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Honda Technical Information

Function of carburetor parts
RS125R / RS250R
Basic functions of each parts
Jet needle
  Application of jet needle depends on which carburetor you are using, So please use appropriate jet needle for your carburetor.
Jet needles in Fig(1) and (2) has different length and tapered angles.
Using in appropriate jet needles will cause trouble.
Comparing taper angle α1 α2 α3
(1) 12/34(33)66/2351/1159 124' 239' 115'
(2) R12N(M)-1157D 124' 315' 115'
Comparing length mm A B C D
(1) 12/34(33)66/2351/1159 66 58.9 46.9 30.3
(2) R12N(M)-1157D 65 56.9 46.9 32.8
  (1) for carburetor with PWJ
(2) for PJ short carburetor (Unleaded fuel)
  The difference between 34 (standard) needle and 33 (option) needle for power jet carburetors is that the 33 needle is 0.5mm shorter at the raise of tapers than the 34 needle. That is, the 33 (option) is 0.5 step richer than the 34 (standard) if comparison is made in the same step.
Likewise, in the case of PJ carburetor without power jets, the M (option) is 0.5 step richer than the N (standard)