I’ve pulled the tank and airbox off to investigate the poor starting on my MC22. Whilst I am in there what parts on the carbs as a minimum should I look to change to prevent problems in the future? From what I have read the carb. insulators go hard and crack so I should do those. I am going to check that the jetting is suitable for the current set-up using this guide - http://mootavic.olilolo.com/mods/tune.html What else? Are there any other seals/o-rings/gaskets etc. which have a history of problems? Thanks in advance.
IMHO First and most importantly, check the compression. Rings are never going to last long in an engine that does such high rpm. Check valve clearances - I would set them at the largest clearance Replace all the seals and o-rings in the carburettors (including airbox seals). Do you really believe they last thirty years? Check diaphragms Check float valves set the jetting and needle position to standard synchronise idle settings with Morgan Carbtune, or mercury gauges. set pilot mixture by ear, failing that, to factory setting, or by varying from factory by 1/4 turn at a time and seat of pants replace air cleaner element if needed Without extensive documented evidence, and my own confirmation, I would ignore any advice to change the jetting. Cheers Blair
Without any dyno chart proof I can see a lot of HP lost in this dribble. Do as Malestrom says first and start with checking compression and stock jetting and don't under any circumstances use 'pod' filters with your CV carbs.
https://litetek.co/Carb_Kit_Honda_CBR250RR_MC22.html Carburettor Synchronisation (max difference) : 40mmHg Carburettor ID Code (Keihin): CBR250(F) : VG01A CBR250R(H) : VG03A CBR250R(J+K) : VG05A CBR250RR(L+N) : VP20A CBR250RR® : VP20B Carburettor Throat Diameter : CBR250(F) : 25mm CBR250R(H) : 27mm CBR250R(J+K) : 28.5mm CBR250RR(L+N+R) : 29mm Float Heights (When measured at 30o or needle valve seated and spring NOT compressed): CBR250(F) : 7mm CBR250R(H) : 7mm CBR250R(J+K) : 8mm CBR250RR(L+N+R) : 13.7mm Carburettor Jet Sizes : CBR250(F) ; Main Jet : #85 Pilot Jet : #35 CBR250R(H); Main Jet : #88 Pilot Jet : #35 CBR250R(J+K); Main Jet : #85 Pilot Jet : #35 CBR250RR(L+N); Main Jet : Cylinders 1+4 : #105 Cylinders 2+3 : #102 Pilot Jet : #35 CBR250RR®; Main Jet : Cylinder 1+4 : #112 Cylinder 2+3 : #110 Pilot Jet : #35 Carburettor Pilot Screw Mixture Settings (Stock Air-Filter,Exhaust,Ports,Jets) CBR250(F) + CBR250R(H): 2Ѕ screws CBR250R(J+K) : 1 5/8 screws CBR250RR(L+N) : 1 3/4 screws CBR250RR® : 2 1/8 screws https://2fiftycc.com/index.php?threads/honda-cbr250rr-mc22-specifications.2521/