CZ Mikuni Jetting Specs as a reference

[Husabergpete]

Based on a 36mm Mikuni for 250 and 400 info supplied by Adrian who got it from a spec sheet from back in the day.

250 Motor

Main 260

Pilot   35

Needle Jet Q 5

Needle  6FJ6   

Slide 1.5
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Alternative from a Euro Web site

Main 250 but not smaller than a 210

Needle Jet  Q 5

Needle 6DP5

Pilot 35

Slide 2.5

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400 Motor

Main 280

Pilot  25

Needle Jet Q 5

Needle 6FJ6

Slide  2.5

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Just about to fit a new 36 Mikuni to a fresh 1973 250 MX. Will give this post some feedback once it is running and if we need to make changes etc

Pete

[GD66]

http://www.braigasen.com/Mikuni_jetting_chart_two_stroke.htm     

Sounds pretty good, Pete.

[tony27]

Have seen the specs off the braigasen site & only some show really lean pilot jets, my 380 uses a #45 in it's 36mm carb which is what the grand prix cycles(moto-x fox) guys suggested in the 70s. 250 was similar
Have a look at www.czmadness.net in specs to find their jetting specs

[Husabergpete]

Now running a 250 Main and the clip one above middle of needle.

Betta

[Tim37]

Hi , I used to race a few CZ,s for about ten years from the early 90s and remember trying all sorts of carb sizes on 250s and 400s , Interesting to hear you have a 36 mm on a 250 ...they need major port and pipe to support a 36 mm a 32 or 34 will make most guys quicker .... I still have a works 250 with a reed and massive ports ...goes best with a 34 for real world riders unless your doing dirt track .   I used to run a 32 on my 360 sidepipe it was fantastic .
Bigger is not always best ...