|
|
jet size questionjawathemutt
@GUEST
|
|
|
|
ive got a set of cbr600 carbs for my 1.8cvh engine ,how do i find out the best jet sizes thanks
|
| |
|
|
|
|
|
Feb 28, 2012 10:06:47 GMT
|
|
Hi, noticed nobody biting on this, There is no chart that can tell you, but if you go back to fundamentals you can work it out, I take it these are Mikuni Cv carbs? Thee are 3 jets that control fuel, Idle, mid and main. Would need to get an idea where the stock setup leaves it and what you want it to do? Usualy an air corrector jet riches up the mid and an increased main will rich up the top end, if you racing you will need a diferent set up to road use and economy. Also how you filter it up will change the mix. Would need more info if you going with this. Andy
|
| |
|
|
Kieran
Posted a lot
Posts: 1,092
|
|
Feb 28, 2012 10:42:20 GMT
|
You have an idle jet, a needle and a main jet on bike carbs. I run 33mm Mikuni carbs on my 1.6 K series powered Skoda Rapid. The general rule of thumb is 4 x the venturi size, rounded up. I tried 140 mains (33 x 4 rounded up) but on the rolling road it was a bit weak so I drilled the main jets to 1.5mm and it seems perfect. I have the needle circlip on the bottom groove with the shim washer underneath and I have the mixture screws 2 turns out from seated. You can also shorten the slide spring so the slides open up a bit quicker, but I havent bother with this yet. Mine runs perfectly!  |
| |
Last Edit: Feb 28, 2012 10:44:41 GMT by Kieran
The Ashby Jackson fleet:-
1979 Mini Clubman 1.8 K series
1978 Skoda 110r Project 130RS K-oupe
1978 Austin Allegro 1500 SDL Estate
1984 BMW K100 Sidecar outfit
1999 Yamaha FZS 1000 Fazer
1991 Kawasaki ZXR400 race bike
2002 Kawasaki ZX9r race bike
|
|
|
|
|
Feb 28, 2012 11:38:21 GMT
|
You need to work it out either by a rolling road session, or on the road with plug chops and pref a stopwatch. Yours are Mikunis I think, and jet size doesn't relate to mm size, sizing is based on a flow rate I believe. At least some of them are like mini venturi shapes so best not hog them out much, better go bigger and keep the shape etc. Keihin jets do directly relate to mm, so a 125 jet equals a 1.25mm drill bit. Nice and easy to play with, with a set of micro bits and an Archimedes drill.  You should synch the carbs before starting too. You can get them very close on the bench by using fine wire (MIG wire or guitar string for instance), or very small ball bearings... set the butterflies to be have the same clearance/drag on the wire, or let the balls pass. Then re-adjust idle. Vac or manometer gauges are the proper thing but the above gets them very close. |
| |
'66 Amazon <-> '94 LS400 <-> '86 Suzuki 1135 EFE
|
|
