - #40 available in increments of 2.5,  and sizes  #40 - #110 in increments of 5.

 Mikuni Main Jets.
4/042 Large Hex
Fits Needle Jets 159, 166, 176, 183, 188, 192, 193, 205, 211, 224.
Sizes #50 - #200 available in increments of 5, and #200 - #500 in increments of 10,
                     and #500 - #720 in increments of 20.

[Freakshow]

i have a tunning manulal for them if that helps ya.

[Lozza]

Beware though Freaky Mikuni claim a 10% allowable error in jet sizing Also the "tweenie" aftermarket Mikuni jets can be miles out(I've never found this) but seen the effects of what happens when you get a misnumbered aftermarket jet

[Freakshow]

noted LOz.

although i have a A/F in the TM right now and whatever the number may be if its not, its right :O)

[yzhilly]

Thanks for the chart Fraeky . I'm not having any drama's at the moment i was just struggling getting my head around the 125 running a # 80 pilot and  a 490 spec is a #50 as my 400 was running a tiny pilot smaller than a #50 could'nt read the number and the main was a #310. So i am running #50 pilot  #380 main and is now running sweet.

[Freakshow]

i think it has also to do with the cylinders, transfer and all that too. and VM come in Bleed and in normal so differant carb circiutry uses differant # for volume. if it works its right, even the mikuni tuning manual says that